gui_toolkit 0.17.0

Added

• Planes that cut through each other (draw/bsp.odin): draw.draw_planes(dc, items) draws the planes of one 3D rendering context in the order they hide each other, and when planes cut through each other (or hide each other in a cycle) splits them along each other's planes by a BSP (as Chromium's BspTree / DrawPolygon), the pieces ordered back to front for a viewer in front. A piece is the plane's layer drawn again under Plane_Draw.cuts (Plane_Cut: half-spaces of the space after the perspective divide, at most MAX_PLANE_CUTS, tested per pixel on the interpolated plane position in rect.wgsl: no seams between pieces). Plane_Item.parts: several layers on one plane (a plane and what rides on it) are cut and ordered together.
• Effects on the composite of a plane: Plane_Draw.blend (mix-blend-mode of the projected quad), backdrop + shape (backdrop-filter filtered in screen space, shown through the alpha of a layer projected like the plane).
• Sharp planes: Plane_Fx.mips gives a plane's layer a mip chain (render.acquire_target_mips, render.target_mips_supported, Op_Kind.Mips on D3D11 and wgpu); the projected quad's filter is anisotropic along the long axis of the footprint at the mip level of the short axis (proj_texel). FLAG_PROJECT instances take a frame rect (the antialiased edge, for a quad that is one piece of a larger plane) and the valid texel range of the layer (colors[2], colors[3]). draw.open_plane_frame (map a pointer back through a plane exactly).
• tests/planes: planes crossing in an X (both orders of drawing give the same picture, with and without perspective), a star of three, blend on a flat and a turned plane, backdrop-filter through a silhouette, mip levels against aliasing; D3D11 and wgpu.
• A COLR / CPAL interpreter (font/colr.odin, colr_raster.odin, colr_glyph.odin): Settings.color_engine = .Builtin draws COLR v0 and v1 color glyphs (gradients, transforms, the 28 composite modes, clip boxes, text-color paints) on the CPU from the face's own tables, the same on every platform, into the Color atlas pages (so also async, per text color, in pictures). Default .System (Direct2D), unchanged. colr_samples, colr_cache_kb, colr_counts, colr_of, colr_dump; Colr / colr_open / colr_render for the portable core. A graph it refuses (cycle, bad offset) shows the glyph's outline.
• Built-in emoji: font.set_emoji_source(s, path | data): an emoji font loaded on first need, used for emoji characters before the system fallback (font/emoji.odin, emoji_data.odin generated from Unicode 18 emoji-data.txt by tools\gen_emoji_data.ps1). Tag sequences are formed from the face's GSUB ccmp ligatures (colr_gsub.odin).
• tools\fetch_emoji.ps1 (Noto Color Emoji COLR v1, pinned by commit and SHA-256, OT-SVG table dropped: 4.9 MiB), font/data/NotoColorEmoji-OFL.txt, tools/colrcompare (interpreter against Direct2D), tools/colrboard + tools\emoji_board.ps1 (against Chrome / Edge), tools/emojiperf, tests/colr (also tests/color_glyphs -define:COLR_ENGINE=builtin).

Changed

• rect.wgsl: two more flat varyings (the cuts of a projected quad); HLSL regenerated. ui.VERSION and the version constants agree again (they said 0.16.0 and 0.15.0).