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Merged
JimBobSquarePants merged 2 commits into from
Sep 14, 2026
Merged

Make DrawingTextCache thread-safe #420

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1747da0
Make DrawingTextCache thread-safe
JimBobSquarePants Sep 14, 2026
70d94cd
Stabilize concurrent cache tests
JimBobSquarePants Sep 14, 2026
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4 changes: 2 additions & 2 deletions src/ImageSharp.Drawing/ImageSharp.Drawing.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -44,8 +44,8 @@
<InternalsVisibleTo Include="SixLabors.ImageSharp.Drawing.WebGPU" Key="$(SixLaborsPublicKey)" />
</ItemGroup>
<ItemGroup>
<PackageReference Include="SixLabors.Fonts" Version="3.1.0" />
<PackageReference Include="SixLabors.ImageSharp" Version="4.1.0" />
<PackageReference Include="SixLabors.Fonts" Version="3.1.2" />
<PackageReference Include="SixLabors.ImageSharp" Version="4.1.2" />
<PackageReference Include="SixLabors.PolygonClipper" Version="1.0.1" />
</ItemGroup>

Expand Down
72 changes: 23 additions & 49 deletions src/ImageSharp.Drawing/Processing/DrawingCanvas{TPixel}.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,26 +72,6 @@ public sealed class DrawingCanvas<TPixel> : DrawingCanvas
/// </summary>
private readonly DrawingTextCache textCache;

/// <summary>
/// Reusable operation list handed to each text renderer. Hosted by the text cache because
/// canvases are per-frame objects; sharing the cache-owned list keeps its capacity across
/// frames instead of regrowing a fresh list of large operation structs per draw.
/// </summary>
private readonly List<DrawingOperation> textOperations;

/// <summary>
/// Reusable sort buffer for <see cref="DrawTextOperations"/>, hosted by the text cache for
/// the same reason as <see cref="textOperations"/>. Only pass and index pairs are sorted;
/// the operations themselves stay in place so the per-draw sort moves eight bytes per
/// entry instead of the full operation struct.
/// </summary>
private readonly List<(byte RenderPass, int Sequence)> textOperationSortBuffer;

/// <summary>
/// Reusable stack pairing the begin and end commands for nested text composite layers.
/// </summary>
private readonly List<DrawingCanvasLayer> textCompositeLayerStack;

/// <summary>
/// Initializes a new instance of the <see cref="DrawingCanvas{TPixel}"/> class.
/// </summary>
Expand Down Expand Up @@ -303,9 +283,6 @@ private DrawingCanvas(
this.targetFrame = targetFrame;
this.batcher = batcher;
this.textCache = textCache;
this.textOperations = textCache.OperationScratch;
this.textOperationSortBuffer = textCache.OperationSortScratch;
this.textCompositeLayerStack = textCache.CompositeLayerScratch;
this.ownsBatcher = ownsBatcher;
this.ownsTextCache = ownsTextCache;
this.pendingImageResources = pendingImageResources;
Expand Down Expand Up @@ -869,11 +846,11 @@ configuredOptions.VisibleBounds is null &&
};
}

using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, configuredPath, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, configuredPath, pen, brush, this.textCache);
TextRenderer renderer = new(glyphRenderer);
renderer.Render(text, configuredOptions);

this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, effectiveOptions);
}

/// <inheritdoc />
Expand All @@ -900,7 +877,7 @@ public override void DrawText(
Matrix4x4.CreateTranslation(location.X, location.Y, 0) * effectiveOptions.Transform,
effectiveOptions.TextContrast);

using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.textCache);
if (TryGetVisibleTextBounds(state, placedOptions.Transform, out FontRectangle visibleBounds))
{
textBlock.RenderTo(glyphRenderer, wrappingLength, visibleBounds);
Expand All @@ -910,7 +887,7 @@ public override void DrawText(
textBlock.RenderTo(glyphRenderer, wrappingLength);
}

this.DrawTextOperations(glyphRenderer.DrawingOperations, placedOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, placedOptions);
}

/// <inheritdoc />
Expand All @@ -929,10 +906,10 @@ public override void DrawText(
DrawingCanvasState state = this.ResolveState();
DrawingOptions effectiveOptions = state.Options;

using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.textCache);
textBlock.RenderTo(glyphRenderer, wrappingLength);

this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, effectiveOptions);
}

/// <inheritdoc />
Expand All @@ -958,10 +935,10 @@ public override void DrawText(
Matrix4x4.CreateTranslation(location.X, location.Y, 0) * effectiveOptions.Transform,
effectiveOptions.TextContrast);

using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.textCache);
lineLayout.RenderTo(glyphRenderer);

this.DrawTextOperations(glyphRenderer.DrawingOperations, placedOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, placedOptions);
}

