Hot Keys for Use With Tools
The CTRL, Shift and ALT keys give special control when using tools. Additionally Esc will cancel any tool that has not been applied yet.
At any time while defining a tool area the Esc key can be used to cancel the action. This is useful for example if you start a Crop action and decide you don't want to crop.
At any time during a tool usage you can press and hold the CTRL key and move your cursor to adjust the starting position of a tool. For example you draw a rectangle area for the mask tool and then press and hold the CTRL and move the position of the rectangle.
At any time during a tool usage you can press and hold the Shift key and the area being defined will be constrained to a square or circle depending on the tool.
At any time during a tool usage you can press and hold the ALT key and the area being defined will be determined using the starting position of the tool usage as the center rather than the upper left corner.