Use SkiaSharp instead of WPF to render theme previews #672

t1m0thyj · 2025-11-18T11:43:19Z

Advantages:

Smaller binaries (by ~15 MB) and memory footprint
Can achieve higher refresh rate for animation (120 fps)

Disadvantages:

More complex code to manually render UI elements

Added security-extended queries to CodeQL initialization.

Copilot

Pull request overview

This PR migrates the theme preview rendering from WPF to SkiaSharp, aiming to reduce binary size by ~15 MB and enable higher animation refresh rates (120 fps). The migration removes WPF dependencies and replaces XAML-based UI with manual rendering code using SkiaSharp's canvas API.

Key changes:

Replaced WPF ThemePreviewer UserControl with SkiaSharp-based SKControl implementation
Implemented manual UI rendering in ThemePreviewRenderer for overlays, buttons, and animations
Created ImageCache to manage SkiaSharp image resources with thread-safe caching
Removed WPF dependencies from project configuration and replaced System.Windows.Rect with custom RECT struct

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 22 comments.

Show a summary per file

File	Description
src/WinDynamicDesktop.csproj	Removed WPF dependency, added SkiaSharp packages (v3.119.1), changed font resource from Resource to EmbeddedResource, added MSBuild target to exclude OpenTK/glfw3 from single-file bundle
src/WPF/ThemePreviewer.xaml.cs	Deleted - WPF code-behind for theme previewer user control
src/WPF/ThemePreviewer.xaml	Deleted - XAML markup defining WPF-based theme preview UI
src/WPF/RelayCommand.cs	Deleted - WPF ICommand implementation no longer needed
src/WPF/BitmapCache.cs	Deleted - WPF BitmapImage cache replaced by SkiaSharp ImageCache
src/ThemeDialog.cs	Updated to use new Skia.ThemePreviewer instead of WPF ThemePreviewer, removed ElementHost initialization
src/ThemeDialog.Designer.cs	Changed previewerHost type from ElementHost to Skia.ThemePreviewer
src/Skia/ThemePreviewerViewModel.cs	Refactored from WPF namespace to Skia, replaced BitmapImage with SKImage, changed from WPF DispatcherTimer to Windows Forms Timer, removed ICommand dependencies, added public methods for UI interactions
src/Skia/ThemePreviewer.cs	New SkiaSharp-based control inheriting from SKControl, implements 120 FPS animations using Forms Timer, handles mouse/keyboard input, manages FontAwesome font loading
src/Skia/ThemePreviewRenderer.cs	New renderer class handling all manual drawing of UI elements (images, overlays, buttons, text) using SkiaSharp canvas APIs
src/Skia/ImageCache.cs	New thread-safe image cache for SkiaSharp SKImage resources with decode size limiting and explicit disposal
src/COM/DesktopWallpaper.cs	Added RECT struct definition and changed GetMonitorRECT return type from System.Windows.Rect to custom RECT to remove WPF dependency
.github/workflows/codeql.yml	Added .NET setup step with version 10.0.x and security-extended queries

Files not reviewed (1)

src/ThemeDialog.Designer.cs: Language not supported

Comments suppressed due to low confidence (7)

src/Skia/ThemePreviewerViewModel.cs:386

[nitpick] Potential memory leak: BackImage and FrontImage SKImage objects are set to null without being disposed. Since these are references to images from the cache, and the cache handles disposal in Clear(), this is okay. However, for clarity and to follow best practices, consider adding a comment explaining that these images are owned by the cache and will be disposed there.
src/Skia/ThemePreviewer.cs:51
Write to static field from instance method, property, or constructor.

                    fontAwesome = SKTypeface.FromStream(fontStream);

src/Skia/ThemePreviewerViewModel.cs:447

Poor error handling: empty catch block.
src/Skia/ThemePreviewerViewModel.cs:399
Local scope variable 'previewText' shadows ThemePreviewerViewModel.previewText.
src/Skia/ThemePreviewerViewModel.cs:227
Local scope variable 'downloadAction' shadows ThemePreviewerViewModel.downloadAction.
src/Skia/ThemePreviewerViewModel.cs:399
This assignment to previewText is useless, since its value is never read.
src/Skia/ThemePreviewerViewModel.cs:36
Both branches of this 'if' statement write to the same variable - consider using '?' to express intent better.

