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fix: require live-tree membership for UIElement focusability#23645
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morning4coffe-dev wants to merge 1 commit into
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fix: require live-tree membership for UIElement focusability#23645morning4coffe-dev wants to merge 1 commit into
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WinUI's CUIElement::IsFocusable requires IsActive() (element in the live visual tree), but Uno's port had that check commented out. This let Focus() and FindFirstFocusableElement succeed against detached elements, so a stale deferred focus call (e.g. from app code reacting to a view that already left the tree) could steal focus out of a TabFocusNavigation="Cycle" scope with no way back in. Add IsActiveOrAttachedUnderActiveAncestor(), checked under __CROSSRUNTIME__ in UIElement.IsFocusable and Hyperlink.IsFocusable. The ancestor walk (not a bare IsActiveInVisualTree check) is required because Uno's enhanced lifecycle activates freshly attached children one tick after they get a live parent, while WinUI enters them synchronously - a bare check regresses same-tick focus scenarios like a ComboBox focusing its item container right when the dropdown opens.
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Pull request overview
This PR aligns Uno’s focusability behavior with WinUI by requiring live-tree membership (or being newly attached under an active ancestor) for an element to be considered focusable on crossruntime targets, preventing detached elements from stealing focus or being returned by focus-candidate searches.
Changes:
- Gate
UIElement.IsFocusablewith a new crossruntime live-tree check (IsActiveOrAttachedUnderActiveAncestor()). - Apply the same live-tree gating to
Hyperlink.IsFocusable()via the containingFrameworkElement. - Add runtime tests covering focus and focus-candidate behavior for detached subtrees, including a
TabFocusNavigation=Cycleregression scenario.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/Uno.UI/UI/Xaml/UIElement.FocusMixins.cs | Adds crossruntime live-tree/active-ancestor gating to IsFocusable and introduces IsActiveOrAttachedUnderActiveAncestor(). |
| src/Uno.UI/UI/Xaml/Documents/Hyperlink.mux.cs | Ensures hyperlinks respect the same crossruntime live-tree focusability rules via the containing element. |
| src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Input/Given_FocusManager_DetachedElements.cs | Adds WinUI-parity runtime tests validating focus behavior for detached elements/subtrees and tab-cycling scope integrity. |
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GitHub Issue: closes #
PR Type:
🐞 Bugfix
What changed? 🚀
TEMP, looking into implementing is active.
WinUI's CUIElement::IsFocusable requires IsActive() (element in the live visual tree), but Uno's port had that check commented out. This let Focus() and FindFirstFocusableElement succeed against detached elements, so a stale deferred focus call (e.g. from app code reacting to a view that already left the tree) could steal focus out of a TabFocusNavigation="Cycle" scope with no way back in.
Add IsActiveOrAttachedUnderActiveAncestor(), checked under CROSSRUNTIME in UIElement.IsFocusable and Hyperlink.IsFocusable. The ancestor walk (not a bare IsActiveInVisualTree check) is required because Uno's enhanced lifecycle activates freshly attached children one tick after they get a live parent, while WinUI enters them synchronously - a bare check regresses same-tick focus scenarios like a ComboBox focusing its item container right when the dropdown opens.
PR Checklist ✅
Screenshots Compare Test Runresults.