Add gradient brush ABI support (LinearGradientBrush/RadialGradientBrush) - #7
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Marc-André Moreau (mamoreau-devolutions) merged 2 commits intoSep 12, 2026
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Introduces IAvnGradientBrush/IAvnLinearGradientBrush/IAvnRadialGradientBrush as new sibling COM interfaces alongside the existing solid-only IAvnBrush (v1 unchanged). IAvnControlFactory gains create_linear_gradient_brush and create_radial_gradient_brush, requiring its IID to move from ABI version 13 to 14. - C# IR/generator layer emits the new interfaces, native header, and factory methods (IR schema bumped to v17). - Rust avalonia-sys exposes the raw vtables/structs; avalonia adds safe LinearGradientBrush/RadialGradientBrush/Paint/GradientStop/SpreadMethod/ RelativePoint/RelativeScalar types. - Existing chrome properties (Background/BorderBrush/Foreground) remain solid-brush-only by design; reading a gradient there still returns AVN_E_NONSOLIDBRUSH. - Updates hardcoded factory ABI version expectations (13->14) across the C# and Rust ABI test suites, and adds new tests covering the gradient interfaces' shapes/IIDs and safe-API value semantics. - Documents the new capability in MARSHALLING.md/README.md/COMPATIBILITY.md and bumps release-manifest.json's projectionIr schema to 17.
…lid-only A rubber-duck review of PR #7 caught a real regression: the generator's FromBrush/ToBrush helpers (used by every existing Background/BorderBrush/ Foreground getter and setter) special-cased gradient brushes, silently routing them through the solid-only IAvnBrush property path instead of throwing AVN_E_NONSOLIDBRUSH as documented and originally tested. This contradicted the PR's own stated scope decision (existing chrome properties stay solid-brush-only in this wave) and broke BrushMemberComTests.A_non_solid_brush_fails_explicitly_instead_of_picking_a_nearest_colour. Fix: remove the gradient special-casing from ComSourceEmitter's emitted FromBrush/ToBrush methods, restoring the solid-only behavior for existing properties. Gradient objects still separately implement IAvnBrush at the class level (AvnLinearGradientBrush/AvnRadialGradientBrush), where GetColor correctly returns AVN_E_NONSOLIDBRUSH by design - that path was already correct and is unchanged. No ABI/IID/header changes result from this fix (regenerated header/IR/ Rust bindings are byte-identical); only IAvnBrush.g.cs's static helper methods changed. Verified: Avalonia.Host.Tests 375/375 pass (was 374/375), Avalonia.Projection.Ir.Tests 129/129 pass, and the full non-host-dependent Rust test suite passes.
Marc-André Moreau (mamoreau-devolutions)
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September 12, 2026 14:35
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Summary
Expands Avalonia API coverage in Rustolonia with gradient brush support (
LinearGradientBrush/RadialGradientBrush), following the existing "sibling interface + QueryInterface" versioning pattern.What changed
IAvnGradientBrush/IAvnLinearGradientBrush/IAvnRadialGradientBrush.IAvnBrushv1 (solid-color only) is untouched.IAvnControlFactorygainscreate_linear_gradient_brush/create_radial_gradient_brush, which required bumping its deterministic IID from ABI version 13 → 14.ProjectionIrv16→17) + generator emits the new interfaces, native header, and factory methods.avalonia-sysexposes the raw vtables/structs.avaloniaadds safeLinearGradientBrush,RadialGradientBrush,Paint,GradientStop,SpreadMethod,RelativePoint,RelativeScalartypes.Background/BorderBrush/Foreground) remain solid-brush-only — reading a gradient-backed brush off them still returnsAVN_E_NONSOLIDBRUSH. Wiring gradients into control properties is left for a future wave.ClrTypeExtractorTests.cs) and Rust (brush_abi.rs,control_abi.rs,definitions_abi.rs,wave_a_abi.rs…wave_k_abi.rs) ABI test suites.rust/avalonia-sys/tests/gradient_brush_abi.rs(interface shapes/IIDs/vtable slots) andrust/avalonia/tests/gradient_brush_round_trip.rs(safe-API value semantics).rust/MARSHALLING.md(new "Gradient brushes" section),rust/README.md,rust/COMPATIBILITY.md(IR v17 + gradient-wave ABI notes).rust/release-manifest.jsonbumped to IR v17.Testing
cargo test -p avalonia-sys --locked: 77/77 passing (excludes pre-existing host-binary-dependentnativeaot_fixturetests, unrelated/environment-gated).cargo test -p avalonia --locked: all passing.cargo test -p avalonia-bindgen --locked: 50/50 passing.dotnet test tests\Avalonia.Projection.Ir.Tests\Avalonia.Projection.Ir.Tests.csproj -c Release: 129/129 passing.dotnet build host\Avalonia.Host.csproj -c Release: succeeded, 0 errors.