WPF: Canvas mouse events not firing on empty space

A control with no background color set (explicitly or through styles etc) will default to having a background color of null - making it not hit-testable.

If you set the background to "Transparent" (or anything other than null ({x:Null})) then it will be able to pick up the mouse events

Set the background color. It defaults to null.

Use Background="White" for instance.