0.1.4

.github/README.md

@@ -116,7 +116,7 @@ The Style Editor (`ImGui.ShowStyleEditor()`) and the Metrics/Debugger (`ImGui.Sh
 
 ### Getting Started & Integration (Roblox)
 
-With [Wally](https://wally.run) ([4dbug/imgui-luau](https://wally.run/package/4dbug/imgui-luau)): add `ImGui = "4dbug/[email protected].2"` under `[dependencies]` in your `wally.toml`, run `wally install`, then `require(ReplicatedStorage.Packages.ImGui)`. Or from source:
+With [Wally](https://wally.run) ([4dbug/imgui-luau](https://wally.run/package/4dbug/imgui-luau)): add `ImGui = "4dbug/[email protected].4"` under `[dependencies]` in your `wally.toml`, run `wally install`, then `require(ReplicatedStorage.Packages.ImGui)`. Or from source:
 
 1. Build the module: `python3 tools/bundle.py` writes `build/ImGui.luau` (`--no-demo` leaves the demo out) and `build/ImGuiTyped.luau`, a small typed entry module (Luau types for the public `ImGui.*` API, `ImVec2`/`ImVec4` and the flag enums) that requires `build/ImGui.luau` as its child `Impl`. The Wally package and the Rojo projects use that layout, so you get autocomplete and type errors in `--!strict` scripts. The single-file `ImGui.luau` also works on its own, just untyped.
 2. Sync with [Rojo](https://rojo.space): [`default.project.json`](/default.project.json) puts the module in `ReplicatedStorage.ImGui` and the example LocalScript in `StarterPlayerScripts`.

.github/workflows/release.yml

@@ -36,6 +36,11 @@ jobs:
           python3 tools/bundle.py --no-demo dist/roblox-nodemo        # ImGui.luau (library only)
           python3 tools/bundle.py --target love dist/love             # imgui_love.lua (library + demo)
           python3 tools/bundle.py --target love --no-demo dist/love-nodemo
+          # minified variants (comments/whitespace stripped, same code): tools/minify.py
+          python3 tools/minify.py dist/roblox/ImGui.luau dist/ImGui.min.luau
+          python3 tools/minify.py dist/roblox-nodemo/ImGui.luau dist/ImGui-nodemo.min.luau
+          python3 tools/minify.py dist/love/imgui_love.lua dist/imgui_love.min.lua
+          python3 tools/minify.py dist/love-nodemo/imgui_love.lua dist/imgui_love-nodemo.min.lua
 
       - name: Check
         run: |
@@ -45,12 +50,25 @@ jobs:
           sed 's|require(script:WaitForChild("Impl"))|nil|' dist/roblox/ImGuiTyped.luau > /tmp/ImGuiTyped.luau && luau-analyze /tmp/ImGuiTyped.luau
           luajit -bl dist/love/imgui_love.lua > /dev/null
           luajit -bl dist/love-nodemo/imgui_love.lua > /dev/null
+          python3 tools/minify.py --test
+          luau-compile --null dist/ImGui.min.luau
+          luau-compile --null dist/ImGui-nodemo.min.luau
+          luajit -bl dist/imgui_love.min.lua > /dev/null
+          luajit -bl dist/imgui_love-nodemo.min.lua > /dev/null
           python3 tools/test/run.py --main tools/test/scripts/t_readme.luau --frames 30 --quiet --roblox --timeout 300 | tee /tmp/r.txt
           grep -q "README OK" /tmp/r.txt
           python3 tools/test/run.py --main tools/test/scripts/t_cached_window.luau --frames 130 --quiet --roblox --timeout 300 | tee /tmp/c.txt
           grep -q "CACHED OK" /tmp/c.txt
+          MINIFY=1 python3 tools/test/run.py --main tools/test/scripts/t_readme.luau --frames 30 --quiet --roblox --timeout 300 | tee /tmp/rm.txt
+          grep -q "README OK" /tmp/rm.txt
+          python3 tools/test/run.py --main tools/test/scripts/t_fixes.luau --frames 25 --quiet --roblox --timeout 300 | tee /tmp/f.txt
+          grep -q "FIXES OK" /tmp/f.txt
           python3 tools/bundle.py --target love >/dev/null
-          luajit tools/test/love/t_drawhash.lua 60 Widgets,Basic
+          luajit tools/test/love/t_drawhash.lua 60 Widgets,Basic | tee /tmp/h.txt
+          cp build/imgui_love.lua /tmp/imgui_love.lua && cp dist/imgui_love.min.lua build/imgui_love.lua
+          luajit tools/test/love/t_drawhash.lua 60 Widgets,Basic | tee /tmp/hm.txt
+          cp /tmp/imgui_love.lua build/imgui_love.lua
+          diff /tmp/h.txt /tmp/hm.txt   # minified LÖVE bundle draws exactly the same
           luajit tools/test/love/t_examples.lua
 
       - name: Package
@@ -80,6 +98,8 @@ jobs:
             dist/ImGui-nodemo.luau
             dist/imgui_love.lua
             dist/imgui_love-nodemo.lua
+            dist/*.min.luau
+            dist/*.min.lua
             dist/*.zip
           generate_release_notes: true
 
@@ -105,4 +125,4 @@ jobs:
           gh release delete latest --yes --cleanup-tag || true
           gh release create latest --latest --title "Latest build (${GITHUB_SHA::7})" \
             --notes "Automatic build of ${GITHUB_SHA} on ${GITHUB_REF_NAME}. Tag a commit v* for a versioned release." \
-            dist/ImGui.luau dist/ImGui-nodemo.luau dist/imgui_love.lua dist/imgui_love-nodemo.lua dist/*.zip
+            dist/ImGui.luau dist/ImGui-nodemo.luau dist/imgui_love.lua dist/imgui_love-nodemo.lua dist/*.min.luau dist/*.min.lua dist/*.zip

README.md

@@ -113,7 +113,7 @@ The Style Editor (`ImGui.ShowStyleEditor()`) and the Metrics/Debugger (`ImGui.Sh
 
 ### Getting Started & Integration (Roblox)
 
-With [Wally](https://wally.run) ([4dbug/imgui-luau](https://wally.run/package/4dbug/imgui-luau)): add `ImGui = "4dbug/[email protected].2"` under `[dependencies]` in your `wally.toml`, run `wally install`, then `require(ReplicatedStorage.Packages.ImGui)`. Or from source:
+With [Wally](https://wally.run) ([4dbug/imgui-luau](https://wally.run/package/4dbug/imgui-luau)): add `ImGui = "4dbug/[email protected].4"` under `[dependencies]` in your `wally.toml`, run `wally install`, then `require(ReplicatedStorage.Packages.ImGui)`. Or from source:
 
 1. Build the module: `python3 tools/bundle.py` writes `build/ImGui.luau` (`--no-demo` leaves the demo out) and `build/ImGuiTyped.luau`, a small typed entry module (Luau types for the public `ImGui.*` API, `ImVec2`/`ImVec4` and the flag enums) that requires `build/ImGui.luau` as its child `Impl`. The Wally package and the Rojo projects use that layout, so you get autocomplete and type errors in `--!strict` scripts. The single-file `ImGui.luau` also works on its own, just untyped.
 2. Sync with [Rojo](https://rojo.space): [`default.project.json`](default.project.json) puts the module in `ReplicatedStorage.ImGui` and the example LocalScript in `StarterPlayerScripts`.

backends/imgui_impl_roblox.lua

@@ -862,7 +862,8 @@ function ImGui_ImplRoblox_RenderDrawData(draw_data)
     end
     if rate > 0 then
         local now = os.clock()
-        if now + 0.002 < bd.NextRender then table.clear(bd.Overlays); PE(); return end
+        -- Skipped: kept pending, so if no new frame comes (the app stopped rendering) Heartbeat still draws it
+        if now + 0.002 < bd.NextRender then bd.Pending = draw_data; PE(); return end
         bd.NextRender = math.max(bd.NextRender + 1 / rate, now)
     end
 
@@ -1129,6 +1130,16 @@ function ImGui_ImplRoblox_Init(parent, render_scale)
 
     bd.PendingChars = {}
 
+    -- Render rate cap trailing edge: the last frame submitted is always drawn, even if it was skipped and the app
+    -- then stopped calling NewFrame (e.g. it rendered one empty frame to hide its windows)
+    connect(game:GetService("RunService").Heartbeat, function()
+        local d = bd.Pending
+        if d and os.clock() + 0.002 >= bd.NextRender then
+            bd.Pending = nil
+            ImGui_ImplRoblox_RenderDrawData(d)
+        end
+    end)
+
     connect(UserInputService.WindowFocused, function() ImGui.GetIO():AddFocusEvent(true) end)
     connect(UserInputService.WindowFocusReleased, function() ImGui.GetIO():AddFocusEvent(false) end)
 end
@@ -1188,6 +1199,7 @@ function ImGui_ImplRoblox_NewFrame()
     PB("ImGui NewFrame (backend)")
     local io = ImGui.GetIO()
     local bd = ImGui_ImplRoblox_GetBackendData()
+    if bd.Pending then bd.Pending = nil; table.clear(bd.Overlays) end -- skipped frame superseded (its draw lists get reset)
 
     local screen = bd.Gui.AbsoluteSize
     local w, h = floor(screen.X * bd.Scale), floor(screen.Y * bd.Scale)

build/ImGui.linemap.json

@@ -1 +1 @@
-[[12, "imgui.lua"], [18510, "imgui_demo.lua"], [25795, "imgui_draw.lua"], [31033, "imgui_h.lua"], [33231, "imgui_impl_roblox.lua"], [34571, "imgui_impl_roblox_fonts.lua"], [40974, "imgui_internal.lua"], [44150, "imgui_tables.lua"], [48497, "imgui_widgets.lua"], [58252, "imstb_rectpack.lua"], [58698, "imstb_textedit.lua"], [59939, "imstb_truetype.lua"], [62407, "imstd_minstdio.lua"]]
+[[12, "imgui.lua"], [21288, "imgui_demo.lua"], [29706, "imgui_draw.lua"], [35476, "imgui_h.lua"], [38142, "imgui_impl_roblox.lua"], [39494, "imgui_impl_roblox_fonts.lua"], [45897, "imgui_internal.lua"], [49343, "imgui_tables.lua"], [54338, "imgui_widgets.lua"], [64948, "imstb_rectpack.lua"], [65612, "imstb_textedit.lua"], [67154, "imstb_truetype.lua"], [69942, "imstd_minstdio.lua"]]

build/imgui_love.linemap.json

@@ -1 +1 @@
-[[149, "imgui.lua"], [18647, "imgui_demo.lua"], [25932, "imgui_draw.lua"], [31170, "imgui_h.lua"], [33368, "imgui_impl_love.lua"], [33908, "imgui_internal.lua"], [37084, "imgui_tables.lua"], [41431, "imgui_widgets.lua"], [51186, "imstb_rectpack.lua"], [51632, "imstb_textedit.lua"], [52873, "imstb_truetype.lua"], [55341, "imstd_minstdio.lua"]]
+[[149, "imgui.lua"], [21425, "imgui_demo.lua"], [29843, "imgui_draw.lua"], [35613, "imgui_h.lua"], [38279, "imgui_impl_love.lua"], [38819, "imgui_internal.lua"], [42265, "imgui_tables.lua"], [47260, "imgui_widgets.lua"], [57870, "imstb_rectpack.lua"], [58534, "imstb_textedit.lua"], [60076, "imstb_truetype.lua"], [62864, "imstd_minstdio.lua"]]

imstb_rectpack.lua

@@ -4,6 +4,63 @@
 -- ALL TABLES IN THIS FILE ARE 1-BASED!
 -- Avoids table creation when possible
 
+-- [DEAR IMGUI]
+-- This is a slightly modified version of stb_rect_pack.h 1.01.
+-- Grep for [DEAR IMGUI] to find the changes.
+--
+-- stb_rect_pack.h - v1.01 - public domain - rectangle packing
+-- Sean Barrett 2014
+--
+-- Useful for e.g. packing rectangular textures into an atlas.
+-- Does not do rotation.
+--
+-- Not necessarily the awesomest packing method, but better than
+-- the totally naive one in stb_truetype (which is primarily what
+-- this is meant to replace).
+--
+-- Has only had a few tests run, may have issues.
+--
+-- More docs to come.
+--
+-- Uses table.sort and assert (STBRP_SORT and STBRP_ASSERT below).
+--
+-- This library currently uses the Skyline Bottom-Left algorithm.
+--
+-- Please note: better rectangle packers are welcome! Please
+-- implement them to the same API, but with a different init
+-- function.
+--
+-- Credits
+--
+--  Library
+--    Sean Barrett
+--  Minor features
+--    Martins Mozeiko
+--    github:IntellectualKitty
+--
+--  Bugfixes / warning fixes
+--    Jeremy Jaussaud
+--    Fabian Giesen
+--
+-- Version history:
+--
+--     1.01  (2021-07-11)  always use large rect mode, expose STBRP__MAXVAL in public section
+--     1.00  (2019-02-25)  avoid small space waste; gracefully fail too-wide rectangles
+--     0.99  (2019-02-07)  warning fixes
+--     0.11  (2017-03-03)  return packing success/fail result
+--     0.10  (2016-10-25)  remove cast-away-const to avoid warnings
+--     0.09  (2016-08-27)  fix compiler warnings
+--     0.08  (2015-09-13)  really fix bug with empty rects (w=0 or h=0)
+--     0.07  (2015-09-13)  fix bug with empty rects (w=0 or h=0)
+--     0.06  (2015-04-15)  added STBRP_SORT to allow replacing qsort
+--     0.05:  added STBRP_ASSERT to allow replacing assert
+--     0.04:  fixed minor bug in STBRP_LARGE_RECTS support
+--     0.01:  initial release
+--
+-- LICENSE
+--
+--   See end of file for license information.
+
 --- The `prev_link` can be stbrp_context or stbrp_node
 --- @diagnostic disable
 
@@ -13,7 +70,13 @@ local STBRP_SORT = table.sort
 local STBRP_ASSERT = assert
 local STBRP__NOTUSED = function(_) end
 
+-------------------------------------------------------------------------------
+--
+--       INCLUDE SECTION
+--
+
 local STBRP__MAXVAL = 0x7fffffff
+-- Mostly for internal use, but this is the maximum supported coordinate value.
 
