Strict source rect for sub-rect image draws (flutter/flutter#67881) - #1
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Strict source rect for sub-rect image draws (flutter/flutter#67881)#1lslv1243 wants to merge 3 commits into
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Canvas::drawImageRect always passed SrcRectConstraint::kFast, so atlas cell draws could sample neighbouring cells. Pass kStrict whenever the source rect is a strict sub-rect of the image; full-image draws keep kFast semantics. Also forward the constraint in the Impeller dispatcher, which received it and dropped it (the canvas + TextureContents strict pipeline already existed, unwired). Validated on iOS sim + macOS: sentinel-atlas bleed 0/56 configs on both Skia and Impeller at FilterQuality.none and .low (stock: 3-30/56 none, 56/56 low).
…urce is set DrawImageRect renders the given texture; the paint's color source is irrelevant to it. Dispatchers persist paint attributes across ops and image draws do not re-sync the color source, so a preceding ImageShader draw leaves paint.color_source set. Paint::WithColorFilter's image-source early-return then assumes the color filter was applied by TiledTextureContents and drops it silently. Repro: draw a rect with an ImageShader paint, then drawImageRect with a ColorFilter - the filter is ignored (e.g. mask recolors render raw pixels). Fix: clear the color source on a local paint copy before building the texture entity. Upstream master retains the same early-return; recording-order changes currently mask it there.
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Fixes two rendering defects for Fibula Wars, at the engine root, on Flutter 3.27.1 (
cb4b5fff73).1. Strict source rect for sub-rect image draws (flutter/flutter#67881)
Canvas::drawImageRecthardcodedDlSrcRectConstraint::kFast, so sampling reads outside the source rect and atlas cells bleed into neighbours. This PR passeskStrictwhenever the source rect does not cover the whole image:lib/ui/painting/canvas.cc: conditional strict constraint.impeller/display_list/dl_dispatcher.cc: forward the constraint to the Impeller canvas — the strict sampling pipeline existed upstream but the dispatcher dropped the parameter (still true on master as of 2026-08-01).Validated with a sentinel-atlas harness (every neighbour cell magenta): 0/56 bleeding configs at both filter qualities on iOS (Skia Metal + Impeller Metal, sim debug + device release), Android emulator (Skia GL) and Android device (Impeller GLES). Bilinear atlas draws become pixel-identical to isolated textures (0/280).
2. Impeller: stale image color source suppresses texture-draw color filters
Paint::WithColorFilterearly-returns whencolor_sourceis an image color source, assumingTiledTextureContentsapplied the filter. But dispatchers persist paint attributes across ops and image draws don't re-sync the color source — so after anyImageShaderdraw in the same display list, every laterdrawImageRectwith aColorFiltersilently loses the filter (e.g. recolorable masks render their raw pixels).Minimal repro: draw a fullscreen rect with an
ImageShaderpaint, thendrawImageRectwithColorFilter.mode(green, srcIn)+BlendMode.multiplyover a gray base — renders raw red instead of green. Fix:Canvas::DrawImageRectclearscolor_sourceon a local paint copy (the texture is the source; the attribute is irrelevant there). Verified: filtered output returns to the mathematically expected value; full game mask-tint pipeline renders correctly over shader-painted backgrounds.Upstream note: master retains the same early-return; current recording behavior happens to mask the bug there, but the hardening is applicable as-is.
Build compatibility (Xcode 26 / macOS 26 SDK)
Building this 2024-era checkout with Xcode 26 needs two buildroot/libcxx patches, carried in the sibling repos:
math.h: restore C99 classification macros for C++ TUs.-iframework .../SubFrameworksso UIKit's UIUtilities import resolves.