If the same operation is done, but Ctrl or Shift is pressed during the drag button-up or the second mouse click, operation is different. In this case, the area is marked by a dotted highlighting box, and a subsequent button 3 press will complete the operation. A press in the same window will cause the area defined by the first and second points to be shrunk by the ratio of the diagonals of the rectangles defined by point 1, point 2 and point 1, point 3. To zoom in a lot, point 2 is much closer to point 1 than point 3 is to point 1. Alternatively, a button 3 press in a different window will display the boxed area of the first window in the second window.
If Shift or Ctrl is held down before the initial button 3 press in a drawing window, a pan operation will be initiated instead of the zoom, the same as if button 2 was pressed.
In the layer menu, button 3 enables layer blinking, if neither of Shift or Ctrl is pressed. Pressing and holding button 3 over a layer entry in the layer table will cause that layer to blink periodically in the drawing windows, while button 3 remains pressed. Layers that happen to have the same color as the selected blinking layer will also blink, since the operation is sensitive only to the layer color.
In combination with Shift and Ctrl, clicking with button 3 on a layer entry provides a shortcut: