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Release the TextBlock text layout when the control is detached - #22281
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Gillibald merged 1 commit intoOct 5, 2026
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MrJul
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LGTM
Thanks for the contribution
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What does the pull request do?
TextBlockkeeps itsTextLayoutalive after it has been detached from the visual tree, whenever the layout was built while the measure was already invalid.What is the current behavior?
TextLayoutis only released fromOnMeasureInvalidated.InvalidateMeasureraises that override only while the measure is still valid, so once the measure has been invalidated the control holds its layout (and the native resources it owns) until the next measure pass.A render pass reads
TextBlock.TextLayout, which materializes the layout lazily. Reading it between an invalidation and the next measure pass therefore leaves the control holding a layout that nothing will release. If the control is then removed from the tree, the layout is never disposed.What is the updated/expected behavior with this PR?
The layout is released when the control leaves the visual tree, regardless of the state of its measure.
TextLayoutis materialized lazily, so a control that is attached again rebuilds it on the next measure or render pass.How was the solution implemented (if it's not obvious)?
OnDetachedFromVisualTreecalls the existingDisposeTextLayout, which is unconditional.Three tests were added:
Detaching_Should_Release_TextLayoutthe case that already passes today, kept so the two paths are visible side by side.Detaching_Should_Release_TextLayout_Built_While_Measure_Is_Invalidthe failing case. It is the only test inAvalonia.Controls.UnitTeststhat fails without the fix (1 of 3966).Reattaching_Should_Rebuild_TextLayouta regression guard for disposing on detach. It passes with and without the fix; it is there to catch a control left blank after being reattached.The tests observe the layout through a new
internal bool HasTextLayout, following the existinginternal bool HasComplexContent, rather than through reflection.Checklist
Breaking changes
None
Obsoletions / Deprecations
None
Fixed issues
None