Skia parity: premultiplied rendering, layer effects, and WebGPU interop rework

.gitattributes

@@ -84,12 +84,15 @@
 #   treat as binary
 ###############################################################################
 *.basis             binary
+*.a                 binary
 *.dll               binary
+*.dylib             binary
 *.exe               binary
 *.pdf               binary
 *.ppt               binary
 *.pptx              binary
 *.pvr               binary
+*.so                binary
 *.snk               binary
 *.xls               binary
 *.xlsx              binary

.github/copilot-instructions.md

@@ -0,0 +1,3 @@
+# GitHub Copilot Instructions
+
+Read and follow [AGENTS.md](../AGENTS.md) as the repository-wide source of coding, performance, and verification requirements. Prefer existing local patterns and repository configuration whenever generated code or suggestions are accepted.

.gitignore

@@ -231,3 +231,6 @@ SixLabors.Shapes.Coverage.xml
 .dotnet
 .codex-*
 .claude
+/plans/
+
+samples/Avalonia**

AGENTS.md

@@ -0,0 +1,41 @@
+# Six Labors AI Coding Guidelines
+
+These instructions apply to the entire repository. More-specific `AGENTS.md` files may add to or override them for their directory tree.
+
+## Working Practices
+
+- Inspect the relevant implementation, tests, benchmarks, project files, and nearby code before proposing or making changes. Do not infer current behavior when the source is available.
+- Make the smallest complete change that solves the requested problem. Avoid unrelated cleanup, speculative abstractions, and formatting churn.
+- Match established architecture, naming, formatting, documentation, and test patterns. Treat `.editorconfig`, analyzers, and repository build settings as authoritative.
+- Preserve public API and observable behavior unless the task explicitly requires a change. Public API documentation must describe observable behavior, not implementation details.
+- Do not use reflection against built assemblies, ad hoc assembly loading, or temporary probe projects unless explicitly requested.
+- Build .NET projects in Release configuration unless explicitly instructed otherwise.
+
+## Performance
+
+- Treat throughput, latency, memory use, and binary size as design constraints, especially in pixel-processing, drawing, parsing, encoding, and other hot paths.
+- Avoid unnecessary allocations, copies, boxing, closures, interface dispatch, repeated enumeration, and extra passes over data.
+- Reuse the repository's existing memory ownership, pooling, span, vectorization, and parallelization patterns. Do not introduce a new mechanism when an established one fits.
+- Keep hot loops simple and bounds-check-friendly. Hoist invariant work, preserve locality, and use the narrowest suitable data types without sacrificing correctness.
+- Do not trade correctness or maintainability for assumed speed. Support non-obvious optimizations with measurements or clear evidence, and add or update benchmarks when performance is the purpose of the change.
+- Consider all supported target frameworks and runtime capabilities. Do not regress fallback paths while optimizing newer runtimes.
+
+## C# Conventions
+
+- Follow the existing code around the change; local patterns take precedence over generic preferences.
+- Do not use `record` or `record struct` types.
+- Prefer established invariants over redundant guards. Validate at real external boundaries and do not add defensive checks for internally controlled states.
+- Do not extract single-use helpers merely to name a block. Extract only for genuine reuse, an established local pattern, or meaningful complexity reduction.
+- Add vertical whitespace after multi-line statements and declarations and between distinct logical stages. Never add trailing whitespace.
+- Document every method, constructor, and property, regardless of whether it is public, internal, protected, or private. Keep public API documentation limited to observable behavior; use private and internal documentation to capture the contract and intent needed to maintain the code.
+- Add inline comments throughout complex code. Explain algorithms, formulas, invariants, ownership, compatibility behavior, and performance tradeoffs at the operations and decisions they govern. Explain why the code is shaped that way rather than narrating the syntax.
+- Document SIMD code especially thoroughly. Explain the vector layout, lane meaning, widening or narrowing, masks, shuffles, constants, alignment or remainder handling, supported instruction paths, scalar equivalence, and the reason each non-obvious operation is correct.
+- Write algorithm and SIMD comments for a maintainer who is unfamiliar with the implementation. The reader should not need to reconstruct intent from external documentation, issue history, or benchmark results.
+
+## Verification
+
+- Add or update focused tests when behavior changes, following the test framework and conventions already used by the project.
+- Never hack, weaken, skip, conditionally bypass, or otherwise manipulate a test to make it pass. Fix the production defect or the genuine test defect while preserving the test's intended coverage and sensitivity.
+- Do not update golden files, reference images, snapshots, baselines, or expected-output artifacts to resolve a test failure. Treat a mismatch as evidence to investigate and correct the implementation.
+- Run the narrowest relevant formatting, test, and Release build commands, then expand verification in proportion to the risk and scope of the change.
+- Report what changed, the verification performed, and any remaining risks or unverified assumptions.

