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ScrollViewerAssist: Avoid TargetInvocationException on WinForms application shutdown #4015

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Merged
Keboo merged 1 commit into from
Mar 6, 2026
+42 −1
Merged

ScrollViewerAssist: Avoid TargetInvocationException on WinForms application shutdown #4015

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43 changes: 42 additions & 1 deletion src/MaterialDesignThemes.Wpf/ScrollViewerAssist.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,12 @@ static void OnUnloaded(object? sender, RoutedEventArgs e)
}
}

static void RemoveHandlers(ScrollViewer scrollViewer)
{
WeakEventManager<ScrollViewer, RoutedEventArgs>.RemoveHandler(scrollViewer, nameof(ScrollViewer.Loaded), OnLoaded);
WeakEventManager<ScrollViewer, RoutedEventArgs>.RemoveHandler(scrollViewer, nameof(ScrollViewer.Unloaded), OnUnloaded);
}

static void RemoveHook(ScrollViewer scrollViewer)
{
if (scrollViewer.GetValue(HorizontalScrollHookProperty) is HwndSourceHook hook &&
Expand All @@ -138,12 +144,20 @@ static void RegisterHook(ScrollViewer scrollViewer)
IntPtr Hook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
const int WM_MOUSEHWHEEL = 0x020E;
const int WM_DESTROY = 0x0002;
const int WM_NCDESTROY = 0x0082;
switch (msg)
{
case WM_MOUSEHWHEEL when scrollViewer.IsMouseOver:
int tilt = (short)((wParam.ToInt64() >> 16) & 0xFFFF);
scrollViewer.ScrollToHorizontalOffset(scrollViewer.HorizontalOffset + tilt);
return (IntPtr)1;
case WM_DESTROY:
case WM_NCDESTROY:
RemoveHandlers(scrollViewer);
var source = PresentationSource.FromVisual(scrollViewer) as HwndSource;
source?.RemoveHook(Hook);
break;
}
return IntPtr.Zero;
}
Expand Down Expand Up @@ -196,6 +210,12 @@ static void OnUnloaded(object? sender, RoutedEventArgs e)
}
}

static void RemoveHandlers(ScrollViewer scrollViewer)
{
WeakEventManager<ScrollViewer, RoutedEventArgs>.RemoveHandler(scrollViewer, nameof(ScrollViewer.Loaded), OnLoaded);
WeakEventManager<ScrollViewer, RoutedEventArgs>.RemoveHandler(scrollViewer, nameof(ScrollViewer.Unloaded), OnUnloaded);
}

static void RemoveHook(ScrollViewer scrollViewer)
{
scrollViewer.RemoveHandler(UIElement.MouseWheelEvent, (RoutedEventHandler)ScrollViewerOnMouseWheel);
Expand All @@ -204,7 +224,28 @@ static void RemoveHook(ScrollViewer scrollViewer)
static void RegisterHook(ScrollViewer scrollViewer)
{
RemoveHook(scrollViewer);
scrollViewer.AddHandler(UIElement.MouseWheelEvent, (RoutedEventHandler)ScrollViewerOnMouseWheel, true);
if (PresentationSource.FromVisual(scrollViewer) is HwndSource source)
{
HwndSourceHook hook = Hook;
source.AddHook(hook);
scrollViewer.AddHandler(UIElement.MouseWheelEvent, (RoutedEventHandler)ScrollViewerOnMouseWheel, true);
}

IntPtr Hook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
const int WM_DESTROY = 0x0002;
const int WM_NCDESTROY = 0x0082;
switch (msg)
{
case WM_DESTROY:
case WM_NCDESTROY:
RemoveHandlers(scrollViewer);
var source = PresentationSource.FromVisual(scrollViewer) as HwndSource;
source?.RemoveHook(Hook);
break;
}
return IntPtr.Zero;
}
}

// This relay is only needed because the UIElement.AddHandler() has strict requirements for the signature of the passed Delegate
Expand Down
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