 --- @enum STBRP_HEURISTIC_Skyline
 local STBRP_HEURISTIC_Skyline = {
@@ -44,12 +107,17 @@ local STBRP__PREV_LINK_TYPE = {
 --- @nodiscard
 local function stbrp_rect()
     return {
+        -- reserved for your use:
         id         = 0,
+
+        -- input:
         w          = 0,
         h          = 0,
+
+        -- output:
         x          = 0,
         y          = 0,
-        was_packed = 0
+        was_packed = 0 -- non-zero if valid packing
     }
 end
 
@@ -92,7 +160,7 @@ local function stbrp_context()
 
         active_head = nil,
         free_head   = nil,
-        extra       = {stbrp_node(), stbrp_node()}
+        extra       = {stbrp_node(), stbrp_node()} -- we allocate two extra nodes so optimal user-node-count is 'width' not 'width+2'
     }
 end
 
@@ -113,13 +181,14 @@ local function stbrp__findresult()
     }
 end
 
---------------------------
+-------------------------------------------------------------------------------
---------------------------
+--
----
+--     IMPLEMENTATION SECTION
---- IMPLEMENTATION SECTION
+--
----
----
 
+-- Optionally select which packing heuristic the library should use. Different
+-- heuristics will produce better/worse results for different data sets.
+-- If you call init again, this will be reset to the default.
 --- @param context   stbrp_context
 --- @param heuristic int
 local function stbrp_setup_heuristic(context, heuristic)
@@ -131,16 +200,49 @@ local function stbrp_setup_heuristic(context, heuristic)
     end
 end
 
+-- Optionally call this function after init but before doing any packing to
+-- change the handling of the out-of-temp-memory scenario, described above.
+-- If you call init again, this will be reset to the default (false).
 --- @param context          stbrp_context
 --- @param allow_out_of_mem boolean
 local function stbrp_setup_allow_out_of_mem(context, allow_out_of_mem)
     if allow_out_of_mem then
+        -- if it's ok to run out of memory, then don't bother aligning them;
+        -- this gives better packing, but may fail due to OOM (even though
+        -- the rectangles easily fit). @TODO a smarter approach would be to only
+        -- quantize once we've hit OOM, then we could get rid of this parameter.
         context.align = 1
     else
+        -- if it's not ok to run out of memory, then quantize the widths
+        -- so that num_nodes is always enough nodes.
+        --
+        -- I.e. num_nodes * align >= width
+        --                  align >= width / num_nodes
+        --                  align = ceil(width/num_nodes)
+
         context.align = (context.width + context.num_nodes - 1) / context.num_nodes
     end
 end
 
+-- Initialize a rectangle packer to:
+--    pack a rectangle that is 'width' by 'height' in dimensions
+--    using temporary storage provided by the array 'nodes', which is 'num_nodes' long
+--
+-- You must call this function every time you start packing into a new target.
+--
+-- There is no "shutdown" function. The 'nodes' memory must stay valid for
+-- the following stbrp_pack_rects() call (or calls), but can be freed after
+-- the call (or calls) finish.
+--
+-- Note: to guarantee best results, either:
+--       1. make sure 'num_nodes' >= 'width'
+--   or  2. call stbrp_setup_allow_out_of_mem() defined above with 'allow_out_of_mem = true'
+--
+-- If you don't do either of the above things, widths will be quantized to multiples
+-- of small integers to guarantee the algorithm doesn't run out of temporary storage.
+--
+-- If you do #2, then the non-quantized algorithm will be used, but the algorithm
+-- may run out of temporary storage and be unable to pack some rectangles.
 --- @param context   stbrp_context
 --- @param width     int
 --- @param height    int
@@ -160,6 +262,7 @@ function stbrp_init_target(context, width, height, nodes, num_nodes)
     context.num_nodes = num_nodes
     stbrp_setup_allow_out_of_mem(context, false)
 
+    -- node 0 is the full width, node 1 is the sentinel (lets us not store width explicitly)
     context.extra[1].x = 0
     context.extra[1].y = 0
     context.extra[1].next = context.extra[2]
@@ -168,6 +271,8 @@ function stbrp_init_target(context, width, height, nodes, num_nodes)
     context.extra[2].next = nil
 end
 
+-- find minimum y position if it starts at x1
+-- Returns (min_y, waste_area)
 --- @param c stbrp_context
 --- @param first stbrp_node
 --- @param x0 int
@@ -181,7 +286,7 @@ local function stbrp__skyline_find_min_y(c, first, x0, width)
 
     STBRP_ASSERT(first.x <= x0)
 
-    STBRP_ASSERT(node.next.x > x0)
+    STBRP_ASSERT(node.next.x > x0) -- we ended up handling this in the caller for efficiency
 
     STBRP_ASSERT(node.x <= x0)
 
@@ -190,14 +295,19 @@ local function stbrp__skyline_find_min_y(c, first, x0, width)
     local visited_width = 0
     while node.x < x1 do
         if node.y > min_y then
+            -- raise min_y higher.
+            -- we've accounted for all waste up to min_y,
+            -- but we'll now add more waste for everything we've visited
             waste_area = waste_area + visited_width * (node.y - min_y)
             min_y = node.y
+            -- the first time through, visited_width might be reduced
             if node.x < x0 then
                 visited_width = visited_width + node.next.x - x0
             else
                 visited_width = visited_width + node.next.x - node.x
             end
         else
+            -- add waste area
             local under_width = node.next.x - node.x
             if under_width + visited_width > width then
                 under_width = width - visited_width
@@ -223,10 +333,12 @@ local function stbrp__skyline_find_best_pos(c, width, height)
     local best_prev_link = nil
     local best_prev_link_type = nil
 
+    -- align to multiple of c.align
     width = width + c.align - 1
     width = width - width % c.align
     STBRP_ASSERT(width % c.align == 0)
 
+    -- if it can't possibly fit, bail immediately
     if width > c.width or height > c.height then
         fr.prev_link = nil
         fr.prev_link_type = nil
@@ -242,7 +354,8 @@ local function stbrp__skyline_find_best_pos(c, width, height)
     while (node.x + width <= c.width) do
         local y, waste = stbrp__skyline_find_min_y(c, node, node.x, width)
 
-        if c.heuristic == STBRP_HEURISTIC_Skyline.BL_sortHeight then
+        if c.heuristic == STBRP_HEURISTIC_Skyline.BL_sortHeight then -- actually just want to test BL
+            -- bottom left
             if y < best_y then
                 best_y = y
                 best_prev_link = prev_link
@@ -250,7 +363,9 @@ local function stbrp__skyline_find_best_pos(c, width, height)
                 best_x = node.x
             end
         else
+            -- best-fit
             if y + height <= c.height then
+                -- can only use it if it first vertically
                 if y < best_y or (y == best_y and waste < best_waste) then
                     best_y = y
                     best_waste = waste
@@ -266,12 +381,30 @@ local function stbrp__skyline_find_best_pos(c, width, height)
         node = node.next
     end
 
+    -- if doing best-fit (BF), we also have to try aligning right edge to each node position
+    --
+    -- e.g, if fitting
+    --
+    --     ____________________
+    --    |____________________|
+    --
+    --            into
+    --
+    --   |                         |
+    --   |             ____________|
+    --   |____________|
+    --
+    -- then right-aligned reduces waste, but bottom-left BL is always chooses left-aligned
+    --
+    -- This makes BF take about 2x the time
+
     if c.heuristic == STBRP_HEURISTIC_Skyline.BF_sortHeight then
         local tail = c.active_head
         local node_scan = c.active_head
         local prev_link_scan = c
         local prev_link_scan_type = STBRP__PREV_LINK_TYPE.ACTIVE_HEAD
 
+        -- find first node that's admissible
         while tail and tail.x < width do
             tail = tail.next
         end
@@ -280,6 +413,7 @@ local function stbrp__skyline_find_best_pos(c, width, height)
             local xpos = tail.x - width
             STBRP_ASSERT(xpos >= 0)
 
+            -- find the left position that matches this
             while node_scan.next and node_scan.next.x <= xpos do
                 prev_link_scan = node_scan
                 prev_link_scan_type = STBRP__PREV_LINK_TYPE.NEXT
@@ -295,6 +429,7 @@ local function stbrp__skyline_find_best_pos(c, width, height)
                     if y <= best_y then
                         if y < best_y or waste < best_waste or (waste == best_waste and xpos < best_x) then
                             best_x = xpos
+                            -- STBRP_ASSERT(y <= best_y); [DEAR IMGUI]
                             best_y = y
                             best_waste = waste
                             best_prev_link = prev_link_scan
@@ -320,19 +455,29 @@ end
 --- @param height  int
 --- @return stbrp__findresult
 local function stbrp__skyline_pack_rectangle(context, width, height)
+    -- find best position according to heuristic
     local res = stbrp__skyline_find_best_pos(context, width, height)
 
+    -- bail if:
+    --    1. it failed
+    --    2. the best node doesn't fit (we don't always check this)
+    --    3. we're out of memory
     if res.prev_link == nil or res.y + height > context.height or context.free_head == nil then
         res.prev_link = nil
         res.prev_link_type = nil
         return res
     end
 
+    -- on success, create new node
     local node = context.free_head
     node.x = res.x
     node.y = res.y + height
     context.free_head = node.next
 
+    -- insert the new node into the right starting point, and
+    -- let 'cur' point to the remaining nodes needing to be
+    -- stitched back in
+
     local cur
     if res.prev_link_type == STBRP__PREV_LINK_TYPE.ACTIVE_HEAD then
         cur = res.prev_link.active_head
@@ -341,6 +486,7 @@ local function stbrp__skyline_pack_rectangle(context, width, height)
     end
 
     if cur.x < res.x then
+        -- preserve the existing one, so start testing with the next one
         local next = cur.next
         cur.next = node
         cur = next
@@ -352,13 +498,17 @@ local function stbrp__skyline_pack_rectangle(context, width, height)
         end
     end
 
+    -- from here, traverse cur and free the nodes, until we get to one
+    -- that shouldn't be freed
     while cur.next and cur.next.x <= res.x + width do
         local next = cur.next
+        -- move the current node to the free list
         cur.next = context.free_head
         context.free_head = cur
         cur = next
     end
 
+    -- stitch the list back in
     node.next = cur
 
     if cur.x < res.x + width then
@@ -390,6 +540,29 @@ local function rect_original_order(a, b)
     return a.was_packed < b.was_packed
 end
 
+-- Assign packed locations to rectangles. The rectangles are of type
+-- 'stbrp_rect' defined above, stored in the array 'rects', and there
+-- are 'num_rects' many of them.
+--
+-- Rectangles which are successfully packed have the 'was_packed' flag
+-- set to a non-zero value and 'x' and 'y' store the minimum location
+-- on each axis (i.e. bottom-left in cartesian coordinates, top-left
+-- if you imagine y increasing downwards). Rectangles which do not fit
+-- have the 'was_packed' flag set to 0.
+--
+-- You should not try to access the 'rects' array from another thread
+-- while this function is running, as the function temporarily reorders
+-- the array while it executes.
+--
+-- To pack into another rectangle, you need to call stbrp_init_target
+-- again. To continue packing into the same rectangle, you can call
+-- this function again. Calling this multiple times with multiple rect
+-- arrays will probably produce worse packing results than calling it
+-- a single time with the full rectangle array, but the option is
+-- available.
+--
+-- The function returns 1 if all of the rectangles were successfully
+-- packed and 0 otherwise.
 --- @param context   stbrp_context
 --- @param rects     stbrp_rect[]
 --- @param num_rects int
@@ -397,15 +570,17 @@ end
 local function stbrp_pack_rects(context, rects, num_rects)
     local all_rects_packed = 1
 
+    -- we use the 'was_packed' field internally to allow sorting/unsorting
     for i = 1, num_rects do
         rects[i].was_packed = (i - 1)
     end
 
+    -- sort according to heuristic
     STBRP_SORT(rects, rect_height_compare)
 
     for i = 1, num_rects do
         if rects[i].w == 0 or rects[i].h == 0 then
-            rects[i].x = 0
+            rects[i].x = 0 -- empty rect needs no space
             rects[i].y = 0
         else
             local fr = stbrp__skyline_pack_rectangle(context, rects[i].w, rects[i].h)
@@ -419,8 +594,10 @@ local function stbrp_pack_rects(context, rects, num_rects)
         end
     end
 
+    -- unsort
     STBRP_SORT(rects, rect_original_order)
 
+    -- set was_packed flags and all_rects_packed status
     for i = 1, num_rects do
         rects[i].was_packed = (rects[i].x == STBRP__MAXVAL and rects[i].y == STBRP__MAXVAL) and 0 or 1
         if rects[i].was_packed == 0 then
@@ -428,6 +605,7 @@ local function stbrp_pack_rects(context, rects, num_rects)
         end
     end
 
+    -- return the all_rects_packed status
     return all_rects_packed
 end
 
@@ -441,3 +619,43 @@ return {
     setup_allow_out_of_mem = stbrp_setup_allow_out_of_mem,
     setup_heuristic        = stbrp_setup_heuristic
 }
+
+-- ------------------------------------------------------------------------------
+-- This software is available under 2 licenses -- choose whichever you prefer.
+-- ------------------------------------------------------------------------------
+-- ALTERNATIVE A - MIT License
+-- Copyright (c) 2017 Sean Barrett
+-- Permission is hereby granted, free of charge, to any person obtaining a copy of
+-- this software and associated documentation files (the "Software"), to deal in
+-- the Software without restriction, including without limitation the rights to
+-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+-- of the Software, and to permit persons to whom the Software is furnished to do
+-- so, subject to the following conditions:
+-- The above copyright notice and this permission notice shall be included in all
+-- copies or substantial portions of the Software.
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+-- SOFTWARE.
+-- ------------------------------------------------------------------------------
+-- ALTERNATIVE B - Public Domain (www.unlicense.org)
+-- This is free and unencumbered software released into the public domain.
+-- Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+-- software, either in source code form or as a compiled binary, for any purpose,
+-- commercial or non-commercial, and by any means.
+-- In jurisdictions that recognize copyright laws, the author or authors of this
+-- software dedicate any and all copyright interest in the software to the public
+-- domain. We make this dedication for the benefit of the public at large and to
+-- the detriment of our heirs and successors. We intend this dedication to be an
+-- overt act of relinquishment in perpetuity of all present and future rights to
+-- this software under copyright law.
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+-- ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+-- WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+-- ------------------------------------------------------------------------------

imstb_textedit.lua

@@ -1,6 +1,221 @@
 --- Dear ImGui
 -- This is a Lua port of original `imstb_textedit.h`
 
