Created attachment 150470 [details]
Demonstration source

I noticed that with gtk 2.18/win32 I'm only getting motion notify with left mouse button down when the mouse cursor is inside the window bounds. As soon as the mouse cursor leaves the window's bounds, no more motion notify messages come in. This worked correctly in gtk 2.16 under Win32.

I've attached a brief example code that shows the problem. Just hold down LMB over the foo bar label and move the mouse while holding down LMB. Motion notify events will come in now only as long as the mouse cursor is inside the window bounds. If you move the cursor outside of the window bounds, no more motion notify events will happen.

This might sound like an irrelevant problem but it is actually a very important issue. Just imagine that the selection rectangles in the Gimp won't react any more if the mouse cursor is outside of the window. That's pretty confusing for the user...