Avoid state sharing (#18)

README.md

@@ -95,6 +95,10 @@ This library is also used in production by [KnowledgePicker](https://knowledgepi
 
 As mentioned [above](#how-to-use), only subset of functionality is implemented now, but all contributions are welcome. Feel free to open [issues](https://github.com/knowledgepicker/word-cloud/issues) and [pull requests](https://github.com/knowledgepicker/word-cloud/pulls).
 
+### Testing
+
+Tests are currently only supported on Linux, because they are snapshot tests (generating a word cloud image and comparing it byte-by-byte with a snapshot) and more work is needed to ensure this is cross-platform (e.g., use exactly the same font). On Windows, tests can be run in WSL (Visual Studio supports this directly). Tests are also automatically run in GitHub Actions.
+
 ### Release process
 
 After pushing a tag, GitHub workflow `release.yml` is triggered which builds and publishes the NuGet package.

src/KnowledgePicker.WordCloud/Drawing/IGraphicEngine.cs

@@ -35,5 +35,7 @@ public interface IGraphicEngine : IDisposable
  public interface IGraphicEngine<TBitmap> : IGraphicEngine
  {
  TBitmap Bitmap { get; }
+
+ IGraphicEngine<TBitmap> Clone();
  }
 }

src/KnowledgePicker.WordCloud/Drawing/SkGraphicEngine.cs

@@ -13,6 +13,16 @@ public sealed class SkGraphicEngine : IGraphicEngine<SKBitmap>
  private readonly SKPaint textPaint;
  private readonly WordCloudInput wordCloud;
 
+ private SkGraphicEngine(ISizer sizer, WordCloudInput wordCloud,
+ SKPaint textPaint)
+ {
+ Sizer = sizer;
+ this.wordCloud = wordCloud;
+ this.textPaint = textPaint;
+ Bitmap = new SKBitmap(wordCloud.Width, wordCloud.Height);
+ canvas = new SKCanvas(Bitmap);
+ }
+
  public SkGraphicEngine(ISizer sizer, WordCloudInput wordCloud,
  SKTypeface? font = null, bool antialias = true)
  {
@@ -52,6 +62,11 @@ public void Draw(PointD location, RectangleD measured, string text, int count, s
  (float)(location.Y - measured.Top), textPaint);
  }
 
+ public IGraphicEngine<SKBitmap> Clone()
+ {
+ return new SkGraphicEngine(Sizer, wordCloud, textPaint);
+ }
+
  public void Dispose()
  {
  textPaint.Dispose();

src/KnowledgePicker.WordCloud/Layouts/BaseLayout.cs

@@ -39,6 +39,8 @@ public IEnumerable<LayoutItem> GetWordsInArea(RectangleD area)
  return QuadTree.Query(area);
  }
 
+ public abstract ILayout Clone();
+
  protected bool IsInsideSurface(RectangleD targetRectangle)
  {
  return IsInside(Surface, targetRectangle);

src/KnowledgePicker.WordCloud/Layouts/ILayout.cs

@@ -11,5 +11,6 @@ public interface ILayout
  {
  int Arrange(IEnumerable<WordCloudEntry> entries, IGraphicEngine engine);
  IEnumerable<LayoutItem> GetWordsInArea(RectangleD area);
+ ILayout Clone();
  }
 }

src/KnowledgePicker.WordCloud/Layouts/SpiralLayout.cs

@@ -40,6 +40,11 @@ public override bool TryFindFreeRectangle(SizeD size, out RectangleD foundRectan
  return false;
  }
 
+ public override ILayout Clone()
+ {
+ return new SpiralLayout(WordCloud);
+ }
+
  private static double GetPseudoRandomStartAngle(SizeD size)
  {
  return size.Height * size.Width;

src/KnowledgePicker.WordCloud/Primitives/LayoutItem.cs

@@ -3,7 +3,7 @@ namespace KnowledgePicker.WordCloud.Primitives
  /// <summary>
  /// Word arranged somewhere in word cloud.
  /// </summary>
- public class LayoutItem
+ public record LayoutItem
  {
  public LayoutItem(WordCloudEntry entry, PointD location, RectangleD measured)
  {

src/KnowledgePicker.WordCloud/WordCloudGenerator.cs

@@ -41,13 +41,19 @@ public WordCloudGenerator(WordCloudInput wordCloud,
  private T Process<T>(
  Func<IGraphicEngine<TBitmap>, IEnumerable<LayoutItem>, T> handler)
  {
+ // Ensure state is not shared.
+ // TODO: We should instead use factory pattern.
+ // But that would be a big change in usage of this class.
+ var localEngine = engine.Clone();
+ var localLayout = layout.Clone();
+
  // Arrange word cloud.
  var size = new SizeD(wordCloud.Width, wordCloud.Height);
- layout.Arrange(wordCloud.Entries, engine);
+ localLayout.Arrange(wordCloud.Entries, localEngine);
 
  // Process results.
  var area = new RectangleD(new PointD(0, 0), size);
- return handler(engine, layout.GetWordsInArea(area));
+ return handler(localEngine, localLayout.GetWordsInArea(area));
  }
 
  public IEnumerable<(LayoutItem Item, double FontSize)> Arrange()

test/KnowledgePicker.WordCloud.Tests/WordCloudGeneratorTests.cs

@@ -0,0 +1,39 @@
+using KnowledgePicker.WordCloud.Drawing;
+using KnowledgePicker.WordCloud.Layouts;
+using KnowledgePicker.WordCloud.Primitives;
+using KnowledgePicker.WordCloud.Sizers;
+using SkiaSharp;
+
+namespace KnowledgePicker.WordCloud.Tests;
+
+public class WordCloudGeneratorTests
+{
+ [Fact] // https://github.com/knowledgepicker/word-cloud/issues/17
+ public void DoesNotShareState()
+ {
+ // Arrange.
+ var wordCloud = new WordCloudInput(new[]
+ {
+ new WordCloudEntry("a", 1),
+ new WordCloudEntry("b", 1),
+ })
+ {
+ Width = 1024,
+ Height = 256,
+ MinFontSize = 8,
+ MaxFontSize = 32
+ };
+ var sizer = new LogSizer(wordCloud);
+ using var engine = new SkGraphicEngine(sizer, wordCloud);
+ var layout = new SpiralLayout(wordCloud);
+ var wcg = new WordCloudGenerator<SKBitmap>(wordCloud, engine, layout);
+
+ // Act.
+ var result1 = wcg.Arrange().ToArray();
+ var result2 = wcg.Arrange().ToArray();
+
+ // Assert.
+ Assert.Equal(result1.AsEnumerable(), result2);
+ Assert.Equal(2, result2.Length);
+ }
+}