Event capturing on Mac is quite different from that seen on Windows.

While on Windows mouse move events are only captured when the cursor is over a window. On Mac any mouse movement is captured.

Another difference is that the window where events will be added on Windows is the window under the cursor and on Mac it is the active window.

It's as if, on the Mac, the mouse grab was always enabled for the active window.

But eyedropper doesn't work between different windows because when clicking on a different window, it becomes the activated window and the modal operator events of the other window are not fired.

The workaround for this patch is to partially simulate the mouse capture seen in Windows.

When the grab mouse is activated, the window reference is saved in the system, and this window is used in the processing of mouse events.

Also the window is prevented from being activated if there is a window "capturing" the mouse events.