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Copilot · 2025-11-30T05:01:24Z

src/Skia/ImageCache.cs

+                                    var image = SKImage.FromBitmap(scaledBitmap);
+                                    return image;


Missing null check after SKImage.FromBitmap() calls. If the bitmap conversion fails, this could return null but the code doesn't handle this case. Consider adding null checks before returning the image, or use a guard clause to ensure the image is not null before adding it to the cache.

Copilot · 2025-11-30T05:01:25Z

src/Skia/ImageCache.cs

+                                var image = SKImage.FromBitmap(sourceBitmap);
+                                return image;


Missing null check after SKImage.FromBitmap() call. If the bitmap conversion fails, this could return null but the code doesn't handle this case. Consider adding a null check before returning the image.

Copilot · 2025-11-30T05:01:25Z

src/Skia/ThemePreviewer.cs

+            if (fontAwesome == null)
+            {
+                using (Stream fontStream = Assembly.GetExecutingAssembly()
+                    .GetManifestResourceStream("WinDynamicDesktop.resources.fonts.fontawesome-webfont.ttf"))
+                {
+                    fontAwesome = SKTypeface.FromStream(fontStream);


[nitpick] The static fontAwesome SKTypeface is never disposed. Since it's loaded once and kept for the lifetime of the application, it should be properly disposed when the application terminates. Consider implementing IDisposable on a static manager class or ensuring proper cleanup. This could lead to a resource leak, though it may be acceptable if it's truly application-lifetime.

Copilot · 2025-11-30T05:01:25Z

src/Skia/ThemePreviewRenderer.cs

+            titleFont = new SKFont(SKTypeface.FromFamilyName("Segoe UI", SKFontStyleWeight.Bold, SKFontStyleWidth.Normal, SKFontStyleSlant.Upright), 19);
+            previewFont = new SKFont(SKTypeface.FromFamilyName("Segoe UI", SKFontStyleWeight.Normal, SKFontStyleWidth.Normal, SKFontStyleSlant.Upright), 16);
+            textFont = new SKFont(SKTypeface.FromFamilyName("Segoe UI"), 16);
+            iconFont16 = new SKFont(fontAwesome, 16);
+            iconFont20 = new SKFont(fontAwesome, 20);


The SKTypeface objects created from FromFamilyName() should be stored as fields and properly disposed. Currently, they are created inline and passed to SKFont constructors. The SKFont.Dispose() will not dispose the underlying typeface. Store these typefaces as fields and dispose them in the Dispose method to prevent resource leaks.

Copilot · 2025-11-30T05:01:26Z

src/WinDynamicDesktop.csproj

-</Project>
+  <Target Name="ExplicitRemoveFromFilesToBundle" BeforeTargets="GenerateSingleFileBundle" DependsOnTargets="PrepareForBundle">
+    <ItemGroup>
+      <FilesToRemoveFromBundle Include="@(FilesToBundle)" Condition="($([System.String]::Copy('%(Filename)').StartsWith('OpenTK'))) OR ('%(Filename)' == 'glfw3')" />


[nitpick] The MSBuild target filtering condition uses string operations that may not work as expected. The condition $([System.String]::Copy('%(Filename)').StartsWith('OpenTK')) creates an unnecessary copy. Consider simplifying to '%(Filename)'.StartsWith('OpenTK') or use a more standard MSBuild pattern like @(FilesToBundle->WithMetadataValue('Filename', 'OpenTK*')).

Suggested change

<FilesToRemoveFromBundle Include="@(FilesToBundle)" Condition="($([System.String]::Copy('%(Filename)').StartsWith('OpenTK'))) OR ('%(Filename)' == 'glfw3')" />

<FilesToRemoveFromBundle Include="@(FilesToBundle->WithMetadataValue('Filename', 'OpenTK*'))" />

Copilot · 2025-11-30T05:01:30Z

src/Skia/ThemePreviewRenderer.cs

+            // Title and preview text box (top left)
+            var titleBounds = new SKRect();
+            titleFont.MeasureText(viewModel.Title ?? "", out titleBounds);
+            var previewBounds = new SKRect();


This assignment to previewBounds is useless, since its value is never read.