+-- [DEAR IMGUI]
+-- This is a slightly modified version of stb_textedit.h 1.14.
+-- Those changes would need to be pushed into nothings/stb:
+-- - Fix in stb_textedit_discard_redo (see https://github.com/nothings/stb/issues/321)
+-- - Fix in stb_textedit_find_charpos to handle last line (see https://github.com/ocornut/imgui/issues/6000 + #6783)
+-- - Added name to struct or it may be forward declared in our code.
+-- - Added UTF-8 support (see https://github.com/nothings/stb/issues/188 + https://github.com/ocornut/imgui/pull/7925)
+-- - Changed STB_TEXTEDIT_INSERTCHARS() to return inserted count (instead of 0/1 bool), allowing partial insertion.
+-- Grep for [DEAR IMGUI] to find some changes.
+-- - Also renamed macros used or defined outside of IMSTB_TEXTEDIT_IMPLEMENTATION block from STB_TEXTEDIT_* to IMSTB_TEXTEDIT_*
+
+-- stb_textedit.h - v1.14  - public domain - Sean Barrett
+-- Development of this library was sponsored by RAD Game Tools
+--
+-- This C header file implements the guts of a multi-line text-editing
+-- widget; you implement display, word-wrapping, and low-level string
+-- insertion/deletion, and stb_textedit will map user inputs into
+-- insertions & deletions, plus updates to the cursor position,
+-- selection state, and undo state.
+--
+-- It is intended for use in games and other systems that need to build
+-- their own custom widgets and which do not have heavy text-editing
+-- requirements (this library is not recommended for use for editing large
+-- texts, as its performance does not scale and it has limited undo).
+--
+-- Non-trivial behaviors are modelled after Windows text controls.
+--
+--
+-- LICENSE
+--
+-- See end of file for license information.
+--
+--
+-- DEPENDENCIES
+--
+-- Uses the C runtime function 'memmove', which you can override
+-- by defining IMSTB_TEXTEDIT_memmove before the implementation.
+-- (In this port: ImStb.TEXTEDIT_memmove.)
+--
+--
+-- VERSION HISTORY
+--
+--   !!!! (2025-10-23) changed STB_TEXTEDIT_INSERTCHARS() to return inserted count (instead of 0/1 bool), allowing partial insertion.
+--   1.14 (2021-07-11) page up/down, various fixes
+--   1.13 (2019-02-07) fix bug in undo size management
+--   1.12 (2018-01-29) user can change STB_TEXTEDIT_KEYTYPE, fix redo to avoid crash
+--   1.11 (2017-03-03) fix HOME on last line, dragging off single-line textfield
+--   1.10 (2016-10-25) suppress warnings about casting away const with -Wcast-qual
+--   1.9  (2016-08-27) customizable move-by-word
+--   1.8  (2016-04-02) better keyboard handling when mouse button is down
+--   1.7  (2015-09-13) change y range handling in case baseline is non-0
+--   1.6  (2015-04-15) allow STB_TEXTEDIT_memmove
+--   1.5  (2014-09-10) add support for secondary keys for OS X
+--   1.4  (2014-08-17) fix signed/unsigned warnings
+--   1.3  (2014-06-19) fix mouse clicking to round to nearest char boundary
+--   1.2  (2014-05-27) fix some RAD types that had crept into the new code
+--   1.1  (2013-12-15) move-by-word (requires STB_TEXTEDIT_IS_SPACE )
+--   1.0  (2012-07-26) improve documentation, initial public release
+--   0.3  (2012-02-24) bugfixes, single-line mode; insert mode
+--   0.2  (2011-11-28) fixes to undo/redo
+--   0.1  (2010-07-08) initial version
+--
+-- ADDITIONAL CONTRIBUTORS
+--
+--   Ulf Winklemann: move-by-word in 1.1
+--   Fabian Giesen: secondary key inputs in 1.5
+--   Martins Mozeiko: STB_TEXTEDIT_memmove in 1.6
+--   Louis Schnellbach: page up/down in 1.14
+--
+--   Bugfixes:
+--      Scott Graham
+--      Daniel Keller
+--      Omar Cornut
+--      Dan Thompson
+--
+-- USAGE
+--
+--   The basic concept is that you provide a "string" object which
+--   behaves like an array of characters. stb_textedit uses indices to
+--   refer to positions in the string, implicitly representing positions
+--   in the displayed textedit. This is true for both plain text and
+--   rich text; even with rich text stb_truetype interacts with your
+--   code as if there was an array of all the displayed characters.
+--
+-- Symbols you must define for implementation mode (in this port: fields of ImStb, see below):
+--
+--    STB_TEXTEDIT_STRING               the type of object representing a string being edited,
+--                                      typically this is a wrapper object with other data you need
+--
+--    STB_TEXTEDIT_STRINGLEN(obj)       the length of the string (ideally O(1))
+--    STB_TEXTEDIT_LAYOUTROW(r,obj,n)   returns the results of laying out a line of characters
+--                                        starting from character #n (see discussion below)
+--    STB_TEXTEDIT_GETWIDTH(obj,n,i)    returns the pixel delta from the xpos of the i'th character
+--                                        to the xpos of the i+1'th char for a line of characters
+--                                        starting at character #n (i.e. accounts for kerning
+--                                        with previous char)
+--    STB_TEXTEDIT_GETCHAR(obj,i)       returns the i'th character of obj, 1-based in this port
+--    STB_TEXTEDIT_NEWLINE              the character returned by _GETCHAR() we recognize
+--                                        as manually wordwrapping for end-of-line positioning
+--
+--    STB_TEXTEDIT_DELETECHARS(obj,i,n)      delete n characters starting at i
+--    STB_TEXTEDIT_INSERTCHARS(obj,i,c,c_offset,n)   try to insert n characters at i (taken from array c starting at c_offset)
+--                                           returns number of characters actually inserted. [DEAR IMGUI]
+--
+--    STB_TEXTEDIT_K_SHIFT       a power of two that is or'd in to a keyboard input to represent the shift key
+--
+--    STB_TEXTEDIT_K_LEFT        keyboard input to move cursor left
+--    STB_TEXTEDIT_K_RIGHT       keyboard input to move cursor right
+--    STB_TEXTEDIT_K_UP          keyboard input to move cursor up
+--    STB_TEXTEDIT_K_DOWN        keyboard input to move cursor down
+--    STB_TEXTEDIT_K_PGUP        keyboard input to move cursor up a page
+--    STB_TEXTEDIT_K_PGDOWN      keyboard input to move cursor down a page
+--    STB_TEXTEDIT_K_LINESTART   keyboard input to move cursor to start of line  -- e.g. HOME
+--    STB_TEXTEDIT_K_LINEEND     keyboard input to move cursor to end of line    -- e.g. END
+--    STB_TEXTEDIT_K_TEXTSTART   keyboard input to move cursor to start of text  -- e.g. ctrl-HOME
+--    STB_TEXTEDIT_K_TEXTEND     keyboard input to move cursor to end of text    -- e.g. ctrl-END
+--    STB_TEXTEDIT_K_DELETE      keyboard input to delete selection or character under cursor
+--    STB_TEXTEDIT_K_BACKSPACE   keyboard input to delete selection or character left of cursor
+--    STB_TEXTEDIT_K_UNDO        keyboard input to perform undo
+--    STB_TEXTEDIT_K_REDO        keyboard input to perform redo
+--
+--    STB_TEXTEDIT_MOVEWORDLEFT(obj,i)   custom handler for WORDLEFT, returns index to move cursor to
+--    STB_TEXTEDIT_MOVEWORDRIGHT(obj,i)  custom handler for WORDRIGHT, returns index to move cursor to
+--    STB_TEXTEDIT_K_WORDLEFT            keyboard input to move cursor left one word -- e.g. ctrl-LEFT
+--    STB_TEXTEDIT_K_WORDRIGHT           keyboard input to move cursor right one word -- e.g. ctrl-RIGHT
+--
+-- To support UTF-8:
+--
+--    STB_TEXTEDIT_GETPREVCHARINDEX      returns index of previous character
+--    STB_TEXTEDIT_GETNEXTCHARINDEX      returns index of next character
+--    Do NOT define STB_TEXTEDIT_KEYTOTEXT.
+--    Instead, call stb_textedit_text() directly for text contents.
+--
+-- Keyboard input must be encoded as a single integer value; e.g. a character code
+-- and some bitflags that represent shift states. to simplify the interface, SHIFT must
+-- be a bitflag, so we can test the shifted state of cursor movements to allow selection,
+-- i.e. (STB_TEXTEDIT_K_RIGHT|STB_TEXTEDIT_K_SHIFT) should be shifted right-arrow.
+--
+-- STB_TEXTEDIT_LAYOUTROW returns information about the shape of one displayed
+-- row of characters assuming they start on the i'th character--the width and
+-- the height and the number of characters consumed. This allows this library
+-- to traverse the entire layout incrementally. You need to compute word-wrapping
+-- here.
+--
+-- Each textfield keeps its own insert mode state, which is not how normal
+-- applications work. To keep an app-wide insert mode, update/copy the
+-- "insert_mode" field of STB_TexteditState before/after calling API functions.
+--
+-- API (in this port: fields of the table returned by this file)
+--
+--    initialize_state(state, is_single_line)
+--
+--    click(str, state, x, y)
+--    drag(str, state, x, y)
+--    cut(str, state) -> bool
+--    paste(str, state, text, len) -> bool
+--    key(str, state, key)
+--    text(str, state, text, text_len)
+--
+--    Each of these functions potentially updates the string and updates the
+--    state.
+--
+--      initialize_state:
+--          set the textedit state to a known good default state when initially
+--          constructing the textedit.
+--
+--      click:
+--          call this with the mouse x,y on a mouse down; it will update the cursor
+--          and reset the selection start/end to the cursor point. the x,y must
+--          be relative to the text widget, with (0,0) being the top left.
+--
+--      drag:
+--          call this with the mouse x,y on a mouse drag/up; it will update the
+--          cursor and the selection end point
+--
+--      cut:
+--          call this to delete the current selection; returns true if there was
+--          one. you should FIRST copy the current selection to the system paste buffer.
+--          (To copy, just copy the current selection out of the string yourself.)
+--
+--      paste:
+--          call this to paste text at the current cursor point or over the current
+--          selection if there is one.
+--
+--      key:
+--          call this for keyboard inputs sent to the textfield. you can use it
+--          for "key down" events or for "translated" key events.
+--
+--      text: (added 2025)
+--          call this to directly send text input the textfield, which is required
+--          for UTF-8 support, because stb_textedit_key() + STB_TEXTEDIT_KEYTOTEXT()
+--          cannot infer text length.
+--
+--
+--   When rendering, you can read the cursor position and selection state from
+--   the STB_TexteditState.
+--
+--
+-- Notes:
+--
+-- This is designed to be usable in IMGUI, so it allows for the possibility of
+-- running in an IMGUI that has NOT cached the multi-line layout. For this
+-- reason, it provides an interface that is compatible with computing the
+-- layout incrementally--we try to make sure we make as few passes through
+-- as possible. (For example, to locate the mouse pointer in the text, we
+-- could define functions that return the X and Y positions of characters
+-- and binary search Y and then X, but if we're doing dynamic layout this
+-- will run the layout algorithm many times, so instead we manually search
+-- forward in one pass. Similar logic applies to e.g. up-arrow and
+-- down-arrow movement.)
+--
+-- If it's run in a widget that *has* cached the layout, then this is less
+-- efficient, but it's not horrible on modern computers. But you wouldn't
+-- want to edit million-line files with it.
+
 -- ALL TABLES IN THIS FILE ARE 1-BASED!
 -- Character Indexing:
 --     idx=n, the n'th char (1-based)
@@ -13,6 +228,10 @@ local STB_TEXTEDIT_STRINGLEN = ImStb.TEXTEDIT_STRINGLEN
 local STB_TEXTEDIT_GETCHAR   = ImStb.TEXTEDIT_GETCHAR
 local STB_TEXTEDIT_GETWIDTH  = ImStb.TEXTEDIT_GETWIDTH
 local STB_TEXTEDIT_LAYOUTROW = ImStb.TEXTEDIT_LAYOUTROW
+-- [DEAR IMGUI]
+-- Functions must be implemented for UTF8 support
+-- Code in this file that uses those functions is modified for [DEAR IMGUI] and deviates from the original stb_textedit.
+-- There is not necessarily a '[DEAR IMGUI]' at the usage sites.
 local IMSTB_TEXTEDIT_GETNEXTCHARINDEX = ImStb.TEXTEDIT_GETNEXTCHARINDEX
 local IMSTB_TEXTEDIT_GETPREVCHARINDEX = ImStb.TEXTEDIT_GETPREVCHARINDEX
 local STB_TEXTEDIT_MOVEWORDLEFT  = ImStb.TEXTEDIT_MOVEWORDLEFT
@@ -22,34 +241,35 @@ local STB_TEXTEDIT_MOVELINEEND   = ImStb.TEXTEDIT_MOVELINEEND
 local STB_TEXTEDIT_DELETECHARS   = ImStb.TEXTEDIT_DELETECHARS
 local STB_TEXTEDIT_INSERTCHARS   = ImStb.TEXTEDIT_INSERTCHARS
 
