[Windows] Fixed CanvasDrawingSession Exception on Clipping Image #30028
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Pull Request Overview
This PR fixes a Windows-only CanvasDrawingSessionException by resetting the canvas state after each draw, and adds a full repro via HostApp and automated tests.
- Adds
_canvas.ResetState()inOnDrawto ensure the canvas is cleared after drawing. - Introduces a new UI page (
Issue18430) with clipping drawable and embeds the required image resource. - Adds shared and host-app test cases to validate that no exception is thrown.
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/Graphics/src/Graphics/Platforms/Windows/PlatformGraphicsView.cs | Call ResetState() after drawing to clear state |
| src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue18430.cs | New shared UI test checking that the page loads |
| src/Controls/tests/TestCases.HostApp/Issues/Issue18430.cs | HostApp page and clipping drawable for repro |
| src/Controls/tests/TestCases.HostApp/Controls.TestCases.HostApp.csproj | Embed royals.png so the drawable can load the image |
Comment on lines
88
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92
| _canvas.Session = args.DrawingSession; | ||
| _canvas.CanvasSize = new global::Windows.Foundation.Size(_dirty.Width, _dirty.Height); | ||
| _drawable.Draw(_canvas, _dirty); | ||
| _canvas.ResetState(); | ||
| PlatformGraphicsService.ThreadLocalCreator = null; |
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Consider wrapping the draw logic (setting session, size, and calling Draw) and the ResetState call in a try/finally block so that the canvas state is always reset even if _drawable.Draw(...) throws an exception.
Suggested change
| _canvas.Session = args.DrawingSession; | |
| _canvas.CanvasSize = new global::Windows.Foundation.Size(_dirty.Width, _dirty.Height); | |
| _drawable.Draw(_canvas, _dirty); | |
| _canvas.ResetState(); | |
| PlatformGraphicsService.ThreadLocalCreator = null; | |
| try | |
| { | |
| _canvas.Session = args.DrawingSession; | |
| _canvas.CanvasSize = new global::Windows.Foundation.Size(_dirty.Width, _dirty.Height); | |
| _drawable.Draw(_canvas, _dirty); | |
| } | |
| finally | |
| { | |
| _canvas.ResetState(); | |
| PlatformGraphicsService.ThreadLocalCreator = null; | |
| } |
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I think the suggestion is correct.
sheiksyedm
added
platform/windows
area-drawing
jsuarezruiz
requested changes
Jun 18, 2025
Comment on lines
88
to
92
| _canvas.Session = args.DrawingSession; | ||
| _canvas.CanvasSize = new global::Windows.Foundation.Size(_dirty.Width, _dirty.Height); | ||
| _drawable.Draw(_canvas, _dirty); | ||
| _canvas.ResetState(); | ||
| PlatformGraphicsService.ThreadLocalCreator = null; |
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I think the suggestion is correct.
|
@jsuarezruiz I have modified the suggested changes |
|
/azp run |
|
Azure Pipelines successfully started running 3 pipeline(s). |
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Note
Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!
Root Cause
The exception CanvasDrawingSessionException occurred because the Canvas state was not reset after drawing
Description of Change
Added a call to _canvas.ResetState() in the OnDraw method to ensure the canvas state is properly reset after drawing.
Tested the behavior in the following platforms:
Issues Fixed
Fixes #18430
Screenshot