Clipping WPF elements in a canvas

Question

I am working on an interactive WPF graph/tree tool and have nodes and links between them placed in a canvas. The nodes are usercontrols and the links are simply Line shapes, and currently the links go from the centre of a node to another node's centre.

The problem arise when I want the nodes to be slightly transparent and one sees the links behind the nodes. I figured the most convenient solution would be to apply clipping or opacitymask to the lines, so they are not drawn behind the nodes, but I can't for the life of me figure out how?

Basically I can't figure out a bounding box geometry from the nodes to use as a clipping geometry for the lines. I am also interested in alternative solutions, of course!

Answer 1

It would seem to me like you're overthinking the solution. Why not just change the logic for the links so that the lines begin/end at the correct side of the node instead of starting from the center??? You should only need to do a little more math to accomplish this.

That said, to get the bounding box of a Visual you can use the VisualTreeHelper::GetContentBounnds helper method.

Answer 2

The VisualTreeHelper.GetContentBounds() method seems to return Empty everytime.

An alternative solution to this problem is answered at

http://stackoverflow.com/questions/1737509/connecting-two-wpf-canvas-elements-by-a-line-without-using-anchors/1737536#1737536

that uses bounding boxes to find intersection points to draw the lines from/to.