WPF overlay across multiple windows

I have a WPF application using multiple independent windows. I would like to draw a line from one of the windows to another one. This needs to be controlled programmatically and if one of the wind开发者_开发问答ows is moved, this line needs to be updated accordingly.

What's the best way to do something like this? A transparent window on top of all others?

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Ok, so all in all my solution is pretty simple and works well. I create a regular Window with Background=Transparent, ShowInTaskbar=False and the Size matching the screen (or multiple screens if attached). Additionally, I set TopMostto true. In this OverlayWindow I have a canvas where I can place objects or draw to. To allow other modules and windows of my application to draw overlays, I have a global OverlayManagerwhich allows to add and remove overlays, such as lines.