MouseAction

maNone	No user interaction is possible. The only way to apply a mouse controlled action is by utilizing the mouse events.
maPan	The scale can be panned by pressing and holding the left mouse button. The scale will then follow the mouse movement.
maZoomDrag	This mode enables the user to increase or to decrease the range of the scale. The left mouse button has to be pressed and held down. The range of the scale will then follow the mouse movement keeping the center in place.
maZoom	This mode allows to shift a particular end of a scale (which results in zooming the scale range) by clicking and dragging the scale. Clicking the left (top) half of the scale will shift the left (top) boundary of the scale, clicking the right (bottom) half of the scale will shift the right (bottom) boundary of the scale.

Hint:

Double clicking the scale toggles the MouseAction mode between maPan and maZoom if any of these two modes is active, for all other modes a double click does not have any effect.