/// <inheritdoc />
Expand All @@ -979,10 +956,10 @@ public override void DrawText(
DrawingCanvasState state = this.ResolveState();
DrawingOptions effectiveOptions = state.Options;

using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.textCache);
lineLayout.RenderTo(glyphRenderer);

this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, effectiveOptions);
}

/// <inheritdoc />
Expand All @@ -999,11 +976,11 @@ public override void DrawText(
DrawingCanvasState state = this.ResolveState();
DrawingOptions effectiveOptions = state.Options;

using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path: null, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path: null, pen, brush, this.textCache);
TextRenderer renderer = new(glyphRenderer);
renderer.Render(glyphId, options);

this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions);
this.DrawTextOperations(glyphRenderer.DrawingOperations, glyphRenderer.Scratch, effectiveOptions);
}

/// <inheritdoc />
Expand All @@ -1023,11 +1000,11 @@ public override void DrawText(ReadOnlySpan<ushort> glyphIds, ReadOnlySpan<Vector
DrawingCanvasState state = this.ResolveState();
DrawingOptions effectiveOptions = state.Options;

using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path: null, pen, brush, this.textCache, this.textOperations);
using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path: null, pen, brush, this.textCache);
TextRenderer renderer = new(glyphRenderer);
renderer.Render(glyphIds, points, options);

this.DrawTextOperations(this.BatchGlyphRunOperations(glyphRenderer.DrawingOperations), effectiveOptions);
this.DrawTextOperations(this.BatchGlyphRunOperations(glyphRenderer.DrawingOperations), glyphRenderer.Scratch, effectiveOptions);
}

/// <inheritdoc />
Expand Down Expand Up @@ -1801,17 +1778,20 @@ private static IPath GetPositionedGlyphPath(DrawingTextCache.RunPathCacheEntry e
/// Converts rendered text operations to composition commands and submits them to the batcher.
/// </summary>
/// <param name="operations">Text drawing operations produced by glyph layout/rendering.</param>
/// <param name="scratch">The working buffers leased by this draw's renderer.</param>
/// <param name="drawingOptions">Drawing options applied to each operation.</param>
private void DrawTextOperations(List<DrawingOperation> operations, DrawingOptions drawingOptions)
private void DrawTextOperations(
List<DrawingOperation> operations,
DrawingTextCache.DrawingScratch scratch,
DrawingOptions drawingOptions)
{
// Enforce render-pass ordering while preserving original emission order inside each
// pass. This preserves overlapping color-font layer compositing semantics (for
// example emoji mouth/teeth layers) and keeps the composite group markers paired
// with the fill operations they contain.
// The cache-owned buffer keeps its capacity across draws; draw calls never overlap on
// one canvas.
List<(byte RenderPass, int Sequence)> entries = this.textOperationSortBuffer;
entries.Clear();
// The renderer leases these buffers until command submission completes. Other canvases
// sharing the cache rent different buffers, while sequential draws retain capacity.
List<(byte RenderPass, int Sequence)> entries = scratch.SortBuffer;

// Queued glyph commands never carry the canvas transform: glyph geometry arrives with
// it already applied, and the sub-pixel remainder rides the command itself. One shared
Expand All @@ -1832,8 +1812,7 @@ private void DrawTextOperations(List<DrawingOperation> operations, DrawingOption
return cmp != 0 ? cmp : a.Sequence.CompareTo(b.Sequence);
});

List<DrawingCanvasLayer> compositeLayers = this.textCompositeLayerStack;
compositeLayers.Clear();
List<DrawingCanvasLayer> compositeLayers = scratch.CompositeLayers;
DrawingCanvasState state = this.ResolveState();

for (int i = 0; i < entries.Count; i++)
Expand Down Expand Up @@ -1879,11 +1858,6 @@ private void DrawTextOperations(List<DrawingOperation> operations, DrawingOption
this.batcher.AddStrokePath(((StrokePathCompositionSceneCommand)command).Command);
}
}

// The buffers outlive the canvas (the text cache hosts them), so drop the layer
// references now rather than rooting the final draw's state until the next draw.
entries.Clear();
compositeLayers.Clear();
}

/// <summary>
Expand Down
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