-STB_TEXTEDIT_NEWLINE     = 10
+STB_TEXTEDIT_NEWLINE     = 10 -- the character returned by _GETCHAR() we recognize as manually wordwrapping for end-of-line positioning
 STB_TEXTEDIT_K_LEFT      = 0x200000 -- keyboard input to move cursor left
 STB_TEXTEDIT_K_RIGHT     = 0x200001 -- keyboard input to move cursor right
 STB_TEXTEDIT_K_UP        = 0x200002 -- keyboard input to move cursor up
 STB_TEXTEDIT_K_DOWN      = 0x200003 -- keyboard input to move cursor down
-STB_TEXTEDIT_K_LINESTART = 0x200004 -- keyboard input to move cursor to start of line
+STB_TEXTEDIT_K_LINESTART = 0x200004 -- keyboard input to move cursor to start of line  -- e.g. HOME
-STB_TEXTEDIT_K_LINEEND   = 0x200005 -- keyboard input to move cursor to end of line
+STB_TEXTEDIT_K_LINEEND   = 0x200005 -- keyboard input to move cursor to end of line    -- e.g. END
-STB_TEXTEDIT_K_TEXTSTART = 0x200006 -- keyboard input to move cursor to start of text
+STB_TEXTEDIT_K_TEXTSTART = 0x200006 -- keyboard input to move cursor to start of text  -- e.g. ctrl-HOME
-STB_TEXTEDIT_K_TEXTEND   = 0x200007 -- keyboard input to move cursor to end of text
+STB_TEXTEDIT_K_TEXTEND   = 0x200007 -- keyboard input to move cursor to end of text    -- e.g. ctrl-END
 STB_TEXTEDIT_K_DELETE    = 0x200008 -- keyboard input to delete selection or character under cursor
 STB_TEXTEDIT_K_BACKSPACE = 0x200009 -- keyboard input to delete selection or character left of cursor
 STB_TEXTEDIT_K_UNDO      = 0x20000A -- keyboard input to perform undo
 STB_TEXTEDIT_K_REDO      = 0x20000B -- keyboard input to perform redo
-STB_TEXTEDIT_K_WORDLEFT  = 0x20000C -- keyboard input to move cursor left one word
+STB_TEXTEDIT_K_WORDLEFT  = 0x20000C -- keyboard input to move cursor left one word -- e.g. ctrl-LEFT
-STB_TEXTEDIT_K_WORDRIGHT = 0x20000D -- keyboard input to move cursor right one word
+STB_TEXTEDIT_K_WORDRIGHT = 0x20000D -- keyboard input to move cursor right one word -- e.g. ctrl-RIGHT
 STB_TEXTEDIT_K_PGUP      = 0x20000E -- keyboard input to move cursor up a page
 STB_TEXTEDIT_K_PGDOWN    = 0x20000F -- keyboard input to move cursor down a page
-STB_TEXTEDIT_K_SHIFT     = 0x400000
+STB_TEXTEDIT_K_SHIFT     = 0x400000 -- a power of two that is or'd in to a keyboard input to represent the shift key
 
-IMSTB_TEXTEDIT_UNDOSTATECOUNT = 99
+IMSTB_TEXTEDIT_UNDOSTATECOUNT = 99 -- the number of undo states to allow
-local IMSTB_TEXTEDIT_UNDOCHARCOUNT  = 999
+local IMSTB_TEXTEDIT_UNDOCHARCOUNT  = 999 -- the number of characters to store in the undo buffer
 local IMSTB_TEXTEDIT_memmove = ImStb.TEXTEDIT_memmove
 
+-- forward declarations
 local stb_text_undo
 local stb_text_redo
 
-----------------------------------------------------------------
+-------------------------------------------------------------------------------
-----------------------------------------------------------------
+-------------------------------------------------------------------------------
 ---
 --- STB_TexteditState
 ---
@@ -72,6 +292,7 @@ local stb_text_redo
 --- @nodiscard
 local function StbUndoRecord()
     return {
+        -- private data
         where         = 1,
         insert_length = 0,
         delete_length = 0,
@@ -101,6 +322,7 @@ local function StbUndoState()
     end
 
     return {
+        -- private data
         undo_rec        = undo_rec,
         undo_char       = undo_char,
 
@@ -131,16 +353,34 @@ end
 --- @nodiscard
 function STB_TexteditState()
     return {
-        cursor = 0,
+        ---------------------
+        --
+        -- public data
+        --
 
-        select_start = 0,
+        cursor = 0,
+        -- position of the text cursor within the string
+
+        select_start = 0, -- selection start point
         select_end   = 0,
+        -- selection start and end point in characters; if equal, no selection.
+        -- note that start may be less than or greater than end (e.g. when
+        -- dragging the mouse, start is where the initial click was, and you
+        -- can drag in either direction)
 
         insert_mode = false,
+        -- each textfield keeps its own insert mode state. to keep an app-wide
+        -- insert mode, copy this value in/out of the app state
 
         row_count_per_page = 0,
+        -- page size in number of row.
+        -- this value MUST be set to >0 for pageup or pagedown in multilines documents.
 
-        cursor_at_end_of_line = false,
+        ---------------------
+        --
+        -- private data
+        --
+        cursor_at_end_of_line = false, -- not implemented yet
         initialized           = false,
         has_preferred_x       = false,
         single_line           = false,
@@ -148,7 +388,7 @@ function STB_TexteditState()
         padding2 = 0,
         padding3 = 0,
 
-        preferred_x = 0.0,
+        preferred_x = 0.0, -- this determines where the cursor up/down tries to seek to along x
 
         undostate = StbUndoState()
     }
@@ -159,12 +399,20 @@ local function STB_TEXT_HAS_SELECTION(s)
     return s.select_start ~= s.select_end
 end
 
+-------------------------------------------------------------------------------
+---
+--- StbTexteditRow
+---
+--- Result of layout query, used by stb_textedit to determine where
+--- the text in each row is.
+
+-- result of layout query
 --- @class StbTexteditRow
---- @field x0               float # starting x location
+--- @field x0               float # starting x location, end x location (allows for align=right, etc)
 --- @field x1               float # end x location
 --- @field baseline_y_delta float # position of baseline relative to previous row's baseline
---- @field ymin             float # height of row above baseline
+--- @field ymin             float # height of row above and below baseline
---- @field ymax             float # height of row below baseline
+--- @field ymax             float # height of row above and below baseline
 --- @field num_chars        int
 
 --- @return StbTexteditRow
@@ -196,10 +444,15 @@ end
 ----------------------------------------
 ----------------------------------------
 ---
---- Implementation
+--- Implementation mode
 ---
 ---
 
+-------------------------------------------------------------------------------
+---
+---      Mouse input handling
+---
+
 local stb_text_locate_coord do
 
 -- only create once, reuse later
@@ -351,6 +604,7 @@ end
 ---
 ---
 
+-- forward declarations
 local stb_text_makeundo_insert
 local stb_text_makeundo_delete
 local stb_text_makeundo_replace
@@ -399,8 +653,8 @@ function stb_textedit_find_charpos(find, str, n, single_line)
     local z = STB_TEXTEDIT_STRINGLEN(str)
     local first
 
-    -- special case if it's at the end (may not be needed?)
     if n == z + 1 and single_line then
+        -- special case if it's at the end (may not be needed?)
         STB_TEXTEDIT_LAYOUTROW(r, str, 1)
         find.y = 0
         find.first_char = 1
@@ -420,18 +674,18 @@ function stb_textedit_find_charpos(find, str, n, single_line)
         if n < i + r.num_chars - 1 then
             break
         end
-        if str.LastMoveDirectionLR == ImGuiDir.Right and str.Stb.cursor > 1 and str.Stb.cursor == i + r.num_chars and STB_TEXTEDIT_GETCHAR(str, i + r.num_chars - 1) ~= STB_TEXTEDIT_NEWLINE then -- [IMGUI] Wrapping point handling
+        if str.LastMoveDirectionLR == ImGuiDir.Right and str.Stb.cursor > 1 and str.Stb.cursor == i + r.num_chars and STB_TEXTEDIT_GETCHAR(str, i + r.num_chars - 1) ~= STB_TEXTEDIT_NEWLINE then -- [DEAR IMGUI] Wrapping point handling
             break
         end
-        if (i - 1) + r.num_chars == z and z > 0 and STB_TEXTEDIT_GETCHAR(str, z) ~= STB_TEXTEDIT_NEWLINE then -- [IMGUI] special handling for last line
+        if (i - 1) + r.num_chars == z and z > 0 and STB_TEXTEDIT_GETCHAR(str, z) ~= STB_TEXTEDIT_NEWLINE then -- [DEAR IMGUI] special handling for last line
-            break
+            break -- [DEAR IMGUI]
         end
         prev_start = i
         i = i + r.num_chars
         find.y = find.y + r.baseline_y_delta
-        if i == z + 1 then -- [IMGUI]
+        if i == z + 1 then -- [DEAR IMGUI]
-            r.num_chars = 0
+            r.num_chars = 0 -- [DEAR IMGUI]
-            break
+            break -- [DEAR IMGUI]
         end
     end
 
@@ -479,7 +733,7 @@ local function stb_textedit_delete(str, state, where, len)
     state.has_preferred_x = false
 end
 
--- delete the selection
+-- delete the section
 --- @param str   IMSTB_TEXTEDIT_STRING
 --- @param state STB_TexteditState
 local function stb_textedit_delete_selection(str, state)
@@ -498,7 +752,7 @@ local function stb_textedit_delete_selection(str, state)
     end
 end
 
--- canonicalize the selection so start <= end
+-- canoncialize the selection so start <= end
 --- @param state STB_TexteditState
 local function stb_textedit_sortselection(state)
     if state.select_end < state.select_start then
@@ -579,7 +833,7 @@ local function stb_textedit_paste_internal(str, state, text, len)
 end
 
 -- API key: process text input
--- [IMGUI] Added stb_textedit_text(), extracted out and called by stb_textedit_key() for backward compatibility.
+-- [DEAR IMGUI] Added stb_textedit_text(), extracted out and called by stb_textedit_key() for backward compatibility.
 --- @param str       IMSTB_TEXTEDIT_STRING
 --- @param state     STB_TexteditState
 --- @param text      IMSTB_TEXTEDIT_CHARTYPE[]
@@ -732,7 +986,7 @@ function stb_textedit_key(str, state, key)
                 break
             end
 
-            -- [IMGUI]
+            -- [DEAR IMGUI]
             -- going down while being on the last line shouldn't bring us to that line end
             --if STB_TEXTEDIT_GETCHAR(str, find.first_char + find.length - 1) ~= STB_TEXTEDIT_NEWLINE then
             --   break
@@ -929,8 +1183,8 @@ end
 -----------------------------------------------------
 ---
 --- Undo processing
---- OPTIMIZE: the undo/redo buffer should be circular
 ---
+--- @OPTIMIZE: the undo/redo buffer should be circular
 
 --- @param state StbUndoState
 local function stb_textedit_flush_redo(state)
@@ -950,7 +1204,7 @@ local function stb_textedit_discard_undo(state)
             IMSTB_TEXTEDIT_memmove(state.undo_char, 1, state.undo_char, n + 1, state.undo_char_point - 1)
             for i = 1, state.undo_point do
                 if state.undo_rec[i].char_storage >= 0 then
-                    state.undo_rec[i].char_storage = state.undo_rec[i].char_storage - n -- OPTIMIZE: get rid of char_storage and infer it
+                    state.undo_rec[i].char_storage = state.undo_rec[i].char_storage - n -- @OPTIMIZE: get rid of char_storage and infer it
                 end
             end
         end
@@ -983,7 +1237,7 @@ local function stb_textedit_discard_redo(state)
         end
 
         -- now move all the redo records towards the end of the buffer; the first one is at 'redo_point'
-        -- [IMGUI]
+        -- [DEAR IMGUI]
         local move_size = IMSTB_TEXTEDIT_UNDOSTATECOUNT - state.redo_point - 1
         IMSTB_TEXTEDIT_memmove(state.undo_rec, state.redo_point + 1, state.undo_rec, state.redo_point, move_size)
 
@@ -1129,6 +1383,9 @@ function stb_text_redo(str, state)
     local u = s.undo_rec[s.undo_point]
     local r = s.undo_rec[s.redo_point]
 
+    -- we KNOW there must be room for the undo record, because the redo record
+    -- was derived from an undo record
+
     u.delete_length = r.insert_length
     u.insert_length = r.delete_length
     u.where = r.where
@@ -1137,6 +1394,7 @@ function stb_text_redo(str, state)
     if r.delete_length > 0 then
         -- the redo record requires us to delete characters, so the undo record
         -- needs to store the characters
+
         if s.undo_char_point + u.insert_length > s.redo_char_point then
             u.insert_length = 0
             u.delete_length = 0
@@ -1144,6 +1402,7 @@ function stb_text_redo(str, state)
             u.char_storage = s.undo_char_point
             s.undo_char_point = s.undo_char_point + u.insert_length
 
+            -- now save the characters
             for i = 0, u.insert_length - 1 do
                 s.undo_char[u.char_storage + i] = STB_TEXTEDIT_GETCHAR(str, u.where + i)
             end
@@ -1153,6 +1412,7 @@ function stb_text_redo(str, state)
     end
 
     if r.insert_length ~= 0 then
+        -- easy case: need to insert n characters
         r.insert_length = STB_TEXTEDIT_INSERTCHARS(str, r.where, s.undo_char, r.char_storage, r.insert_length)
         s.redo_char_point = s.redo_char_point + r.insert_length
     end
@@ -1199,6 +1459,7 @@ function stb_text_makeundo_replace(str, state, where, old_length, new_length)
     end
 end
 
+-- reset the state to default
 --- @param state          STB_TexteditState
 --- @param is_single_line bool
 local function stb_textedit_clear_state(state, is_single_line)
@@ -1222,7 +1483,7 @@ return {
     click = stb_textedit_click,
     drag = stb_textedit_drag,
     createundo = stb_text_createundo,
-    initialize_state = stb_textedit_clear_state,
+    initialize_state = stb_textedit_clear_state, -- API initialize
 
     text = stb_textedit_text,
     key = stb_textedit_key,
@@ -1236,3 +1497,43 @@ return {
 
     HAS_SELECTION = STB_TEXT_HAS_SELECTION
 }
+
+-------------------------------------------------------------------------------
+-- This software is available under 2 licenses -- choose whichever you prefer.
+-------------------------------------------------------------------------------
+-- ALTERNATIVE A - MIT License
+-- Copyright (c) 2017 Sean Barrett
+-- Permission is hereby granted, free of charge, to any person obtaining a copy of
+-- this software and associated documentation files (the "Software"), to deal in
+-- the Software without restriction, including without limitation the rights to
+-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+-- of the Software, and to permit persons to whom the Software is furnished to do
+-- so, subject to the following conditions:
+-- The above copyright notice and this permission notice shall be included in all
+-- copies or substantial portions of the Software.
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+-- SOFTWARE.
+-------------------------------------------------------------------------------
+-- ALTERNATIVE B - Public Domain (www.unlicense.org)
+-- This is free and unencumbered software released into the public domain.
+-- Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+-- software, either in source code form or as a compiled binary, for any purpose,
+-- commercial or non-commercial, and by any means.
+-- In jurisdictions that recognize copyright laws, the author or authors of this
+-- software dedicate any and all copyright interest in the software to the public
+-- domain. We make this dedication for the benefit of the public at large and to
+-- the detriment of our heirs and successors. We intend this dedication to be an
+-- overt act of relinquishment in perpetuity of all present and future rights to
+-- this software under copyright law.
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+-- ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+-- WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+-------------------------------------------------------------------------------

imstb_truetype.lua

@@ -1,6 +1,164 @@
 --- Dear ImGui
 -- This is a Lua port of original `imstb_truetype.h`
 