Copilot · 2025-11-30T05:01:30Z

src/Skia/ThemePreviewRenderer.cs

+            float playOpacity = hoveredItem == ThemePreviewer.HoveredItem.PlayButton ? OPACITY_HOVER : OPACITY_NORMAL;
+            basePaint.Color = SKColors.White.WithAlpha((byte)(255 * playOpacity));
+            string playIcon = viewModel.IsPlaying ? "\uf04c" : "\uf04b";
+            var textBounds = new SKRect();


This assignment to textBounds is useless, since its value is never read.

Suggested change

var textBounds = new SKRect();

SKRect textBounds;

Copilot · 2025-11-30T05:01:30Z

src/Skia/ThemePreviewRenderer.cs

+            // Download message (centered bottom)
+            if (!string.IsNullOrEmpty(viewModel.Message))
+            {
+                var msgBounds = new SKRect();


This assignment to msgBounds is useless, since its value is never read.

Copilot · 2025-11-30T05:01:30Z

src/Skia/ThemePreviewRenderer.cs

+            basePaint.Color = SKColors.White.WithAlpha((byte)(255 * opacity));
+
+            string icon = side == Side.Left ? "\uf053" : "\uf054";
+            var textBounds = new SKRect();


This assignment to textBounds is useless, since its value is never read.

Copilot · 2025-11-30T05:01:31Z

src/Skia/ThemePreviewRenderer.cs

+                return;
+            }
+
+            var textBounds = new SKRect();


This assignment to textBounds is useless, since its value is never read.

t1m0thyj added 6 commits November 17, 2025 22:36

Try replacing WPF with SkiaSharp

21b0f6b

Optimize Skia rendering for 120 fps

fceba51

Remove WPF renderer code

dae9c55

Improve hitbox testing for theme previewer

1b7289d

Cache images rather than bitmaps

abd58ca

Remove unnecessary OpenGL DLLs from publish output

960a9fe

t1m0thyj force-pushed the feat/replace-wpf-with-skia branch 3 times, most recently from c0a9ee5 to 34a90ab Compare November 20, 2025 04:40

Try another method to remove OpenGL DLLs

54d5a49

t1m0thyj force-pushed the feat/replace-wpf-with-skia branch from 34a90ab to 54d5a49 Compare November 20, 2025 04:41

t1m0thyj added 2 commits November 21, 2025 21:24

Update CodeQL workflow to include .NET setup

42f6c84

Update CodeQL workflow to include security queries

522f679

Added security-extended queries to CodeQL initialization.

t1m0thyj marked this pull request as ready for review November 22, 2025 05:29

t1m0thyj added 3 commits November 22, 2025 14:28

Refactor Skia code to use constants and dispose resources

e211b45

Handle mouse leave event for theme previewer

72902bd

Extract rendering code into ThemePreviewRenderer

ba21f1f

t1m0thyj force-pushed the feat/replace-wpf-with-skia branch from caf4450 to ba21f1f Compare November 29, 2025 03:39

t1m0thyj added 2 commits November 29, 2025 10:07

Refactor drawing methods to be more clear

1de9db9

Use linq methods in ThemePreviewer

d82463d

t1m0thyj force-pushed the feat/replace-wpf-with-skia branch from c2fbd4b to d82463d Compare November 30, 2025 04:54

t1m0thyj requested a review from Copilot November 30, 2025 04:55

Copilot started reviewing on behalf of t1m0thyj November 30, 2025 04:55 View session

Copilot finished reviewing on behalf of t1m0thyj November 30, 2025 04:59

Copilot AI reviewed Nov 30, 2025

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Use SkiaSharp instead of WPF to render theme previews #672

Use SkiaSharp instead of WPF to render theme previews #672

t1m0thyj commented Nov 18, 2025 •

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	<FilesToRemoveFromBundle Include="@(FilesToBundle)" Condition="($([System.String]::Copy('%(Filename)').StartsWith('OpenTK'))) OR ('%(Filename)' == 'glfw3')" />
	<FilesToRemoveFromBundle Include="@(FilesToBundle->WithMetadataValue('Filename', 'OpenTK*'))" />

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t1m0thyj commented Nov 18, 2025 •

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