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Add declarative IsHitTestVisible(bool) common element modifier #810

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Add declarative IsHitTestVisible(bool) common element modifier #810

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2 changes: 2 additions & 0 deletions plugins/reactor/skills/reactor-dsl/references/reactor.api.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -608,6 +608,7 @@ T.Immediate<T>() → T
T.InteractionStates<T>(Func<InteractionStatesBuilder, InteractionStatesBuilder> configure, Curve curve = null) → T
T.IsDragRegion<T>(bool? isDragRegion = true) → T
T.IsEnabled<T>(bool enabled = true) → T
T.IsHitTestVisible<T>(bool isHitTestVisible = true) → T
T.IsTabStop<T>(bool isTabStop = true) → T
T.IsVisible<T>(bool isVisible) → T
T.ItemContainerTransitions<T>(Transition[] transitions) → T
Expand Down Expand Up @@ -2979,6 +2980,7 @@ VisualModifiers Visual { get; init; }
XYFocusKeyboardNavigationMode? XYFocusKeyboardNavigation { get; init; }
bool? IsDragRegion { get; init; }
bool? IsEnabled { get; init; }
bool? IsHitTestVisible { get; init; }
bool? IsTabStop { get; init; }
bool? IsVisible { get; init; }
double? FontSize { get; init; }
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2 changes: 2 additions & 0 deletions skills/reactor.api.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -608,6 +608,7 @@ T.Immediate<T>() → T
T.InteractionStates<T>(Func<InteractionStatesBuilder, InteractionStatesBuilder> configure, Curve curve = null) → T
T.IsDragRegion<T>(bool? isDragRegion = true) → T
T.IsEnabled<T>(bool enabled = true) → T
T.IsHitTestVisible<T>(bool isHitTestVisible = true) → T
T.IsTabStop<T>(bool isTabStop = true) → T
T.IsVisible<T>(bool isVisible) → T
T.ItemContainerTransitions<T>(Transition[] transitions) → T
Expand Down Expand Up @@ -2979,6 +2980,7 @@ VisualModifiers Visual { get; init; }
XYFocusKeyboardNavigationMode? XYFocusKeyboardNavigation { get; init; }
bool? IsDragRegion { get; init; }
bool? IsEnabled { get; init; }
bool? IsHitTestVisible { get; init; }
bool? IsTabStop { get; init; }
bool? IsVisible { get; init; }
double? FontSize { get; init; }
Expand Down
3 changes: 3 additions & 0 deletions src/Reactor/Core/Element.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1191,6 +1191,7 @@ internal static bool ModifiersEqual(ElementModifiers? a, ElementModifiers? b)
&& a.HeadingLevel == b.HeadingLevel
&& a.IsDragRegion == b.IsDragRegion
&& a.IsTabStop == b.IsTabStop
&& a.IsHitTestVisible == b.IsHitTestVisible
&& a.TabIndex == b.TabIndex
&& a.AccessKey == b.AccessKey
&& ReferenceEquals(a.XYFocusUpRef, b.XYFocusUpRef)
Expand Down Expand Up @@ -1997,6 +1998,7 @@ public ElementTheme? RequestedTheme
// ── Accessibility — Tier 1 (inline, commonly needed for WCAG AA) ─
public Microsoft.UI.Xaml.Automation.Peers.AutomationHeadingLevel? HeadingLevel { get; init; }
public bool? IsTabStop { get; init; }
public bool? IsHitTestVisible { get; init; }
public int? TabIndex { get; init; }
public string? AccessKey { get; init; }
public Microsoft.UI.Xaml.Input.XYFocusKeyboardNavigationMode? XYFocusKeyboardNavigation { get; init; }
Expand Down Expand Up @@ -2084,6 +2086,7 @@ public ElementModifiers Merge(ElementModifiers other)
HeadingLevel = other.HeadingLevel ?? HeadingLevel,
IsDragRegion = other.IsDragRegion ?? IsDragRegion,
IsTabStop = other.IsTabStop ?? IsTabStop,
IsHitTestVisible = other.IsHitTestVisible ?? IsHitTestVisible,
TabIndex = other.TabIndex ?? TabIndex,
AccessKey = other.AccessKey ?? AccessKey,
XYFocusKeyboardNavigation = other.XYFocusKeyboardNavigation ?? XYFocusKeyboardNavigation,
Expand Down
3 changes: 3 additions & 0 deletions src/Reactor/Core/Reconciler.cs
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Expand Up @@ -3832,6 +3832,9 @@ internal void ApplyModifiers(FrameworkElement fe, ElementModifiers? oldM, Elemen
if (m.IsTabStop.HasValue && m.IsTabStop != oldM?.IsTabStop)
fe.IsTabStop = m.IsTabStop.Value;

