There are 6 mouse modes in the idp3 roi window.  "None" is the default.
These modes include:

 None.  Movement of the cursor in the roi window causes the x and
	y coordinates of the pixel plus its value to be printed
	at the bottom of the display.  Clicking any mouse button
	has no effect.

 Cross Section.  Define an image cross section by pressing 
	one of the mouse buttons at the beginning of the cross
	section, dragging to the end of the cross section, and
	releasing the mouse button.

 Radial Profile.  Define a radial profile by pressing one
	of the mouse buttons at the center of the radial profile,
	dragging to the outside edge of the radial profile circle,
	and releasing the mouse button.

 Polygon.  Define a polygon by pressing one of the mouse
	buttons at the points in the image that define the polygon
	shape.  There must be at least 3 points in the polygon.  The
	polygon is automatically closed when a point is double clicked.
	Do not close the polygon by clicking again at the polygon
	origin.

 Move Polygon.  The polygon shape may be maintained but moved
	to a different area of the roi with the move polygon option.
	Press one of the mouse buttons somewhere in the interior of
	the polygon, drag the polygon to the desired location, and
	release the mouse button.  Since the polygon cannot go outside
	the roi, it is truncated when it collides with an edge.  New
	polygon image statistics are computed when the mouse button
	is released.  The polygon movement may be undone by the Undo
	option in the Plot/Polyon menu.

 Edit Polygon.  The polygon shape may be edited by dynamically
	adjusting any of its points.  Press one of the mouse buttons
	at the point that is to be modified, drag to the desired
	location, and release the mouse button.  New polygon image
	statistics are computed when the mouse button is released.
	The editing may be undone by the Undo option in the Plot/Polygon 
	menu.