I have a Dockpanel with items inside a Canvas. The Dockpanel and any other items (Grid etc) that I place inside the Canvas, only take up their minimum required space. How do
The Canvas panel doesn't really support that.
It's very basic - it just allows you to position children absolutely by using Top, Bottom, Left and Right, and it always gives them just the space they need.
So usually you would use a Grid with just 1 column and 1 row instead.
You can however bind the width and height of the DockPanel to the width and height of the Canvas. That way the DockPanel will always fill the Canvas.