+-- [DEAR IMGUI]
+-- This is a slightly modified version of stb_truetype.h 1.26.
+-- Mostly fixing for compiler and static analyzer warnings.
+-- Grep for [DEAR IMGUI] to find the changes.
+
+-- stb_truetype.h - v1.26 - public domain
+-- authored from 2009-2021 by Sean Barrett / RAD Game Tools
+--
+-- =======================================================================
+--
+--    NO SECURITY GUARANTEE -- DO NOT USE THIS ON UNTRUSTED FONT FILES
+--
+-- This library does no range checking of the offsets found in the file,
+-- meaning an attacker can use it to read arbitrary memory.
+--
+-- =======================================================================
+--
+--   This library processes TrueType files:
+--        parse files
+--        extract glyph metrics
+--        extract glyph shapes
+--        render glyphs to one-channel bitmaps with antialiasing (box filter)
+--
+--   Todo:
+--        non-MS cmaps
+--        crashproof on bad data
+--        hinting? (no longer patented)
+--        cleartype-style AA?
+--        optimize: build edge-list directly from curves
+--        optimize: rasterize directly from curves?
+--
+-- ADDITIONAL CONTRIBUTORS
+--
+--   Mikko Mononen: compound shape support, more cmap formats
+--   Tor Andersson: kerning, subpixel rendering
+--   Dougall Johnson: OpenType / Type 2 font handling
+--   Daniel Ribeiro Maciel: basic GPOS-based kerning
+--
+--   Misc other:
+--       Ryan Gordon
+--       Simon Glass
+--       github:IntellectualKitty
+--       Imanol Celaya
+--       Daniel Ribeiro Maciel
+--
+--   Bug/warning reports/fixes:
+--       "Zer" on mollyrocket       Fabian "ryg" Giesen   github:NiLuJe
+--       Cass Everitt               Martins Mozeiko       github:aloucks
+--       stoiko (Haemimont Games)   Cap Petschulat        github:oyvindjam
+--       Brian Hook                 Omar Cornut           github:vassvik
+--       Walter van Niftrik         Ryan Griege
+--       David Gow                  Peter LaValle
+--       David Given                Sergey Popov
+--       Ivan-Assen Ivanov          Giumo X. Clanjor
+--       Anthony Pesch              Higor Euripedes
+--       Johan Duparc               Thomas Fields
+--       Hou Qiming                 Derek Vinyard
+--       Rob Loach                  Cort Stratton
+--       Kenney Phillis Jr.         Brian Costabile
+--       Ken Voskuil (kaesve)
+--
+-- USAGE
+--
+--   "Load" a font file from a memory buffer (you have to keep the buffer loaded)
+--           stbtt_InitFont()
+--           stbtt_GetFontOffsetForIndex()        -- indexing for TTC font collections
+--
+--   Character advance/positioning
+--           stbtt_GetFontVMetrics()
+--
+--   Starting with version 1.06, the rasterizer was replaced with a new,
+--   faster and generally-more-precise rasterizer. The new rasterizer more
+--   accurately measures pixel coverage for anti-aliasing, except in the case
+--   where multiple shapes overlap, in which case it overestimates the AA pixel
+--   coverage. Thus, anti-aliasing of intersecting shapes may look wrong.
+--   (This port only implements the new rasterizer.)
+--
+-- ADDITIONAL DOCUMENTATION
+--
+--   Some important concepts to understand to use this library:
+--
+--      Codepoint
+--         Characters are defined by unicode codepoints, e.g. 65 is
+--         uppercase A, 231 is lowercase c with a cedilla, 0x7e30 is
+--         the hiragana for "ma".
+--
+--      Glyph
+--         A visual character shape (every codepoint is rendered as
+--         some glyph)
+--
+--      Glyph index
+--         A font-specific integer ID representing a glyph
+--
+--      Baseline
+--         Glyph shapes are defined relative to a baseline, which is the
+--         bottom of uppercase characters. Characters extend both above
+--         and below the baseline.
+--
+--      Current Point
+--         As you draw text to the screen, you keep track of a "current point"
+--         which is the origin of each character. The current point's vertical
+--         position is the baseline. Even "baked fonts" use this model.
+--
+--      Vertical Font Metrics
+--         The vertical qualities of the font, used to vertically position
+--         and space the characters. See docs for stbtt_GetFontVMetrics.
+--
+--      Font Size in Pixels or Points
+--         The preferred interface for specifying font sizes in stb_truetype
+--         is to specify how tall the font's vertical extent should be in pixels.
+--
+-- DETAILED USAGE:
+--
+--  Scale:
+--    Select how high you want the font to be, in pixels.
+--    Call ScaleForPixelHeight to compute a scale factor SF that will be
+--    used by all other functions.
+--
+--  Current point:
+--    Set the current point where the first character will appear. The
+--    first character could extend left of the current point; this is font
+--    dependent. You can either choose a current point that is the leftmost
+--    point and hope, or add some padding, or check the bounding box or
+--    left-side-bearing of the first character to be displayed and set
+--    the current point based on that.
+--
+--  Displaying a character:
+--    Compute the bounding box of the character. It will contain signed values
+--    relative to <current_point, baseline>. I.e. if it returns x0,y0,x1,y1,
+--    then the character should be displayed in the rectangle from
+--    <current_point+SF*x0, baseline+SF*y0> to <current_point+SF*x1,baseline+SF*y1).
+--
+--  Advancing for the next character:
+--    Call GlyphHMetrics, and compute 'current_point += SF * advance'.
+--
+--
+-- ADVANCED USAGE
+--
+--   Quality:
+--
+--    - Use the functions with Subpixel at the end to allow your characters
+--      to have subpixel positioning. Since the font is anti-aliased, not
+--      hinted, this is very import for quality. (This is not possible with
+--      baked fonts.)
+--
+--   Performance:
+--
+--    - Convert Unicode codepoints to glyph indexes and operate on the glyphs;
+--      if you don't do this, stb_truetype is forced to do the conversion on
+--      every call.
+--
+-- NOTES
+--
+--   The system uses the raw data found in the .ttf file without changing it
+--   and without building auxiliary data structures. This is a bit inefficient
+--   on little-endian systems (the data is big-endian), but assuming you're
+--   caching the bitmaps or glyph shapes this shouldn't be a big deal.
+
 --- STBTT_RASTERIZER_VERSION == 2
 
 local stbtt_fontinfo
@@ -21,7 +179,7 @@ local stbtt_FindGlyphIndex
 local STBTT_MAX_OVERSAMPLE = 8
 
 --- @enum STBTT_PLATFORM_ID
-local STBTT_PLATFORM_ID = {
+local STBTT_PLATFORM_ID = { -- platformID
     UNICODE   = 0,
     MAC       = 1,
     ISO       = 2,
@@ -29,7 +187,7 @@ local STBTT_PLATFORM_ID = {
 }
 
 --- @enum STBTT_MS_EID
-local STBTT_MS_EID = {
+local STBTT_MS_EID = { -- encodingID for STBTT_PLATFORM_ID_MICROSOFT
     SYMBOL       = 0,
     UNICODE_BMP  = 1,
     SHIFTJIS     = 2,
@@ -75,6 +233,7 @@ local stbtt_int8    = ImS8
 local stbtt_uint8   = ImU8
 local unsigned_char = stbtt_uint8
 
+-- private structure
 --- @class stbtt__buf
 --- @field data?  table # 1-based byte table
 --- @field offset int   # Every access to `data` will be offset by this
@@ -93,6 +252,8 @@ local function stbtt__buf(initial_offset)
     }
 end
 
+-- The following structure is defined publicly so you can declare one on
+-- the stack or as a global or etc, but you should treat it as opaque.
 --- @class stbtt_fontinfo
 --- @field userdata         any
 --- @field data             table       # pointer to .ttf file
@@ -283,6 +444,7 @@ local function stbtt__new_active(e, off_x, start_point)
     return z
 end
 
+-- @TODO: don't expose this structure
 --- @class stbtt__bitmap
 --- @field w      int
 --- @field h      int
@@ -496,7 +658,7 @@ end
 -------------------------------------
 -------------------------------------
 ---
---- Accessors to parse data from file
+--- accessors to parse data from file
 ---
 ---
 
@@ -535,14 +697,16 @@ local function stbtt_tag4(p, c0, c1, c2, c3, offset) offset = offset or 0; retur
 local function stbtt_tag(p, str, offset) local c0, c1, c2, c3 = string.byte(str, 1, 4); return stbtt_tag4(p, c0, c1, c2, c3, offset) end
 
 local function stbtt__isfont(font)
-    if stbtt_tag4(font, 49, 0, 0, 0) then return true end
+    -- check the version number
-    if stbtt_tag(font, "typ1") then return true end
+    if stbtt_tag4(font, 49, 0, 0, 0) then return true end -- TrueType 1
-    if stbtt_tag(font, "OTTO") then return true end
+    if stbtt_tag(font, "typ1") then return true end -- TrueType with type 1 font -- we don't support this!
-    if stbtt_tag4(font, 0, 1, 0, 0) then return true end
+    if stbtt_tag(font, "OTTO") then return true end -- OpenType with CFF
-    if stbtt_tag(font, "true") then return true end
+    if stbtt_tag4(font, 0, 1, 0, 0) then return true end -- OpenType 1.0
+    if stbtt_tag(font, "true") then return true end -- Apple specification for TrueType fonts
     return false
 end
 
+-- @OPTIMIZE: binary search
 local function stbtt__find_table(data, font_start, tag)
     local num_tables = ttUSHORT(data, font_start + 4)
     local tabledir = font_start + 12
@@ -556,11 +720,14 @@ local function stbtt__find_table(data, font_start, tag)
 end
 
 local function stbtt_GetFontOffsetForIndex_internal(font_collection, index)
+    -- if it's just a font, there's only one valid index
     if stbtt__isfont(font_collection) then
         if index == 0 then return 0 else return -1 end
     end
 
+    -- check if it's a TTC
     if stbtt_tag(font_collection, "ttcf") then
+        -- version 1?
         if ttULONG(font_collection, 4) == 0x00010000 or ttULONG(font_collection, 4) == 0x00020000 then
             local n = ttLONG(font_collection, 8)
             if index >= n then
@@ -598,23 +765,25 @@ local function stbtt_InitFont_internal(info, data, fontstart)
     info.fontstart = fontstart
     info.cff = stbtt__new_buf(nil, 0)
 
-    cmap = stbtt__find_table(data, fontstart, "cmap")
+    cmap = stbtt__find_table(data, fontstart, "cmap")      -- required
-    info.loca = stbtt__find_table(data, fontstart, "loca")
+    info.loca = stbtt__find_table(data, fontstart, "loca") -- required
-    info.head = stbtt__find_table(data, fontstart, "head")
+    info.head = stbtt__find_table(data, fontstart, "head") -- required
-    info.glyf = stbtt__find_table(data, fontstart, "glyf")
+    info.glyf = stbtt__find_table(data, fontstart, "glyf") -- required
-    info.hhea = stbtt__find_table(data, fontstart, "hhea")
+    info.hhea = stbtt__find_table(data, fontstart, "hhea") -- required
-    info.hmtx = stbtt__find_table(data, fontstart, "hmtx")
+    info.hmtx = stbtt__find_table(data, fontstart, "hmtx") -- required
-    info.kern = stbtt__find_table(data, fontstart, "kern")
+    info.kern = stbtt__find_table(data, fontstart, "kern") -- not required
-    info.gpos = stbtt__find_table(data, fontstart, "GPOS")
+    info.gpos = stbtt__find_table(data, fontstart, "GPOS") -- not required
 
     if (cmap == 0 or info.head == 0 or info.hhea == 0 or info.hmtx == 0) then
         return false
     end
     if info.glyf ~= 0 then
+        -- required for truetype
         if info.loca == 0 then
             return false
         end
     else
+        -- initialization for CFF / Type2 fonts (OTF)
         local cff = stbtt__find_table(data, fontstart, "CFF ")
         if cff == 0 then
             return false
@@ -623,14 +792,16 @@ local function stbtt_InitFont_internal(info, data, fontstart)
         info.fontdicts = stbtt__new_buf(nil, 0)
         info.fdselect = stbtt__new_buf(nil, 0)
 
-        info.cff = stbtt__new_buf(data, 64 * 1024 * 1024, cff) -- TODO: this should use size from table
+        -- @TODO this should use size from table (not 512MB)
+        info.cff = stbtt__new_buf(data, 64 * 1024 * 1024, cff) -- PORT: 64MB here instead of 512MB
         local b = info.cff
 
         -- read the header
         stbtt__buf_skip(b, 2)
-        stbtt__buf_seek(b, stbtt__buf_get8(b))
+        stbtt__buf_seek(b, stbtt__buf_get8(b)) -- hdrsize
 
-        -- TODO: the name INDEX could list multiple fonts, but we just use the first one.
+        -- @TODO the name INDEX could list multiple fonts,
+        -- but we just use the first one.
         stbtt__cff_get_index(b) -- name INDEX
         local topdictidx = stbtt__cff_get_index(b)
         local topdict = stbtt__cff_index_get(topdictidx, 0)
@@ -643,6 +814,7 @@ local function stbtt_InitFont_internal(info, data, fontstart)
         local fdselectoff = stbtt__dict_get_ints(topdict, bit32.bor(0x100, 37), 1)
         info.subrs = stbtt__get_subrs(b, topdict)
 
+        -- we only support Type 2 charstrings
         if cstype[1] ~= 2 then
             return false
         end
@@ -651,6 +823,7 @@ local function stbtt_InitFont_internal(info, data, fontstart)
         end
 
         if fdarrayoff[1] ~= 0 then
+            -- looks like a CID font
             if fdselectoff[1] == 0 then
                 return false
             end
@@ -673,19 +846,26 @@ local function stbtt_InitFont_internal(info, data, fontstart)
 
     info.svg = -1
 
+    -- find a cmap encoding table we understand *now* to avoid searching
+    -- later. (todo: could make this installable)
+    -- the same regardless of glyph.
     numTables = ttUSHORT(data, cmap + 2)
     info.index_map = 0
     for i = 0, numTables - 1 do
         local encoding_record = cmap + 4 + 8 * i
+        -- find an encoding we understand:
         local platform_id = ttUSHORT(data, encoding_record)
 
         if platform_id == STBTT_PLATFORM_ID.MICROSOFT then
             local ms_eid = ttUSHORT(data, encoding_record + 2)
 
             if ms_eid == STBTT_MS_EID.UNICODE_BMP or ms_eid == STBTT_MS_EID.UNICODE_FULL then
+                -- MS/Unicode
                 info.index_map = cmap + ttULONG(data, encoding_record + 4)
             end
         elseif platform_id == STBTT_PLATFORM_ID.UNICODE then
+            -- Mac/iOS has these
+            -- all the encodingIDs are unicode, so we don't bother to check it
             info.index_map = cmap + ttULONG(data, encoding_record + 4)
         end
     end
@@ -697,6 +877,11 @@ local function stbtt_InitFont_internal(info, data, fontstart)
     return true
 end
 