CLAUDE.md

@@ -0,0 +1,3 @@
+# Claude Code Instructions
+
+Read and follow [AGENTS.md](AGENTS.md) as the repository-wide source of coding, performance, and verification requirements. Apply any more-specific `AGENTS.md` or `CLAUDE.md` found below the files being changed.

GEMINI.md

@@ -0,0 +1,3 @@
+# Gemini CLI Instructions
+
+Read and follow [AGENTS.md](AGENTS.md) as the repository-wide source of coding, performance, and verification requirements. Apply any more-specific `AGENTS.md` or `GEMINI.md` found below the files being changed.

samples/DrawShapesWithImageSharp/Program.cs

@@ -157,24 +157,15 @@ private static void DrawPosterComposition()
 
             canvas.Fill(Brushes.Solid(Color.SeaGreen), shorelineShape);
 
-            // Clipping demo: canvas.Save accepts a clip path plus DrawingOptions whose
-            // BooleanOperation controls how the new clip combines with the existing one. Using
-            // Intersection means subsequent draws are masked to the oval highlight shape, so a
-            // rectangular gradient fill can be reused without re-shaping it as an ellipse.
             EllipsePolygon lakeHighlight = new(725, 512, 285, 86);
-            DrawingOptions lakeHighlightClipOptions = new()
-            {
-                ShapeOptions = new ShapeOptions
-                {
-                    BooleanOperation = BooleanOperation.Intersection
-                }
-            };
 
             RectangleF lakeHighlightBounds = lakeHighlight.Bounds;
 
-            // Save pushes a clipping state; Restore pops it. Anything drawn between the two is
+            // Save pushes a state; Clip narrows it. Anything drawn between the two is
             // confined to lakeHighlight even though the brush spans its full bounding rectangle.
-            canvas.Save(lakeHighlightClipOptions, lakeHighlight);
+            canvas.Save();
+            canvas.Clip(lakeHighlight);
+
             canvas.Fill(Brushes.ForwardDiagonal(Color.White.WithAlpha(.36F), Color.Transparent), new RectanglePolygon(lakeHighlightBounds));
             canvas.Restore();
 
@@ -910,7 +901,7 @@ private static void DrawImageProcessingMask()
 
             canvas.DrawText(
                 new RichTextOptions(subtitleFont) { Origin = new PointF(40, 66) },
-                "Apply() runs a processor inside an IPath, ImageBrush fills one with a photo, and Save() clips drawing to one.",
+                "Apply() runs a processor inside an IPath, ImageBrush fills one with a photo, and Clip() limits drawing to one.",
                 Brushes.Solid(secondaryColor),
                 pen: null);
 
@@ -1068,20 +1059,15 @@ static void DrawPhotoInTextPanel(
                     imageArea.Y + ((imageArea.Height - textBounds.Height) / 2F) - textBounds.Y),
             };
 
-            // GeneratePaths returns one IPath per glyph. canvas.Save accepts params IPath[] so
-            // the whole collection becomes a compound clip, but ShapeOptions.BooleanOperation
-            // must be set to Intersection: the default Difference would cut the glyph shapes
-            // OUT of the photograph, the opposite of "image inside text".
+            // GeneratePaths returns one IPath per glyph. Clip accepts params IPath[] so
+            // the whole collection becomes one compound clip for the photograph.
             IPathCollection letters = TextBuilder.GeneratePaths("MASK", glyphOptions);
             IPath[] glyphClips = [.. letters];
 
-            DrawingOptions clipToGlyphs = new()
-            {
-                ShapeOptions = new ShapeOptions { BooleanOperation = BooleanOperation.Intersection },
-            };
-
             canvas.Fill(Brushes.Solid(Color.ParseHex("#E2DCC2")), new RectanglePolygon(imageArea));
-            canvas.Save(clipToGlyphs, glyphClips);
+            canvas.Save();
+            canvas.Clip(glyphClips);
+
             canvas.DrawImage(source, source.Bounds, imageArea, null);
             canvas.Restore();
 

samples/DrawShapesWithImageSharp/README.md

@@ -9,7 +9,7 @@ Poster-style landscape that exercises the building blocks:
 
 - `LinearGradientBrush` and `RadialGradientBrush` for the sky, lake, and sun.
 - `PathBuilder` + `CloseFigure` for the mountain ridges, lake, and shoreline.
-- `canvas.Save(options, IPath)` with `BooleanOperation.Intersection` for the lake highlight clip.
+- `canvas.Save()` plus `canvas.Clip(IPath)` for the lake highlight clip.
 - `canvas.Save` + `canvas.SaveLayer` to apply a Z rotation and then composite the title panel and text together with `GraphicsOptions.BlendPercentage`.
 - `TextMeasurer.MeasureRenderableBounds` to size the title panel to the laid-out text.
 
