Fix RenderTargetBitmap looses effects

[timunie]

What does the pull request do?

RTB currently does not render effects such as BoxShadow. This is caused by immediate renderer which has no API for it.

What is the current behavior?

Effects are excluded from the RTB

What is the updated/expected behavior with this PR?

RTB can also save effects

How was the solution implemented (if it's not obvious)?

Added the needed Push / Pop-Effect methods

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

this adds Effect as a new API member

Obsoletions / Deprecations

Fixed issues

Fixes #20779
Fixes #19519 (cc @evanchen6185 if you want to add some feedback on this topic)

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0062807-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Copilot]

Pull request overview

Fixes missing effect rendering (e.g., DropShadowEffect/BoxShadow) when rendering via RenderTargetBitmap.Render by introducing effect push/pop support in DrawingContext implementations and wiring effects into the immediate renderer/recording paths.

Changes:

• Added DrawingContext.PushEffect(...) / PopEffectCore() plumbing across platform and composition drawing contexts.
• Updated ImmediateRenderer to apply Visual.Effect during immediate (RTB) rendering.
• Added/updated Skia render tests + expected PNGs to cover RTB effects and DrawingGroup effects.

Reviewed changes

Copilot reviewed 9 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Avalonia.Base/Media/DrawingContext.cs	Adds public PushEffect + new abstract core methods and restore-state handling.
src/Avalonia.Base/Rendering/ImmediateRenderer.cs	Pushes Visual.Effect during immediate tree traversal.
src/Avalonia.Base/Media/PlatformDrawingContext.cs	Implements effect push/pop for platform contexts that support effects.
src/Avalonia.Base/Rendering/Composition/Drawing/RenderDataDrawingContext.cs	Records effect nodes into composition render data.
src/Avalonia.Base/Rendering/Composition/Drawing/Nodes/RenderDataNodes.cs	Adds a render-data node to push/pop effects at playback time.
src/Avalonia.Base/Media/DrawingGroup.cs	Adds Effect property and records effect pushes when building drawing groups.
tests/Avalonia.RenderTests/Media/RenderTargetBitmapTests.cs	Adds RTB regression test for DropShadow rendering.
tests/Avalonia.RenderTests/Media/DrawingContextTests.cs	Adds render test for DrawingGroup with an effect push.
tests/Avalonia.Controls.UnitTests/Shapes/ShapeTests.cs	Updates test drawing context stub for new abstract methods.
tests/TestFiles/.../*.expected.png	Adds/updates expected outputs for new effect rendering behavior.

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[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0062839-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

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[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0063040-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 12 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

src/Avalonia.Base/Rendering/ImmediateRenderer.cs:73

• ImmediateRenderer still uses visualBounds = rect.TransformToAABB(totalTransform) for culling, which ignores the extra pixels produced by visual.Effect (blur/drop shadow). This can cause a visual to be skipped entirely when its original bounds are outside clipRect but its effect output would intersect it. Consider inflating rect (or visualBounds) by effect.GetEffectOutputPadding() before the intersection test, similar to how compositor subtree bounds are inflated for effects.

            var totalTransform = transform * parentTransform;
            var visualBounds = rect.TransformToAABB(totalTransform);

            if (visualBounds.Intersects(clipRect))
            {
                visual.Render(context);

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[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0063090-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[Copilot]

Pull request overview

Copilot reviewed 10 out of 12 changed files in this pull request and generated 1 comment.

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