Many times we are dragging an icon, a view selector or other element that supports drag and drop, but the image window on which we want to act is not the active window, and the area on which we drop the item is obstructed by other windows. For example, this happens often to apply masks. If you press and release SHIFT while dragging are over an image, the window in question is automatically activated, allowing us to continue with the action we were doing.
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