@@ -38,7 +38,7 @@ Image-compositing scene demonstrating four ways a photograph (`tests/Images/Inpu
 - **Before / after wipe** — `canvas.Apply(rightHalfRect, ctx => ctx.OilPaint(15, 5))` scopes an `OilPaint` processor to the right half of the photograph.
 - **Privacy redaction** — `canvas.Apply(ellipse, ctx => ctx.Pixelate(10))` pixelates an elliptical face-shaped region and leaves the rest untouched.
 - **Image as a brush** — `new ImageBrush<Rgba32>(source, source.Bounds, brushOffset)` wraps the photograph as a `Brush` so a `StarPolygon` path can be filled with it as a texture; the brush offset aligns the mountain in the photograph with the star's centre.
-- **Photo in text** — `TextBuilder.GeneratePaths("MASK", ...)` produces one `IPath` per glyph; `canvas.Save(intersectionOptions, glyphPaths)` uses them as a compound clip so `DrawImage` only renders inside the letterforms.
+- **Photo in text** — `TextBuilder.GeneratePaths("MASK", ...)` produces one `IPath` per glyph; `canvas.Clip(glyphPaths)` uses them as a compound clip so `DrawImage` only renders inside the letterforms.
 
 ## Running
 

samples/WebGPUExternalSurfaceDemo/Controls/WebGPURenderControl.cs

@@ -17,7 +17,9 @@ public sealed partial class WebGPURenderControl : Control
 {
     private const int WM_MOVING = 0x0216;
     private const int WM_EXITSIZEMOVE = 0x0232;
+    private static readonly nint ProcessModuleHandle = GetModuleHandle(null);
 
+    private readonly WebGPUSurfaceSession surfaceSession;
     private WebGPUExternalSurface? surface;
     private Size framebufferSize;
     private bool idleHooked;
@@ -29,8 +31,11 @@ public sealed partial class WebGPURenderControl : Control
     /// <summary>
     /// Initializes a new instance of the <see cref="WebGPURenderControl"/> class.
     /// </summary>
-    public WebGPURenderControl()
+    /// <param name="surfaceSession">The session shared by the application's related presentation surfaces.</param>
+    public WebGPURenderControl(WebGPUSurfaceSession surfaceSession)
     {
+        this.surfaceSession = surfaceSession;
+
         // WebGPU presents directly to the native surface. Normal WinForms buffering and background
         // painting would add flicker or unnecessary work, so the control opts into direct user painting.
         this.SetStyle(
@@ -81,12 +86,12 @@ protected override void OnHandleCreated(EventArgs e)
             Math.Max(this.framebufferSize.Width, 1),
             Math.Max(this.framebufferSize.Height, 1));
 
-        // The module handle is required by the Win32 surface descriptor. It identifies the process module
-        // that owns the window class backing this control.
-        this.surface = new WebGPUExternalSurface(
+        // WinForms registers its window classes against the process executable module. Use that same
+        // HINSTANCE in the WebGPU descriptor instead of the managed assembly's module handle.
+        this.surface = this.surfaceSession.CreateSurface(
             WebGPUSurfaceHost.Win32(
                 this.Handle,
-                Marshal.GetHINSTANCE(typeof(WebGPURenderControl).Module)),
+                ProcessModuleHandle),
             initialFramebufferSize,
             new WebGPUExternalSurfaceOptions
             {
@@ -322,5 +327,8 @@ private struct NativeMessage
     [LibraryImport("user32.dll", EntryPoint = "PeekMessageW")]
     private static partial int PeekMessage(out NativeMessage msg, nint hWnd, uint messageFilterMin, uint messageFilterMax, uint flags);
 
+    [LibraryImport("kernel32.dll", EntryPoint = "GetModuleHandleW", StringMarshalling = StringMarshalling.Utf16)]
+    private static partial nint GetModuleHandle(string? moduleName);
+
     private static bool IsApplicationIdle() => PeekMessage(out _, 0, 0, 0, 0) == 0;
 }