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Fix ArgumentNullException in chrome hit test after window close - #22409
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@cla-avalonia come on, say something |
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@cla-avalonia agree |
MrJul
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backport-candidate-12.1.x
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Meanwhile, this PR is a good fix. |
MrJul
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Oct 9, 2026
* Add failing test for chrome hit test on a closed window * Return null from chrome hit test once the root visual is cleared
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What does the pull request do?
Makes
PresentationSource.HitTestChromeElementreturnnullonceRootVisualhas been cleared byTopLevel.HandleClosed().What is the current behavior?
A closed window with an extended client area can still receive
WM_NCHITTESTand other non-client messages.WindowImpl.HitTestVisualpasses them toHitTestChromeElement, which dereferences the nullRootVisualand throwsArgumentNullExceptioninside the window procedure, so the process terminates.What is the updated/expected behavior with this PR?
A closed window reports no chrome element and the non-client hit test falls back to the regular result.
How was the solution implemented (if it's not obvious)?
The check is in
PresentationSourcerather than in the Win32WindowImpl, so the X11 and Wayland callers are covered too. Both already treatnullas "no chrome element".I ran the repro from the issue on Windows 11 with each
WindowDecorationsvalue, closing the window both withClose()and withSC_CLOSE. Before the change every window with an extended client area crashed the process (0xC000041D); after it the non-client messages are handled normally. Hit-test results on open windows are the same before and after.Checklist
Breaking changes
None.
Fixed issues
Fixes #22324