gui_toolkit 0.9.3

Color glyphs in every format

• Direct2D draws color glyphs (font/color.odin, bindings in font/d2d.odin): COLR v1 paint trees (linear,
  radial and sweep gradients with their extend modes, transforms, PaintComposite modes, clip boxes, PaintColrGlyph),
  COLR v0 layers, sbix / CBDT / PNG bitmaps and OT-SVG (plain or gzip) are drawn on a private WARP device into a
  bitmap read back into the atlas' Color pages. Windows 11 22H2 and later: ID2D1DeviceContext7::DrawGlyphRunWithColorSupport;
  Windows 10 1607 and later: the runs of TranslateColorGlyphRun drawn by the call of their format (no paint trees:
  v0 layers or the outline); without Direct2D: COLR v0 layers composited on the CPU as before. Whether a glyph is a
  color glyph comes from IDWriteFactory8::TranslateColorGlyphRun (paint trees) or IDWriteFactory4's.
• Text-color layers (palette entry 0xFFFF, COLR v1 foreground paints, SVG currentColor) take the text color: a
  color glyph is drawn in two colors once to find whether it depends on it; such glyphs are kept once per text color.
  font.glyph_image gains an fg parameter (sRGB, default black); draw.glyph_run passes the run's color.
  Glyph_Image.uses_fg.
• font.color_renderable(s, id): false for a face whose only color format the system cannot draw (COLR v1 before
  Windows 11 22H2): a cascade should take those characters elsewhere rather than show outlines.
• Faces with only COLR v1 (DWRITE_GLYPH_IMAGE_FORMATS_COLR_PAINT_TREE) count as color faces. Whether a COLR v1 glyph
  uses the text color comes from its paint attributes (IDWriteFontFace7::CreatePaintReader), of a COLR v0 glyph from
  its layers; only SVG glyphs are drawn twice to find out.
• Off the drawing thread (Settings.color_async, off by default): a complex color glyph costs milliseconds (a
  Segoe UI Emoji COLR v1 emoji: about 4 ms on WARP). The first lookup queues it and returns a pending image
  (Glyph_Image.pending); one thread draws the queue, puts the bitmaps in the atlas and calls
  font.set_color_ready_callback's callback (ask for a frame there). font.color_ready_generation,
  font.color_pending, font.color_wait. A picture recorded while one of its glyphs was pending is stale once the
  ready generation moves (Picture.glyphs_pending, pending_ready; checked before the empty-picture cull).
  unload drops a face's queued requests and waits for the one in flight; destroy stops the thread.
• tests/color_glyphs: Google's COLR v1 test glyphs (gradient ends and middle, sweep quadrants, radial, composite,
  rotate / skew / transform, foreground paints in two text colors), Twemoji sbix / OT-SVG / OT-SVGZ smileys, the
  ChromaCheck CBDT glyph, color glyphs off, and the same glyphs drawn through the draw layer (WARP).

Masks

• draw.push_mask(dc, bounds, fx), draw.mask_layer(dc, mode, op), draw.pop_mask(dc) (draw/mask.odin): content
  drawn into a layer, multiplied by the coverage of mask layers drawn after it, each by its alpha or its luminance
  (Mask_Mode), composited with the layers below it by Mask_Op (add, subtract, intersect, exclude: CSS
  mask-composite); then filters, opacity and blend mode as push_effects. Mask layers draw in sRGB. Without a render
  target (or in a picture) the content is drawn unmasked and the mask layers are cut away. CSS mask-image and
  background-clip: text are drawn with it.
• render.Pass_Mode.Mask (render/filter.hlsl), PASS_MASK_LUMINANCE, PASS_MASK_DEST, PASS_MASK_APPLY,
  MASK_OP_SHIFT, render.Mask_Op. pop_layer closes a mask too.
• tests/masks (both blend spaces): alpha and luminance coverage, the four operators, a gradient mask under opacity
  and a clip, no mask layer, text as a mask (background-clip: text), the fallback inside a picture.