+-- If you're going to perform multiple operations on the same character
+-- and you want a speed-up, call this function with the character you're
+-- going to process, then use glyph-based functions instead of the
+-- codepoint-based functions.
+-- Returns 0 if the character codepoint is not defined in the font.
 --- @param info              stbtt_fontinfo
 --- @param unicode_codepoint int
 function stbtt_FindGlyphIndex(info, unicode_codepoint)
@@ -704,7 +889,7 @@ function stbtt_FindGlyphIndex(info, unicode_codepoint)
     local index_map = info.index_map
 
     local format = ttUSHORT(data, index_map + 0)
-    if format == 0 then
+    if format == 0 then -- apple byte encoding
         local bytes = ttUSHORT(data, index_map + 2)
         if unicode_codepoint < bytes - 6 then
             return ttBYTE(data, index_map + 6 + unicode_codepoint)
@@ -718,14 +903,15 @@ function stbtt_FindGlyphIndex(info, unicode_codepoint)
         end
         return 0
     elseif format == 2 then
-        STBTT_assert(false) -- TODO: high-byte mapping for japanese/chinese/korean
+        STBTT_assert(false) -- @TODO: high-byte mapping for japanese/chinese/korean
         return 0
-    elseif format == 4 then
+    elseif format == 4 then -- standard mapping for windows fonts: binary search collection of ranges
         local segcount = bit32.rshift(ttUSHORT(data, index_map + 6), 1)
         local searchRange = bit32.rshift(ttUSHORT(data, index_map + 8), 1)
         local entrySelector = ttUSHORT(data, index_map + 10)
         local rangeShift = bit32.rshift(ttUSHORT(data, index_map + 12), 1)
 
+        -- do a binary search of the segments
         local endCount = index_map + 14
         local search = endCount
 
@@ -733,10 +919,13 @@ function stbtt_FindGlyphIndex(info, unicode_codepoint)
             return 0
         end
 
+        -- they lie from endCount .. endCount + segCount
+        -- but searchRange is the nearest power of two, so...
         if unicode_codepoint >= ttUSHORT(data, search + rangeShift * 2) then
             search = search + rangeShift * 2
         end
 
+        -- now decrement to bias correctly to find smallest
         search = search - 2
         while entrySelector ~= 0 do
             searchRange = bit32.rshift(searchRange, 1)
@@ -768,8 +957,9 @@ function stbtt_FindGlyphIndex(info, unicode_codepoint)
         local ngroups = ttULONG(data, index_map + 12)
         local low = 0
         local high = ngroups
+        -- Binary search the right group.
         while low < high do
-            local mid = low + bit32.rshift(high - low, 1)
+            local mid = low + bit32.rshift(high - low, 1) -- rounds down, so low <= mid < high
             local start_char = ttULONG(data, index_map + 16 + mid * 12)
             local end_char = ttULONG(data, index_map + 16 + mid * 12 + 4)
             if unicode_codepoint < start_char then
@@ -785,10 +975,10 @@ function stbtt_FindGlyphIndex(info, unicode_codepoint)
                 end
             end
         end
-        return 0
+        return 0 -- not found
     end
 
-    -- TODO:
+    -- @TODO
     STBTT_assert(false)
     return 0
 end
@@ -810,8 +1000,8 @@ end
 local function stbtt__GetGlyfOffset(info, glyph_index)
     STBTT_assert(info.cff.size == 0)
 
-    if glyph_index >= info.numGlyphs then return -1 end
+    if glyph_index >= info.numGlyphs then return -1 end -- glyph index out of range
-    if info.indexToLocFormat >= 2 then return -1 end
+    if info.indexToLocFormat >= 2 then return -1 end -- unknown index->glyph map format
 
     local g1, g2
     if info.indexToLocFormat == 0 then
@@ -822,9 +1012,10 @@ local function stbtt__GetGlyfOffset(info, glyph_index)
         g2 = info.glyf + ttULONG(info.data, info.loca + glyph_index * 4 + 4)
     end
 
-    if g1 == g2 then return -1 else return g1 end
+    if g1 == g2 then return -1 else return g1 end -- if length is 0, return -1
 end
 
+-- Gets the bounding box of the visible part of the glyph, in unscaled coordinates
 --- @return integer, integer?, integer?, integer?, integer?
 local function stbtt_GetGlyphBox(info, glyph_index)
     local n, x0, y0, x1, y1
@@ -896,7 +1087,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
         local points = (endPtsOfContours + numberOfContours * 2 + 2 + ins) + 1 -- 1-based idx
 
         local n = 1 + ttUSHORT(data, endPtsOfContours + numberOfContours * 2 - 2)
-        local m = n + 2 * numberOfContours
+        local m = n + 2 * numberOfContours -- a loose bound on how many vertices we might need
 
         vertices = {}
         for i = 1, m do vertices[i] = stbtt_vertex() end
@@ -907,7 +1098,11 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
         local next_move = 0
         local flagcount = 0
 
-        local off = m - n
+        -- in first pass, we load uninterpreted data into the allocated array
+        -- above, shifted to the end of the array so we won't overwrite it when
+        -- we create our final data starting from the front
+
+        local off = m - n -- starting offset for uninterpreted data, regardless of how m ends up being calculated
 
         -- first load flags
         local flags = 0
@@ -934,7 +1129,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
             if bit32.band(flags, 2) ~= 0 then
                 local dx = data[points]
                 points = points + 1
-                if bit32.band(flags, 16) ~= 0 then
+                if bit32.band(flags, 16) ~= 0 then -- ???
                     x = x + dx
                 else
                     x = x - dx
@@ -956,7 +1151,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
             if bit32.band(flags, 4) ~= 0 then
                 local dy = data[points]
                 points = points + 1
-                if bit32.band(flags, 32) ~= 0 then
+                if bit32.band(flags, 32) ~= 0 then -- ???
                     y = y + dy
                 else
                     y = y - dy
@@ -987,15 +1182,19 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                 -- now start the new one
                 start_off = (bit32.band(flags, 1) == 0)
                 if start_off then
+                    -- if we start off with an off-curve point, then when we need to find a point on the curve
+                    -- where we can start, and we need to save some state for when we wraparound.
                     scx = x
                     scy = y
                     if bit32.band(vertices[off + i + 1].type, 1) == 0 then
+                        -- next point is also a curve point, so interpolate an on-point curve
                         sx = bit32.rshift(x + stbtt_int32(vertices[off + i + 1].x), 1)
                         sy = bit32.rshift(y + stbtt_int32(vertices[off + i + 1].y), 1)
                     else
+                        -- otherwise just use the next point as our start point
                         sx = stbtt_int32(vertices[off + i + 1].x)
                         sy = stbtt_int32(vertices[off + i + 1].y)
-                        i = i + 1
+                        i = i + 1 -- we're using point i+1 as the starting point, so skip it
                     end
                 else
                     sx = x
@@ -1007,8 +1206,8 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                 next_move = 1 + ttUSHORT(data, endPtsOfContours + j * 2)
                 j = j + 1
             else
-                if bit32.band(flags, 1) == 0 then
+                if bit32.band(flags, 1) == 0 then -- if it's a curve
-                    if was_off then
+                    if was_off then -- two off-curve control points in a row means interpolate an on-curve midpoint
                         stbtt_setvertex(vertices[num_vertices + 1], STBTT_VTX.CURVE, bit32.rshift(cx + x, 1), bit32.rshift(cy + y, 1), cx, cy)
                         num_vertices = num_vertices + 1
                     end
@@ -1032,6 +1231,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
 
         num_vertices = stbtt__close_shape(vertices, num_vertices, was_off, start_off, sx, sy, scx, scy, cx, cy)
     elseif numberOfContours < 0 then
+        -- Compound shapes.
         local more = 1
         local comp = g + 10
         num_vertices = 0
@@ -1047,8 +1247,8 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
             flags = ttSHORT(data, comp) comp = comp + 2
             gidx = ttSHORT(data, comp) comp = comp + 2
 
-            if bit32.band(flags, 2) ~= 0 then
+            if bit32.band(flags, 2) ~= 0 then -- XY values
-                if bit32.band(flags, 1) ~= 0 then
+                if bit32.band(flags, 1) ~= 0 then -- shorts
                     mtx[5] = ttSHORT(data, comp) comp = comp + 2
                     mtx[6] = ttSHORT(data, comp) comp = comp + 2
                 else
@@ -1056,7 +1256,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                     mtx[6] = ttCHAR(data, comp) comp = comp + 1
                 end
             else
-                -- TODO: handle matching point
+                -- @TODO handle matching point
                 STBTT_assert(false)
             end
 
@@ -1083,11 +1283,14 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                 mtx[4] = ttSHORT(data, comp) / 16384.0 comp = comp + 2
             end
 
+            -- Find transformation scales.
             m = STBTT_sqrt(mtx[1] * mtx[1] + mtx[2] * mtx[2])
             n = STBTT_sqrt(mtx[3] * mtx[3] + mtx[4] * mtx[4])
 
+            -- Get indexed glyph.
             comp_num_vertices, comp_verts = stbtt_GetGlyphShape(info, gidx)
             if comp_num_vertices > 0 then
+                -- Transform vertices.
                 for i = 1, comp_num_vertices do
                     local v = comp_verts[i]
                     local x = v.x
@@ -1100,6 +1303,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                     v.cy = stbtt_int16(n * (mtx[2] * x + mtx[4] * y + mtx[6]))
                 end
 
+                -- Append vertices.
                 if num_vertices == 0 then -- LUA: No malloc
                     vertices = comp_verts
                 else
@@ -1111,6 +1315,7 @@ local function stbtt__GetGlyphShapeTT(info, glyph_index)
                 num_vertices = num_vertices + comp_num_vertices
             end
 
+            -- More components ?
             more = bit32.band(flags, bit32.lshift(1, 5))
         end
     end
@@ -1266,7 +1471,7 @@ local function stbtt__run_charstring(info, glyph_index, c)
         clear_stack = 1
         b0 = stbtt__buf_get8(b)
 
-        -- TODO: implement hinting
+        -- @TODO implement hinting
         if b0 == 0x13 or b0 == 0x14 then -- hintmask or cntrmask
             if in_header then
                 maskbits = maskbits + trunc(sp / 2)  -- implicit "vstem"
@@ -1415,6 +1620,8 @@ local function stbtt__run_charstring(info, glyph_index, c)
         elseif b0 == 0x0C then -- two-byte escape
             local b1 = stbtt__buf_get8(b)
 
+            -- @TODO These "flex" implementations ignore the flex-depth and resolution,
+            -- and always draw beziers.
             if b1 == 0x22 then -- hflex
                 if sp < 7 then return STBTT__CSERR("hflex stack") end
                 local dx1 = s[0]
@@ -1547,6 +1754,15 @@ function stbtt__GetGlyphInfoT2(info, glyph_index)
     return ((r ~= 0) and c.num_vertices or 0), x0, y0, x1, y1
 end
 
+-- returns # of vertices and fills *vertices with the pointer to them
+--   these are expressed in "unscaled" coordinates
+--
+-- The shape is a series of contours. Each one starts with
+-- a STBTT_moveto, then consists of a series of mixed
+-- STBTT_lineto and STBTT_curveto segments. A lineto
+-- draws a line from previous endpoint to its x,y; a curveto
+-- draws a quadratic bezier from previous endpoint to
+-- its x,y, using cx,cy as the bezier control point.
 --- @param info        stbtt_fontinfo
 --- @param glyph_index int
 function stbtt_GetGlyphShape(info, glyph_index)
@@ -1557,6 +1773,9 @@ function stbtt_GetGlyphShape(info, glyph_index)
     end
 end
 
+-- leftSideBearing is the offset from the current horizontal position to the left edge of the character
+-- advanceWidth is the offset from the current horizontal position to the next horizontal position
+--   these are expressed in unscaled coordinates
 --- @param info        stbtt_fontinfo
 --- @param glyph_index int
 function stbtt_GetGlyphHMetrics(info, glyph_index)
@@ -1574,6 +1793,12 @@ function stbtt_GetGlyphHMetrics(info, glyph_index)
     return advanceWidth, leftSideBearing
 end
 
+-- ascent is the coordinate above the baseline the font extends; descent
+-- is the coordinate below the baseline the font extends (i.e. it is typically negative)
+-- lineGap is the spacing between one row's descent and the next row's ascent...
+-- so you should advance the vertical position by "ascent - descent + lineGap"
+--   these are expressed in unscaled coordinates, so you must multiply by
+--   the scale factor for a given size
 --- @param info stbtt_fontinfo
 function stbtt_GetFontVMetrics(info)
     local ascent = ttSHORT(info.data, info.hhea + 4)
@@ -1583,6 +1808,12 @@ function stbtt_GetFontVMetrics(info)
     return ascent, descent, lineGap
 end
 
+-- computes a scale factor to produce a font whose "height" is 'pixels' tall.
+-- Height is measured as the distance from the highest ascender to the lowest
+-- descender; in other words, it's equivalent to calling stbtt_GetFontVMetrics
+-- and computing:
+--       scale = pixels / (ascent - descent)
+-- so if you prefer to measure height by the ascent only, use a similar calculation.
 --- @param info   stbtt_fontinfo
 --- @param height float
 function stbtt_ScaleForPixelHeight(info, height)
@@ -1593,10 +1824,12 @@ end
 ------------------------------------
 ------------------------------------
 ---
---- Antialiasing software rasterizer
+--- antialiasing software rasterizer
 ---
 ---
 
+-- same as stbtt_GetGlyphBitmapBox, but you can specify a subpixel
+-- shift for the character
 --- @param font    stbtt_fontinfo
 --- @param glyph   int
 --- @param scale_x float
@@ -1624,6 +1857,11 @@ function stbtt_GetGlyphBitmapBoxSubpixel(font, glyph, scale_x, scale_y, shift_x,
     return ix0, iy0, ix1, iy1
 end
 
