In WPF, how can I capture mouse on a Canvas and still find what controls the cursor is hovering over?

2
votes

I have a custom Canvas control (inherited from Canvas) overlaid over a large area of User Controls. The idea is to draw paths between user controls (i.e. connector lines).

To capture mouse movement, I call Mouse.Capture(theCanvas) on MouseDown. This works beautifully, but the user controls under the canvas obviously no longer receive mouse events. Mouse.DirectlyOver always shows the canvas, so I can't really fake it by peeking at the current position and seeing which user control it's over.

So, I still need the Canvas for drawing paths, but how can I solve this one of the following ways:

  1. Peek under the Canvas and see what the topmost control is right under it?
  2. Get this MouseDown -> Track MouseMoves -> MouseUp workflow to work on the canvas without mouse captures?

Any other ideas welcome...

1
c#wpfmouse
What kinds of mouse events do the controls under the canvas need to receive? - Rob Fonseca-Ensor
@Rob, mouse up/down/move (i.e. move is used to determine whether or not it's a valid target and change the line color to green, up is used to determine whether user actually wants to make the connection at that control, etc) - Brandon

1 Answers

0
votes

I'd agree that those are your two options. If you want to only forward some clicks to your usercontrols, then go with option 1, and hit test the controls under the canvas.

If you need your usercontrols to behave as though there is nothing covering them (textboxes, buttons etc), then i'd recommend using the PreviewMouseMove event on the user control's parent, as this can pick up and optionally "handle" events before the controls get at the event, but it won't block the event if you don't set handled to true