if (m.IsHitTestVisible.HasValue && m.IsHitTestVisible != oldM?.IsHitTestVisible)
fe.IsHitTestVisible = m.IsHitTestVisible.Value;
Comment on lines +3835 to +3836

@azchohfi azchohfi Jul 6, 2026

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This only writes when HasValue, so it never resets. If an element sets .IsHitTestVisible(false) and a later render drops the modifier, the update path hands ApplyModifiers an empty ElementModifiers (Reconciler.Update.cs:239-240) and this write is skipped — the control stays click-through. The IsDragRegion/AutomationName handlers above have a clear-on-unset branch; this one (like IsTabStop) doesn't. Pooled reuse is fine since ElementPool already clears the DP, but an in-place set→unset on a retained control isn't.

Suggested change
if (m.IsHitTestVisible.HasValue && m.IsHitTestVisible != oldM?.IsHitTestVisible)
fe.IsHitTestVisible = m.IsHitTestVisible.Value;
if (m.IsHitTestVisible.HasValue && m.IsHitTestVisible != oldM?.IsHitTestVisible)
fe.IsHitTestVisible = m.IsHitTestVisible.Value;
else if (!m.IsHitTestVisible.HasValue && oldM?.IsHitTestVisible.HasValue == true)
fe.ClearValue(UIElement.IsHitTestVisibleProperty);

Would also be worth a selftest fixture covering the set→unset round-trip against a live control — the current unit test only asserts the modifier record, not the reconciler write.


if (m.TabIndex.HasValue && m.TabIndex != oldM?.TabIndex && fe is WinUI.Control tabIdxCtrl)
tabIdxCtrl.TabIndex = m.TabIndex.Value;

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10 changes: 10 additions & 0 deletions src/Reactor/Elements/ElementExtensions.cs
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Expand Up @@ -2517,6 +2517,16 @@ public static T HeadingLevel<T>(this T el, Microsoft.UI.Xaml.Automation.Peers.Au
public static T IsTabStop<T>(this T el, bool isTabStop = true) where T : Element =>
Modify(el, new ElementModifiers { IsTabStop = isTabStop });

/// <summary>
/// Sets UIElement.IsHitTestVisible — whether the element (and its subtree) can be
/// the target of pointer input. Set <c>false</c> for decorative or overlay layers
/// that should let pointer events pass through to whatever is underneath.
/// Works on any element type (Panel, Control, etc.) in WinUI 3.
/// </summary>
/// <example>Border(content).IsHitTestVisible(false)</example>
public static T IsHitTestVisible<T>(this T el, bool isHitTestVisible = true) where T : Element =>
Modify(el, new ElementModifiers { IsHitTestVisible = isHitTestVisible });

/// <summary>
/// Marks how this element participates in a window title bar's drag region
/// (<c>Microsoft.UI.Xaml.Controls.TitleBar.IsDragRegion</c>, WinApp SDK ≥ 2.1.3):
Expand Down
9 changes: 9 additions & 0 deletions tests/Reactor.Tests/ElementExtensionsCoverageTests.cs
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Expand Up @@ -202,6 +202,15 @@ public void IsEnabled_Sets_Modifier()
Assert.True(enabled.Modifiers!.IsEnabled);
}

[Fact]
public void IsHitTestVisible_Sets_Modifier()
{
var el = Button("Y").IsHitTestVisible(false);
Assert.False(el.Modifiers!.IsHitTestVisible);
var hitTestable = Button("Y").IsHitTestVisible();
Assert.True(hitTestable.Modifiers!.IsHitTestVisible);
}

[Fact]
[Obsolete("Tests the deprecated Disabled shim")]
public void Disabled_Shim_Inverts_To_IsEnabled()
Expand Down
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