+-- get the bbox of the bitmap centered around the glyph origin; so the
+-- bitmap width is ix1-ix0, height is iy1-iy0, and location to place
+-- the bitmap top left is (leftSideBearing*scale,iy0).
+-- (Note that the bitmap uses y-increases-down, but the shape uses
+-- y-increases-up, so GlyphBitmapBox and GlyphBox are inverted.)
 --- @param font    stbtt_fontinfo
 --- @param glyph   int
 --- @param scale_x float
@@ -1646,6 +1884,8 @@ end
 ---     stbtt_MakeGlyphBitmap
 ---     stbtt_GetGlyphBitmapSubpixel
 
+-- the edge passed in here does not cross the vertical line at x or the vertical line at x+1
+-- (i.e. it has already been clipped to those)
 --- @param scanline float[]
 --- @param x        int
 --- @param e        stbtt__active_edge
@@ -1687,7 +1927,7 @@ local function stbtt__handle_clipped_edge(scanline, x, e, x0, y0, x1, y1)
         -- do nothing
     else
         STBTT_assert(x0 >= x and x0 <= x + 1 and x1 >= x and x1 <= x + 1)
-        scanline[x] = scanline[x] + e.direction * (y1 - y0) * (1 - ((x0 - x) + (x1 - x)) / 2)
+        scanline[x] = scanline[x] + e.direction * (y1 - y0) * (1 - ((x0 - x) + (x1 - x)) / 2) -- coverage = 1 - average x position
     end
 end
 
@@ -1725,6 +1965,7 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
 
     while e do
         -- brute force every pixel
+
         -- compute intersection points with top & bottom
         STBTT_assert(e.ey >= y_top)
 
@@ -1768,8 +2009,8 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
             if x_top >= 0 and x_bottom >= 0 and x_top < len and x_bottom < len then
                 -- from here on, we don't have to range check x values
                 if trunc(x_top) == trunc(x_bottom) then
-                    -- simple case, only spans one pixel
                     local height
+                    -- simple case, only spans one pixel
                     local x = trunc(x_top)
                     height = (sy1 - sy0) * e.direction
                     STBTT_assert(x >= 0 and x < len)
@@ -1801,8 +2042,25 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
                     -- compute intersection with y axis at x2
                     y_final = y_top + dy * (x2 - x0)
 
+                    --           x1    x_top                            x2    x_bottom
+                    --     y_top  +------|-----+------------+------------+--------|---+------------+
+                    --            |            |            |            |            |            |
+                    --            |            |            |            |            |            |
+                    --       sy0  |      Txxxxx|............|............|............|............|
+                    -- y_crossing |            *xxxxx.......|............|............|............|
+                    --            |            |     xxxxx..|............|............|............|
+                    --            |            |     /-   xx*xxxx........|............|............|
+                    --            |            | dy <       |    xxxxxx..|............|............|
+                    --   y_final  |            |     \-     |          xx*xxx.........|............|
+                    --       sy1  |            |            |            |   xxxxxB...|............|
+                    --            |            |            |            |            |            |
+                    --            |            |            |            |            |            |
+                    --  y_bottom  +------------+------------+------------+------------+------------+
+                    --
+                    -- goal is to measure the area covered by '.' in each pixel
+
                     -- if x2 is right at the right edge of x1, y_crossing can blow up, github #1057
-                    -- TODO: maybe test against sy1 rather than y_bottom?
+                    -- @TODO: maybe test against sy1 rather than y_bottom?
                     if y_crossing > y_bottom then
                         y_crossing = y_bottom
                     end
@@ -1824,6 +2082,16 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
                         end
                     end
 
+                    -- in second pixel, area covered by line segment found in first pixel
+                    -- is always a rectangle 1 wide * the height of that line segment; this
+                    -- is exactly what the variable 'area' stores. it also gets a contribution
+                    -- from the line segment within it. the THIRD pixel will get the first
+                    -- pixel's rectangle contribution, the second pixel's rectangle contribution,
+                    -- and its own contribution. the 'own contribution' is the same in every pixel except
+                    -- the leftmost and rightmost, a trapezoid that slides down in each pixel.
+                    -- the second pixel's contribution to the third pixel will be the
+                    -- rectangle 1 wide times the height change in the second pixel, which is dy.
+
                     step = sign * dy * 1 -- dy is dy/dx, change in y for every 1 change in x,
                     -- which multiplied by 1-pixel-width is how much pixel area changes for each step in x
                     -- so the area advances by 'step' every time
@@ -1843,7 +2111,27 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
                     scanline_fill[x2 + 1] = scanline_fill[x2 + 1] + sign * (sy1 - sy0)
                 end
             else
+                -- if edge goes outside of box we're drawing, we require
+                -- clipping logic. since this does not match the intended use
+                -- of this library, we use a different, very slow brute
+                -- force implementation
+                -- note though that this does happen some of the time because
+                -- x_top and x_bottom can be extrapolated at the top & bottom of
+                -- the shape and actually lie outside the bounding box
                 for x = 0, len - 1 do
+                    -- cases:
+                    --
+                    -- there can be up to two intersections with the pixel. any intersection
+                    -- with left or right edges can be handled by splitting into two (or three)
+                    -- regions. intersections with top & bottom do not necessitate case-wise logic.
+                    --
+                    -- the old way of doing this found the intersections with the left & right edges,
+                    -- then used some simple logic to produce up to three segments in sorted order
+                    -- from top-to-bottom. however, this had a problem: if an x edge was epsilon
+                    -- across the x border, then the corresponding y position might not be distinct
+                    -- from the other y segment, and it might ignored as an empty segment. to avoid
+                    -- that, we need to explicitly produce segments based on x positions.
+
                     -- rename variables to clearly-defined pairs
                     local y0 = y_top
                     local x1 = x
@@ -1887,6 +2175,7 @@ local function stbtt__fill_active_edges_new(scanline, scanline_fill, len, e, y_t
     end
 end
 
+-- directly AA rasterize edges w/o supersampling
 --- @param result     stbtt__bitmap
 --- @param e          stbtt__edge
 --- @param n          int
@@ -1914,28 +2203,33 @@ local function stbtt__rasterize_sorted_edges(result, e, n, vsubsample, off_x, of
         for i = 0, result.w - 1 do scanline[i] = 0 end
         for i = 0, result.w do scanline2[i] = 0 end
 
+        -- update all active edges;
+        -- remove all active edges that terminate before the top of this scanline
         local prev = nil
         local curr = active
         while curr do
             local next = curr.next
             if curr.ey <= scan_y_top then
-                if prev then prev.next = next
+                if prev then prev.next = next -- delete from list
                 else          active   = next end
                 curr.direction = 0
             else
-                prev = curr
+                prev = curr -- advance through list
             end
             curr = next
         end
 
+        -- insert all edges that start before the bottom of this scanline
         local edge = e[p]
         while edge.y0 <= scan_y_bottom do
             if edge.y0 ~= edge.y1 then
                 local z = stbtt__new_active(edge, off_x, scan_y_top)
                 if j == 0 and off_y ~= 0 and z.ey < scan_y_top then
+                    -- this can happen due to subpixel positioning and some kind of fp rounding error i think
                     z.ey = scan_y_top
                 end
-                STBTT_assert(z.ey >= scan_y_top)
+                STBTT_assert(z.ey >= scan_y_top) -- if we get really unlucky a tiny bit of an edge can be out of bounds
+                -- insert at front
                 z.next = active
                 active = z
             end
@@ -1943,6 +2237,7 @@ local function stbtt__rasterize_sorted_edges(result, e, n, vsubsample, off_x, of
             edge = e[p]
         end
 
+        -- now process all active edges
         if active then
             stbtt__fill_active_edges_new(scanline, scanline2, result.w, active, scan_y_top)
         end
@@ -1961,10 +2256,11 @@ local function stbtt__rasterize_sorted_edges(result, e, n, vsubsample, off_x, of
             end
         end
 
+        -- advance all the edges
         step = active
         while step do
-            step.fx = step.fx + step.fdx
+            step.fx = step.fx + step.fdx -- advance to position for current scanline
-            step = step.next
+            step = step.next -- advance through list
         end
 
         y = y + 1
@@ -1999,6 +2295,7 @@ end
 local function stbtt__rasterize(result, pts, wcount, windings, scale_x, scale_y, shift_x, shift_y, off_x, off_y, invert)
     local y_scale_inv = (invert) and -scale_y or scale_y
     local vsubsample = 1 -- STBTT_RASTERIZER_VERSION == 2
+    -- vsubsample should divide 255 evenly; otherwise we won't reach full opacity
 
     -- now we have to blow out the windings into explicit edge lists
     local n = 0
@@ -2066,8 +2363,7 @@ local function stbtt__add_point(points, n, x, y)
     points[n + 1].y = y
 end
 
--- tessellate until threshold p is happy...
+-- tessellate until threshold p is happy... @TODO warped to compensate for non-linear stretching
--- TODO: warped to compensate for non-linear stretching
 --- @param points?                   stbtt__point[]
 --- @param num_points                int
 --- @param x0                        float
@@ -2116,7 +2412,7 @@ end
 --- @param n                         int
 --- @return int num_points # updated num_points passed in
 local function stbtt__tesselate_cubic(points, num_points, x0, y0, x1, y1, x2, y2, x3, y3, objspace_flatness_squared, n)
-    -- TODO: this "flatness" calculation is just made-up nonsense that seems to work well enough
+    -- @TODO this "flatness" calculation is just made-up nonsense that seems to work well enough
     local dx0 = x1 - x0
     local dy0 = y1 - y0
     local dx1 = x2 - x1
@@ -2159,6 +2455,7 @@ local function stbtt__tesselate_cubic(points, num_points, x0, y0, x1, y1, x2, y2
     return num_points
 end
 
+-- returns number of contours
 --- @param vertices          stbtt_vertex[]
 --- @param num_verts         int
 --- @param objspace_flatness float
@@ -2235,6 +2532,7 @@ local function stbtt_FlattenCurves(vertices, num_verts, objspace_flatness)
     return points, num_contours, contour_lengths
 end
 
+-- rasterize a shape with quadratic beziers into a bitmap
 --- @param result             stbtt__bitmap
 --- @param flatness_in_pixels float
 --- @param vertices           stbtt_vertex[]
@@ -2258,6 +2556,11 @@ local function stbtt_Rasterize(result, flatness_in_pixels, vertices, num_verts,
     end
 end
 
+-- renders the glyph into storage you pass in for the bitmap,
+-- in the form of 'output', with row spacing of 'out_stride' bytes. the bitmap
+-- is clipped to out_w/out_h bytes. Call stbtt_GetGlyphBitmapBox to get the
+-- width and height and positioning info for it first. You can also specify
+-- a subpixel shift for the character.
 --- @param info       stbtt_fontinfo
 --- @param output     unsigned_char[]
 --- @param out_w      int
@@ -2286,7 +2589,7 @@ end
 -----------------
 -----------------
 ---
---- Bitmap baking
+--- bitmap baking
 ---
 ---
 
@@ -2298,7 +2601,7 @@ end
 ---------------------------
 ---------------------------
 ---
---- Bitmap baking / packing
+--- bitmap baking / packing
 ---
 ---
 
@@ -2380,9 +2683,16 @@ local function stbtt__oversample_shift(oversample)
     if oversample == 0 then
         return 0.0
     end
+
+    -- The prefilter is a box filter of width "oversample",
+    -- which shifts phase by (oversample - 1)/2 pixels in
+    -- oversampled space. We want to shift in the opposite
+    -- direction to counter this.
     return -(oversample - 1) / (2.0 * oversample)
 end
 
+-- same as stbtt_MakeGlyphBitmapSubpixel, but prefiltering
+-- is performed. Returns (sub_x, sub_y).
 --- @param info        stbtt_fontinfo
 --- @param output      unsigned_char[]
 --- @param out_w       int
@@ -2415,7 +2725,7 @@ end
 -------------------
 -------------------
 ---
---- SDF computation
+--- sdf computation
 ---
 ---
 
@@ -2441,10 +2751,20 @@ end
 ---     stbtt__matchpair
 ---     stbtt__matches
 
+-- Each .ttf/.ttc file may have more than one font. Each font has a sequential
+-- index number starting from 0. Call this function to get the font offset for
+-- a given index; it returns -1 if the index is out of range. A regular .ttf
+-- file will only define one font and it always be at offset 0, so it will
+-- return '0' for index 0, and -1 for all other indices.
 --- @param data  table
 --- @param index int
 function stbtt_GetFontOffsetForIndex(data, index) return stbtt_GetFontOffsetForIndex_internal(data, index) end
 
