VENDORED_SKIA_MODS.md

Vendored Skia Dart Modifications

This file records local changes made under third_party/skia_dart so we can track the delta from the published package and avoid losing rendering-critical API work during future vendor refreshes.

2026-06-10: Dart Gradient Shader API Surface

Purpose:

• Keep missing Skia APIs in the vendored implementation instead of adding renderer-side workarounds.
• Expose Skia gradient shader creation through typed Dart APIs so the rendering port can call Skia directly.

Files changed:

• third_party/skia_dart/packages/skia_dart/lib/src/shader.dart
• third_party/skia_dart/packages/skia_dart/lib/src/skia.g.dart

Changes:

• Added Dart FFI bindings for:
  • sk_shader_new_linear_gradient
  • sk_shader_new_radial_gradient
  • sk_shader_new_sweep_gradient
  • sk_shader_new_two_point_conical_gradient
• Added typed SkShader factories for:
  • SkShader.linearGradient
  • SkShader.radialGradient
  • SkShader.sweepGradient
  • SkShader.twoPointConicalGradient
• Added shared gradient color/position pointer plumbing for the new factories.

Notes:

• This API surface was added before the native dylib had matching exported symbols. The native wrapper work below makes the Dart bindings resolvable at runtime.

2026-06-10: Native Gradient Shader Wrapper and Rebuild

Purpose:

• Enable full Skia-backed gradient rendering from Dart without pre-rasterizing gradient pixels in the rendering port.
• Make the existing Dart gradient shader API resolve against the vendored native dylib.

Files changed:

• third_party/skia_dart/src/wrapper/include/sk_shader.h
• third_party/skia_dart/src/wrapper/sk_shader.cpp
• third_party/skia_dart/src/wrapper/sk_surface.cpp

Changes:

• Re-enabled the native C wrapper declarations for Skia gradient shader creation so the dylib exports unmangled C symbols.
• Ported the native gradient wrapper from the older SkGradientShader::Make* API to current Skia's SkShaders::*Gradient API using SkGradient, SkGradient::Colors, SkSpan, and SkColor4f.
• Preserved the existing C ABI shape by converting legacy SkColor arrays to SkColor4f arrays inside the native wrapper.
• Updated sk_surface_write_pixels for current Skia, replacing the removed five-argument SkSurface::writePixels overload with SkPixmap construction plus the current three-argument call.

Native rebuild:

• Synced Skia third-party dependencies with python3 bin/sync.
• Rebuilt third_party/skia_dart/out/mac_arm64_graphite/libskia_dart.dylib using third_party/ninja/ninja -C ../out/mac_arm64_graphite libskia_dart.dylib.
• Copied the rebuilt dylib to third_party/skia_dart/packages/skia_dart/.dart_tool/lib/libskia_dart.dylib for local Dart test execution.

Verification:

• nm -gU third_party/skia_dart/out/mac_arm64_graphite/libskia_dart.dylib | rg "sk_shader_new_(linear|radial|sweep|two_point)"
• nm -gU third_party/skia_dart/packages/skia_dart/.dart_tool/lib/libskia_dart.dylib | rg "sk_shader_new_(linear|radial|sweep|two_point)"

Both dylibs export:

• _sk_shader_new_linear_gradient
• _sk_shader_new_linear_gradient_color4f
• _sk_shader_new_radial_gradient
• _sk_shader_new_radial_gradient_color4f
• _sk_shader_new_sweep_gradient
• _sk_shader_new_sweep_gradient_color4f
• _sk_shader_new_two_point_conical_gradient
• _sk_shader_new_two_point_conical_gradient_color4f

Generated/Local Build Artifacts

The following paths are local build outputs or dependency checkouts created to rebuild the vendored native library; they are not hand-authored source changes:

• third_party/skia_dart/skia/
• third_party/skia_dart/out/
• third_party/skia_dart/packages/skia_dart/.dart_tool/lib/libskia_dart.dylib