WPF zoom canvas and maintain scroll position
- by Alex McBride
I have a Canvas element, contained within a ScrollViewer, which I'm zooming using ScaleTransform. However, I want to be able to keep the scroll position of the viewer focused on the same part of the canvas after the zoom operation has finished. Currently when I zoom the canvas the scroll position of the viewer stays where it was and the place the user was viewing is lost.
I'm still learning WPF, and I've been going backwards and forwards a bit on this, but I can't figure out a nice XAML based way to accomplish what I want. Any help in this matter would be greatly appreciated and would aid me in my learning process.
Here is the kind of code I'm using...
<Grid>
<ScrollViewer Name="TrackScrollViewer" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<Canvas Width="2560" Height="2560" Name="TrackCanvas">
<Canvas.LayoutTransform>
<ScaleTransform ScaleX="{Binding ElementName=ZoomSlider, Path=Value}"
ScaleY="{Binding ElementName=ZoomSlider, Path=Value}"/>
</Canvas.LayoutTransform>
<!-- Some complex geometry describing a motor racing circuit -->
</Canvas>
</ScrollViewer>
<StackPanel Orientation="Horizontal" Margin="8" VerticalAlignment="Top" HorizontalAlignment="Left">
<Slider Name="ZoomSlider" Width="80" Minimum="0.1" Maximum="10" Value="1"/>
<TextBlock Margin="4,0,0,0" VerticalAlignment="Center" Text="{Binding ElementName=ZoomSlider, Path=Value, StringFormat=F1}"/>
</StackPanel>
</Grid>