+-- Given an offset into the file that defines a font, this function builds
+-- the necessary cached info for the rest of the system. You must allocate
+-- the stbtt_fontinfo yourself (see stbtt_fontinfo()), and stbtt_InitFont will fill it out. You don't
+-- need to do anything special to free it, because the contents are pure
+-- value data with no additional data structures. Returns false on failure.
 --- @param info   stbtt_fontinfo
 --- @param data   table
 --- @param offset int

tools/minify.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+# Minifies a Lua/Luau file: drops comments, indentation, blank lines and spaces that don't separate tokens.
+# Kept: strings (verbatim), "--!" directive lines (--!optimize, --!native, ...), @native attributes, and one newline
+# wherever the source had one (so no ambiguous-call issues, and error line numbers stay roughly meaningful).
+#   python3 tools/minify.py IN OUT          # write minified IN to OUT
+#   python3 tools/minify.py --same-code F.. # check F.. have the same code tokens as `git show HEAD:F` (comment-only edits)
+#   python3 tools/minify.py --same-code-as OLD NEW  # same check between two files
+#   python3 tools/minify.py --test          # self-check
+import re, subprocess, sys
+from functools import lru_cache
+
+TOKEN = re.compile(r"""
+  (?P<ws>[ \t\r\n\f\v]+)
+| (?P<lcom>--\[(?P<ceq>=*)\[.*?\](?P=ceq)\])
+| (?P<com>--[^\n]*)
+| (?P<lstr>\[(?P<seq>=*)\[.*?\](?P=seq)\])
+| (?P<str>"(?:\\.|\\\n|[^"\\\n])*"|'(?:\\.|\\\n|[^'\\\n])*'|`(?:\\.|\\\n|[^`\\])*`)
+| (?P<num>0[xX][0-9a-fA-F_]*(?:\.[0-9a-fA-F_]*)?(?:[pP][+-]?\d+)?[uUlLi]*|0[bB][01_]+|(?:\d[\d_]*(?:\.[\d_]*)?|\.\d[\d_]*)(?:[eE][+-]?\d+)?[uUlLi]*)
+| (?P<name>@?[A-Za-z_]\w*)
+| (?P<op>\.\.\.|\.\.=|//=|\.\.|==|~=|<=|>=|//|::|->|[-+*/%^]=|.)
+""", re.S | re.X)
+
+def tokenize(src):
+    """[(kind, text, newline_before)]; comments/whitespace folded into newline_before ("--!" lines kept as 'dir')."""
+    out, nl, pos = [], False, 0
+    while pos < len(src):
+        m = TOKEN.match(src, pos)
+        kind, text = m.lastgroup, m.group(0)
+        if kind in ("ceq", "seq"): kind = "lcom" if text.startswith("--") else "lstr"
+        pos = m.end()
+        if kind == "ws" or kind == "lcom" or (kind == "com" and not text.startswith("--!")):
+            nl = nl or "\n" in text
+            continue
+        if kind == "com": kind = "dir"
+        if kind == "lstr" or kind == "str": kind = "str"
+        out.append((kind, text, nl))
+        nl = False
+    return out
+
+@lru_cache(maxsize=None)
+def glue_ok(a, b):
+    """True if `a..b` with no space still tokenizes as exactly a, b."""
+    if re.match(r"\w", a[-1]) and re.match(r"\w", b[0]): return False  # real lexers read `0then`/`x1` as one token
+    return [t for _, t, _ in tokenize(a + b)] == [a, b]
+
+def minify(src):
+    toks, out = tokenize(src), []
+    prev = None
+    for kind, text, nl in toks:
+        if prev is not None:
+            if nl or prev[0] == "dir" or kind == "dir": out.append("\n")
+            elif kind == "str" or prev[0] == "str":  # strings are self-delimiting; only `[` + `[[` would fuse
+                if kind == "str" and text[0] == "[" and prev[1].endswith("["): out.append(" ")
+            elif not glue_ok(prev[1], text):
+                out.append(" ")
+        out.append(text)
+        prev = (kind, text)
+    return "".join(out) + "\n"
+
+def code(src):
+    return [(k, t) for k, t, _ in tokenize(src)]
+
+def test():
+    cases = {
+        "local a = 1 -- c\nlocal b = a - -1\n": "local a=1\nlocal b=a- -1\n",
+        "x = 1 .. 2": "x=1 ..2\n",
+        "x = t[ [[s]] ]": "x=t[ [[s]]]\n",
+        "x = t[ [==[s]==] ]": "x=t[ [==[s]==]]\n",
+        "--!optimize 2\n--[[ long\ncomment ]] local s = 'a -- b' .. \"c\\\"d\"": "--!optimize 2\nlocal s='a -- b'..\"c\\\"d\"\n",
+        "@native\nfunction f(...) return ... end": "@native\nfunction f(...)return...end\n",
+        "a = b == c and d ~= e or f <= g": "a=b==c and d~=e or f<=g\n",
+        "x = 0x10 + 1e-5 + .5": "x=0x10+1e-5+.5\n",
+        "f(a)\n\n\n(g)(b)": "f(a)\n(g)(b)\n",
+        "s = [[a\n-- not a comment\n]]": "s=[[a\n-- not a comment\n]]\n",
+        "x = a / / b": "x=a/ /b\n",
+        "x = a . . b": "x=a. .b\n",
+        "if a == 0 then return 1 end": "if a==0 then return 1 end\n",
+        "x = 1 .. y": "x=1 ..y\n",
+    }
+    for src, want in cases.items():
+        got = minify(src)
+        assert got == want, (src, got, want)
+        assert code(minify(src)) == code(src), src
+    print("minify OK")
+
+if __name__ == "__main__":
+    if sys.argv[1] == "--test":
+        test()
+    elif sys.argv[1] in ("--same-code", "--same-code-as"):
+        bad = 0
+        pairs = [(sys.argv[2], sys.argv[3])] if sys.argv[1] == "--same-code-as" else [(None, f) for f in sys.argv[2:]]
+        for ref, f in pairs:
+            old = open(ref).read() if ref else subprocess.run(["git", "show", "HEAD:" + f], capture_output=True, text=True, check=True).stdout
+            a, b = code(old), code(open(f).read())
+            if a != b:
+                bad += 1
+                i = next((i for i, (x, y) in enumerate(zip(a, b)) if x != y), min(len(a), len(b)))
+                print("%s: CODE CHANGED at token %d: %r -> %r" % (f, i, a[i:i + 6], b[i:i + 6]))
+            else:
+                print("%s: same code" % f)
+        sys.exit(1 if bad else 0)
+    else:
+        src = open(sys.argv[1], encoding="utf-8").read()
+        dst = minify(src)
+        assert code(dst) == code(src), "minify changed code tokens"
+        open(sys.argv[2], "w", encoding="utf-8").write(dst)
+        print("wrote %s (%d -> %d bytes, %.0f%%)" % (sys.argv[2], len(src.encode()), len(dst.encode()), 100.0 * len(dst) / len(src)))

tools/test/run.py

@@ -16,6 +16,8 @@ G = "game, workspace, Instance, Enum, Vector2, Vector3, UDim2, Color3, Content,
 
 def build_run(args, flags):
     subprocess.run([sys.executable, os.path.join(ROOT, "tools", "bundle.py"), TMP] + (["--no-demo"] if os.environ.get("NO_DEMO") else []), check=True, stdout=subprocess.DEVNULL)
+    if os.environ.get("MINIFY"):  # test the minified bundle instead (error line numbers won't map back to sources)
+        subprocess.run([sys.executable, os.path.join(ROOT, "tools", "minify.py"), os.path.join(TMP, "ImGui.luau"), os.path.join(TMP, "ImGui.luau")], check=True, stdout=subprocess.DEVNULL)
     out = ["--" if args.roblox else "--!native", "--!optimize 2", flags, "local SOURCE_FNS = {}"]
     def add(key, path):
         s = "\n".join(l for l in open(path).read().split("\n") if not l.startswith("--!"))

tools/test/scripts/t_dock_close.luau

@@ -0,0 +1,68 @@
+-- Docked windows (floating split node) stop being submitted: the host lingers one frame, its bodies must be filled
+-- with the windows' bg colour (node.LastBgColor), not white, and everything must be gone within a few frames.
+local ReplicatedStorage = game:GetService("ReplicatedStorage")
+local RunService = game:GetService("RunService")
+local G = require(ReplicatedStorage:WaitForChild("ImGui"))
+local ImGui, ImVec2 = G.ImGui, G.ImVec2
+ImGui.CreateContext()
+local io = ImGui.GetIO()
+io.ConfigFlags = bit32.bor(io.ConfigFlags, G.ImGuiConfigFlags.DockingEnable)
+G.ImGui_ImplRoblox.Init()
+local frame, closed_at, done = 0, 31, false
+RunService.Stepped:Connect(function()
+    if done then return end
+    frame += 1
+    G.ImGui_ImplRoblox.NewFrame()
+    ImGui.NewFrame()
+    if frame == 2 then
+        local id = ImGui.GetID("floating")
+        ImGui.DockBuilderRemoveNode(id)
+        ImGui.DockBuilderAddNode(id, 0)
+        ImGui.DockBuilderSetNodePos(id, ImVec2(100, 100))
+        ImGui.DockBuilderSetNodeSize(id, ImVec2(600, 400))
+        local left, right = ImGui.DockBuilderSplitNode(id, G.ImGuiDir.Left, 0.5)
+        ImGui.DockBuilderDockWindow("A", left)
+        ImGui.DockBuilderDockWindow("B", right)
+        ImGui.DockBuilderFinish(id)
+    end
+    if frame < closed_at then
+        for _, n in { "A", "B" } do
+            if ImGui.Begin(n) then ImGui.Text("window " .. n) end
+            ImGui.End()
+        end
+    end
+    if frame == closed_at - 1 then
+        local a, b = ImGui.FindWindowByName("A"), ImGui.FindWindowByName("B")
+        assert(a.DockNode and b.DockNode and a.DockNode ~= b.DockNode and a.DockNode.HostWindow, "A, B docked side by side")
+    end
+    ImGui.Render()
+    local dd = ImGui.GetDrawData()
+    if frame >= closed_at then
+        for _, dl in dd.CmdLists:iter() do
+            -- white vertices spanning a big area = a white body fill (white text glyphs are small)
+            local vb, x0, y0, x1, y1 = dl.VtxBuffer.Buf, math.huge, math.huge, -math.huge, -math.huge
+            for _, pcmd in dl.CmdBuffer:iter() do
+                for i = pcmd.IdxOffset + 1, pcmd.IdxOffset + pcmd.ElemCount do
+                    local o = (pcmd.VtxOffset + dl.IdxBuffer.Data[i] - 1) * G.VTX_STRIDE
+                    if buffer.readu32(vb, o + 32) == 0xFFFFFFFF then
+                        local x, y = buffer.readf64(vb, o), buffer.readf64(vb, o + 8)
+                        x0, y0, x1, y1 = math.min(x0, x), math.min(y0, y), math.max(x1, x), math.max(y1, y)
+                    end
+                end
+            end
+            assert(not (x1 - x0 > 100 and y1 - y0 > 100), "white fill on frame " .. frame)
+        end
+        if dd.TotalVtxCount == 0 then
+            G.ImGui_ImplRoblox.RenderDrawData(dd)
+            for _, set in io.BackendPlatformUserData.Layers do
+                for kind = 1, 3 do assert(not (set[kind] and set[kind].Visible), "backend layer still visible after close") end
+            end
+            print("DOCK CLOSE OK after", frame - closed_at + 1, "frames")
+            done = true
+            return
+        else
+            assert(frame < closed_at + 3, "docked windows still drawn " .. (frame - closed_at + 1) .. " frames after close")
+        end
+    end
+    G.ImGui_ImplRoblox.RenderDrawData(dd)
+end)

tools/test/scripts/t_fixes.luau

@@ -0,0 +1,57 @@
+-- Regressions vs upstream: clipboard paste filter (InputTextEx), ImParseFormatTrimDecorations (Ctrl+click temp input), ShrinkWidths tie order
+local G = require(game:GetService("ReplicatedStorage"):WaitForChild("ImGui"))
+local ImGui, ImVec2 = G.ImGui, G.ImVec2
+ImGui.CreateContext(); G.ImGui_ImplRoblox.Init()
+local io = ImGui.GetIO()
+local failed = {}
+local function check(ok, msg) if not ok then table.insert(failed, msg); print("FAIL " .. msg) end end
+
+-- ShrinkWidths: equal widths sort by Index descending (upstream ShrinkWidthItemComparer), so the rounding remainder goes to the highest Index first
+local items = {}
+for i = 1, 4 do local it = G.ImGuiShrinkWidthItem(); it.Index = i - 1; it.Width = 100; it.InitialWidth = 100; items[i] = it end
+ImGui.ShrinkWidths(items, 1, 4, 2.0, 10.0)
+local w = {}
+for _, it in items do w[it.Index] = it.Width end
+check(w[3] == 100 and w[2] == 100 and w[1] == 99 and w[0] == 99, ("ShrinkWidths widths %s %s %s %s"):format(w[0], w[1], w[2], w[3]))
+
+local function edit_text()
+    local st = ImGui.GetCurrentContext().InputTextState
+    return G.ImGui._ByteArrayToString(st.TextA.Data, 1, st.TextLen + 1)
+end
+local buf = ImGui.NewTextBuffer("", 64)
+local f, sf, di = 0, 45.0, 50
+local rects = {}
+local function rect() local a, b = ImGui.GetItemRectMin(), ImGui.GetItemRectMax(); return { ImVec2(a.x, a.y), ImVec2(b.x, b.y) } end -- copies: GetItemRectMin() returns the live LastItemData.Rect.Min
+local function click(name, ctrl)
+    local r = rects[name]
+    io:AddMousePosEvent((r[1].x + r[2].x) / 2, (r[1].y + r[2].y) / 2)
+    if ctrl then io:AddKeyEvent(G.ImGuiMod_Ctrl, true) end
+    io:AddMouseButtonEvent(0, true)
+end
+local function release() io:AddMouseButtonEvent(0, false); io:AddKeyEvent(G.ImGuiMod_Ctrl, false) end
+local function key(k) io:AddKeyEvent(k, true); io:AddKeyEvent(k, false) end
+
+game:GetService("RunService").Stepped:Connect(function()
+    f += 1
+    G.ImGui_ImplRoblox.NewFrame()
+    if f == 3 then click("t") elseif f == 4 then release() end
+    -- clipboard: tab is filtered out (single line, no AllowTabInput), é is 2 bytes
+    if f == 6 then ImGui.SetClipboardText("ab\tc\u{e9}"); io:AddKeyEvent(G.ImGuiMod_Ctrl, true); io:AddKeyEvent(G.ImGuiKey.V, true) end
+    if f == 7 then io:AddKeyEvent(G.ImGuiKey.V, false); io:AddKeyEvent(G.ImGuiMod_Ctrl, false) end
+    if f == 9 then key(G.ImGuiKey.Escape) end
+    if f == 11 then click("s", true) elseif f == 12 then release() end
+    if f == 14 then key(G.ImGuiKey.Escape) end
+    if f == 16 then click("d", true) elseif f == 17 then release() end
+    ImGui.NewFrame()
+    ImGui.SetNextWindowPos(ImVec2(10, 10)); ImGui.SetNextWindowSize(ImVec2(300, 200))
+    ImGui.Begin("T")
+    ImGui.InputText("##t", buf, 64); rects.t = rect()
+    sf = ImGui.SliderFloat("##s", sf, 0.0, 100.0, "%.0f deg"); rects.s = rect()
+    di = ImGui.DragInt("##d", di, 1, 0, 100, "%d%%"); rects.d = rect()
+    ImGui.End()
+    ImGui.Render(); G.ImGui_ImplRoblox.RenderDrawData(ImGui.GetDrawData())
+    if f == 8 then check(edit_text() == "abc\u{e9}", "paste: '" .. edit_text() .. "'") end
+    if f == 13 then check(edit_text() == "45", "SliderFloat temp input: '" .. edit_text() .. "'") end
+    if f == 18 then check(edit_text() == "50", "DragInt temp input: '" .. edit_text() .. "'") end
+    if f == 20 and #failed == 0 then print("FIXES OK") end
+end)

wally.toml

@@ -1,6 +1,6 @@
 [package]
 name = "4dbug/imgui-luau"
-version = "0.1.2"
+version = "0.1.4"
 registry = "https://github.com/UpliftGames/wally-index"
 realm = "shared"
 license = "MIT"