Adding a swipe gesture to open SplitView Pane

Interesting question! 🙂

I recently created a SwipeableSplitView which extends the SplitView control to enable a swipe from left edge gesture when the DisplayMode is set to Overlay (as I don’t see the point to have it in other modes, but feel free to extend it whenever needed).

All I am doing is, inside the control’s style, create another layer on top of the PaneRoot layer and handle all the gestures there.

<Grid x:Name="PaneRoot" ManipulationMode="TranslateX" Grid.ColumnSpan="2" HorizontalAlignment="Left" Background="{TemplateBinding PaneBackground}" Width="{Binding TemplateSettings.OpenPaneLength, RelativeSource={RelativeSource Mode=TemplatedParent}}">
    <Grid.Clip>
        <RectangleGeometry x:Name="PaneClipRectangle">
            <RectangleGeometry.Transform>
                <CompositeTransform x:Name="PaneClipRectangleTransform" />
            </RectangleGeometry.Transform>
        </RectangleGeometry>
    </Grid.Clip>
    <Grid.RenderTransform>
        <CompositeTransform x:Name="PaneTransform" TranslateX="{Binding RenderTransform.TranslateX, ElementName=PanArea}" />
    </Grid.RenderTransform>
    <Border Child="{TemplateBinding Pane}" />
    <Rectangle x:Name="HCPaneBorder" Fill="{ThemeResource SystemControlForegroundTransparentBrush}" HorizontalAlignment="Right" Visibility="Collapsed" Width="1" x:DeferLoadStrategy="Lazy" />
</Grid>

<!--a new layer here to handle all the gestures -->
<Grid x:Name="OverlayRoot" Grid.ColumnSpan="2">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="{Binding TemplateSettings.OpenPaneGridLength, RelativeSource={RelativeSource Mode=TemplatedParent}}" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <!--the actual element for panning, manipulations happen here-->
    <Rectangle x:Name="PanArea" Fill="Transparent" ManipulationMode="TranslateX" Width="{Binding PanAreaThreshold, RelativeSource={RelativeSource Mode=TemplatedParent}}" Grid.Column="1">
        <Rectangle.RenderTransform>
            <CompositeTransform TranslateX="{Binding PanAreaInitialTranslateX, RelativeSource={RelativeSource Mode=TemplatedParent}}" />
        </Rectangle.RenderTransform>
    </Rectangle>
    <!--this is used to dismiss this swipeable pane-->
    <Rectangle x:Name="DismissLayer" Fill="Transparent" Grid.Column="2" />
</Grid>

While updating the TranslateX of the new layer’s transform object, I am also updating the PaneRoot‘s to keep their position in sync.

void OnManipulationStarted(object sender, ManipulationStartedRoutedEventArgs e)
{
    _panAreaTransform = PanArea.RenderTransform as CompositeTransform;
    _paneRootTransform = PaneRoot.RenderTransform as CompositeTransform;

    if (_panAreaTransform == null || _paneRootTransform == null)
    {
        throw new ArgumentException("Make sure you have copied the default style to Generic.xaml!!");
    }
}

void OnManipulationDelta(object sender, ManipulationDeltaRoutedEventArgs e)
{
    var x = _panAreaTransform.TranslateX + e.Delta.Translation.X;

    // keep the pan within the bountry
    if (x < PanAreaInitialTranslateX || x > 0) return;

    // while we are panning the PanArea on X axis, let's sync the PaneRoot's position X too
    _paneRootTransform.TranslateX = _panAreaTransform.TranslateX = x;
}

void OnManipulationCompleted(object sender, ManipulationCompletedRoutedEventArgs e)
{
    var x = e.Velocities.Linear.X;

    // ignore a little bit velocity (+/-0.1)
    if (x <= -0.1)
    {
        CloseSwipeablePane();
    }
    else if (x > -0.1 && x < 0.1)
    {
        if (Math.Abs(_panAreaTransform.TranslateX) > Math.Abs(PanAreaInitialTranslateX) / 2)
        {
            CloseSwipeablePane();
        }
        else
        {
            OpenSwipeablePane();
        }
    }
    else
    {
        OpenSwipeablePane();
    }
}

Keep in mind that because the IsPaneOpen property is not virtual, I have to create another one IsSwipeablePaneOpen to wrap the former around. So whenever you feel like using the IsPaneOpen property, use IsSwipeablePaneOpen instead.

This is how it works in a demo app I created in GitHub. You can find the full source code here.

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Credits

• The SplitView template was generated from Koen Zwikstra’s awesome Visual Studio UWP templates.
• Page animations and some other implementations were inspired by this post
  from Jerry Nixon.