Simplify glyph cache initialization

Author: codymullins

src/ImageSharp.Drawing/Processing/DrawingCanvas{TPixel}.cs

@@ -62,8 +62,8 @@ public sealed class DrawingCanvas<TPixel> : DrawingCanvas
     // Per-canvas glyph-outline cache: hoists RichTextGlyphRenderer's per-glyph outline cache from
     // per-DrawText-call scope up to the whole canvas, so a glyph outline built once is reused by
     // every DrawText call on this canvas (across a frame's many text runs) instead of being
-    // rebuilt for every run on a text-heavy page. Lazily created on first text draw.
-    private Dictionary<RichTextGlyphRenderer.CacheKey, List<RichTextGlyphRenderer.GlyphRenderData>>? glyphCache;
+    // rebuilt for every run on a text-heavy page.
+    private readonly Dictionary<RichTextGlyphRenderer.CacheKey, List<RichTextGlyphRenderer.GlyphRenderData>> glyphCache = [];
 
     /// <summary>
     /// Initializes a new instance of the <see cref="DrawingCanvas{TPixel}"/> class.
@@ -443,10 +443,6 @@ public override void DrawText(
         this.DrawTextCore(textOptions, text, path, brush, pen);
     }
 
-    // Returns the per-canvas glyph-outline cache, lazily creating it on first use.
-    private Dictionary<RichTextGlyphRenderer.CacheKey, List<RichTextGlyphRenderer.GlyphRenderData>> ResolveGlyphCache()
-        => this.glyphCache ??= [];
-
     private void DrawTextCore(
         RichTextOptions textOptions,
         ReadOnlySpan<char> text,
@@ -467,7 +463,7 @@ private void DrawTextCore(
         EnsureTextPaint(brush, pen);
 
         RichTextOptions configuredOptions = ConfigureTextOptions(textOptions, path, out IPath? configuredPath);
-        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, configuredPath, pen, brush, this.ResolveGlyphCache());
+        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, configuredPath, pen, brush, this.glyphCache);
         TextRenderer renderer = new(glyphRenderer);
         renderer.RenderText(text, configuredOptions);
 
@@ -497,7 +493,7 @@ public override void DrawText(
             effectiveOptions.ShapeOptions,
             Matrix4x4.CreateTranslation(location.X, location.Y, 0) * effectiveOptions.Transform);
 
-        using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.ResolveGlyphCache());
+        using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.glyphCache);
         textBlock.RenderTo(glyphRenderer, wrappingLength);
 
         this.DrawTextOperations(glyphRenderer.DrawingOperations, placedOptions, state.ClipPaths);
@@ -519,7 +515,7 @@ public override void DrawText(
         DrawingCanvasState state = this.ResolveState();
         DrawingOptions effectiveOptions = state.Options;
 
-        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.ResolveGlyphCache());
+        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.glyphCache);
         textBlock.RenderTo(glyphRenderer, wrappingLength);
 
         this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions, state.ClipPaths);
@@ -547,7 +543,7 @@ public override void DrawText(
             effectiveOptions.ShapeOptions,
             Matrix4x4.CreateTranslation(location.X, location.Y, 0) * effectiveOptions.Transform);
 
-        using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.ResolveGlyphCache());
+        using RichTextGlyphRenderer glyphRenderer = new(placedOptions, path: null, pen, brush, this.glyphCache);
         lineLayout.RenderTo(glyphRenderer);
 
         this.DrawTextOperations(glyphRenderer.DrawingOperations, placedOptions, state.ClipPaths);
@@ -568,7 +564,7 @@ public override void DrawText(
         DrawingCanvasState state = this.ResolveState();
         DrawingOptions effectiveOptions = state.Options;
 
-        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.ResolveGlyphCache());
+        using RichTextGlyphRenderer glyphRenderer = new(effectiveOptions, path, pen, brush, this.glyphCache);
         lineLayout.RenderTo(glyphRenderer);
 
         this.DrawTextOperations(glyphRenderer.DrawingOperations, effectiveOptions, state.ClipPaths);
@@ -1155,7 +1151,7 @@ public override void Dispose()
             }
 
             // Release the per-canvas glyph-outline cache.
-            this.glyphCache = null;
+            this.glyphCache.Clear();
 
             this.isDisposed = true;
         }