Code review comment for lp://staging/~alan-griffiths/mir/client-initiates-user-move-and-resize

I'm fairly sure we need zero more work done on resizing. All the resizing use cases are covered by existing APIs.

On the topic of client-initiated movement though, please start thinking about the Chrome/Chromium use case too: You drag a tab out of the window, that then creates a new window where the cursor remains on the same relative tab coordinate in the new window. If it's not baked in to the drag action then we'll need to be able to create that new top-level window at a precise coordinate relative to the old window (which may be the parent but can also be closed leaving just the child open).