Usage
Click the xy toggle button to activate it. The label of the toggle will change to x. Clicking it again will change the label to y. Clicking it again will change the label to x=y and one more click will change it back to xy.
Comments
This toggle button is for interactive manipulation only. If the keyboard toggle button is active as well, the xy toggle has no influence. x and y refer to the horizontal (x) and vertical (y) movements of the mouse with respect to the active window.
When set to x=y, the y transformation will be equal and simultaneous.
