How to increase scrollbar width in WPF ScrollViewer?

I am working on a touch screen on a small device and the custom width of the scroll-bar is no good as one of my requirements is that everything needs to be doable by finger gestures.

How can I set the width of the WPF ScrollViewer scrollbar?

Note that I don't wanna change the width of all the scrollbars on the device (doable through windows settings) - only the ones in my app.

Solution

The ScrollBar template reaches out for system parameters to determine its width/height (depending on orientation). Therefore, you can override those parameters:

<ScrollViewer>
    <ScrollViewer.Resources>
        <sys:Double x:Key="{x:Static SystemParameters.VerticalScrollBarWidthKey}">100</sys:Double>
    </ScrollViewer.Resources>
</ScrollViewer>