Question

I have a WPF scrollViewer that I use for panning (MouseDown, MouseMove, MouseUp) and I would like to include an acceleration effect that incorporates inertia. So, if the mouse moves beyond a threshold speed and I release the mouse, it continues to pan but slows down as a function of the initial speed. Any ideas, thoughts or examples?

Answer 1

I’ve done basically this before and started by looking at ScrollViewer but in the end threw it away and used a Viewbox with a Canvas as the child for absolute positioning of content (I was supporting zoom aswel as scroll, it was basically DeepZoom without the scaled images for zooming so there was pixelation when zoomed right in). I wrote code for determining the gesture direction and the speed of the gesture from the mouse events and converted this to a scroll direction and speed and then animated the Canvas.Left and Canvas.Top properties of the scrollable content (which was in the Children collection of the Viewbox’s child Canvas) with DoubleAnimation. It worked well, however there may be a better way…heres a thread suggesting hosting DeepZoom in WPF via a Frame control (although I wouldn’t do it that way).

EDIT: Basically the ScrollViewer was just too restricting. Even if you get into the ControlTemplate and get references to the ScrollBars directly, it is the position of the Thumb of these scrollbars that you would need to animate and I’m pretty sure this is what I found I couldn’t do (it was almost 3 years ago 🙂