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PresentationFramework: Safer tooltip handling #11463

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PresentationFramework: Safer tooltip handling #11463

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19 changes: 16 additions & 3 deletions ...osoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/PopupControlService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -330,7 +330,7 @@ private void BeginShowToolTip(DependencyObject o, ToolTipService.TriggerAction t
switch (triggerAction)
{
case ToolTipService.TriggerAction.Mouse:
if (SafeArea != null)
if (HasValidSafeArea)
{
// the mouse has moved over a tooltip owner o, while still
// within the safe area of the current tooltip (which must be from mouse).
Expand Down Expand Up @@ -909,8 +909,8 @@ private void SetSafeArea(ToolTip tooltip)

private bool MouseHasLeftSafeArea()
{
// if there is no SafeArea, the mouse didn't leave it
if (SafeArea == null)
// if there is no valid SafeArea, the mouse didn't leave it
if (!HasValidSafeArea)
return false;

// if the current tooltip's owner is no longer being displayed, the safe area is no longer valid
Expand All @@ -926,6 +926,17 @@ private bool MouseHasLeftSafeArea()

private ConvexHull SafeArea { get; set; }

private bool HasValidSafeArea
{
get
{
// There are plenty of Watsons which indicate that source might get disposed
// (i.e. underlying HWND gets destroyed) while we are still holding on it.
// If such a case treat it as if there is no valid safe area.
return SafeArea != null && SafeArea.IsValid;
}
}

#endregion

#endregion
Expand Down Expand Up @@ -1374,6 +1385,8 @@ internal ConvexHull(PresentationSource source, List<NativeMethods.RECT> rects)
}
}

internal bool IsValid => !_source.IsDisposed;
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Copilot AI Feb 18, 2026

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The IsValid property should handle the case where _source might be null to prevent potential NullReferenceException. While _source is expected to be non-null based on the constructor being called only when presentationSource is not null (line 844-905), defensive programming suggests checking for null. Consider changing to: internal bool IsValid => _source != null && !_source.IsDisposed;

Suggested change
internal bool IsValid => !_source.IsDisposed;
internal bool IsValid => _source != null && !_source.IsDisposed;

Copilot uses AI. Check for mistakes.

// sort by y (and by x among equal y's)
private void SortPoints(PointList points)
{
Expand Down