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Unregister hooks in ScrollViewerAssist when the ScrollViewer is unloaded #3133

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Merged
merged 2 commits into from
Mar 16, 2023
Merged

Unregister hooks in ScrollViewerAssist when the ScrollViewer is unloaded #3133

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8458eae
Unregister hooks when the ScrollViewer is unloaded
chris-crowther Mar 10, 2023
54572af
Use weak events to manage hooks
chris-crowther Mar 10, 2023
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104 changes: 53 additions & 51 deletions MaterialDesignThemes.Wpf/ScrollViewerAssist.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,9 @@ public static bool GetShowSeparators(DependencyObject element)
private static readonly DependencyProperty HorizontalScrollHookProperty = DependencyProperty.RegisterAttached(
"HorizontalScrollHook", typeof(HwndSourceHook), typeof(ScrollViewerAssist), new PropertyMetadata(null));

private static readonly DependencyProperty HorizontalScrollSourceProperty = DependencyProperty.RegisterAttached(
"HorizontalScrollSource", typeof(HwndSource), typeof(ScrollViewerAssist), new PropertyMetadata(null));

public static readonly DependencyProperty SupportHorizontalScrollProperty = DependencyProperty.RegisterAttached(
"SupportHorizontalScroll", typeof(bool), typeof(ScrollViewerAssist), new PropertyMetadata(false, OnSupportHorizontalScrollChanged));

Expand All @@ -79,50 +82,49 @@ private static void OnSupportHorizontalScrollChanged(DependencyObject d, Depende
//Based on: https://blog.walterlv.com/post/handle-horizontal-scrolling-of-touchpad-en.html
if (d is ScrollViewer scrollViewer)
{
if ((bool)e.NewValue)
if (scrollViewer.IsLoaded)
{
OnLoaded(scrollViewer, sv =>
{
if (GetSupportHorizontalScroll(sv))
{
RegisterHook(sv);
}
});
DoOnLoaded(scrollViewer);
}
else
{
OnLoaded(scrollViewer, sv =>
{
if (!GetSupportHorizontalScroll(sv))
{
RemoveHook(sv);
}
});
WeakEventManager<ScrollViewer, RoutedEventArgs>.AddHandler(scrollViewer, nameof(ScrollViewer.Loaded), OnLoaded);
WeakEventManager<ScrollViewer, RoutedEventArgs>.AddHandler(scrollViewer, nameof(ScrollViewer.Unloaded), OnUnloaded);
}
}

static void OnLoaded(ScrollViewer scrollViewer, Action<ScrollViewer> doOnLoaded)
static void OnLoaded(object? sender, RoutedEventArgs e)
{
if (scrollViewer.IsLoaded)
if (sender is ScrollViewer sv)
{
DoOnLoaded(sv);
}
}

static void DoOnLoaded(ScrollViewer sv)
{
if (GetSupportHorizontalScroll(sv))
{
doOnLoaded(scrollViewer);
RegisterHook(sv);
}
else
{
RoutedEventHandler? onLoaded = null;
onLoaded = (_, _) =>
{
scrollViewer.Loaded -= onLoaded;
doOnLoaded(scrollViewer);
};
scrollViewer.Loaded += onLoaded;
RemoveHook(sv);
}
}

static void OnUnloaded(object? sender, RoutedEventArgs e)
{
if (sender is ScrollViewer sv)
{
RemoveHook(sv);
}
}

static void RemoveHook(ScrollViewer scrollViewer)
{
if (scrollViewer.GetValue(HorizontalScrollHookProperty) is HwndSourceHook hook &&
PresentationSource.FromVisual(scrollViewer) is HwndSource source)
scrollViewer.GetValue(HorizontalScrollSourceProperty) is HwndSource source)
{
source.RemoveHook(hook);
scrollViewer.SetValue(HorizontalScrollHookProperty, null);
Expand All @@ -135,6 +137,7 @@ static void RegisterHook(ScrollViewer scrollViewer)
if (PresentationSource.FromVisual(scrollViewer) is HwndSource source)
{
HwndSourceHook hook = Hook;
scrollViewer.SetValue(HorizontalScrollSourceProperty, source);
scrollViewer.SetValue(HorizontalScrollHookProperty, hook);
source.AddHook(hook);
}
Expand Down Expand Up @@ -166,43 +169,42 @@ private static void OnBubbleVerticalScrollChanged(DependencyObject d, Dependency
{
if (d is ScrollViewer scrollViewer)
{
if ((bool)e.NewValue)
if (scrollViewer.IsLoaded)
{
OnLoaded(scrollViewer, sv =>
{
if (GetBubbleVerticalScroll(sv))
{
RegisterHook(sv);
}
});
DoOnLoaded(scrollViewer);
}
else
{
OnLoaded(scrollViewer, sv =>
{
if (!GetBubbleVerticalScroll(sv))
{
RemoveHook(sv);
}
});
WeakEventManager<ScrollViewer, RoutedEventArgs>.AddHandler(scrollViewer, nameof(ScrollViewer.Loaded), OnLoaded);
WeakEventManager<ScrollViewer, RoutedEventArgs>.AddHandler(scrollViewer, nameof(ScrollViewer.Unloaded), OnUnloaded);
}
}

static void OnLoaded(ScrollViewer scrollViewer, Action<ScrollViewer> doOnLoaded)
static void OnLoaded(object? sender, RoutedEventArgs e)
{
if (scrollViewer.IsLoaded)
if (sender is ScrollViewer sv)
{
doOnLoaded(scrollViewer);
DoOnLoaded(sv);
}
}

static void DoOnLoaded(ScrollViewer sv)
{
if (GetBubbleVerticalScroll(sv))
{
RegisterHook(sv);
}
else
{
RoutedEventHandler? onLoaded = null;
onLoaded = (_, _) =>
{
scrollViewer.Loaded -= onLoaded;
doOnLoaded(scrollViewer);
};
scrollViewer.Loaded += onLoaded;
RemoveHook(sv);
}
}

static void OnUnloaded(object? sender, RoutedEventArgs e)
{
if (sender is ScrollViewer sv)
{
RemoveHook(sv);
}
}

Expand Down