A %gr graphics region may have an icon resource 'attached' to it. The icon can
be moved freely around the graphics window with the mouse. Control of the icon
is maintained by the call-back function attached to the %gr window with the
caret modifier (^).
The NAME argument is that used for the resource that is included in your
program. The X and Y values, initially hold the location the image is draw to.
They also hold the new position when the image is moved. The clearwin_info@
parameter 'DRAGGED_ICON' is set to the value of the handle of the moved icon.
The handle is initially obtained as the returned from the function. The
call-back function may modify the X and Y values if required. The purpose of
this may be to 'lock' the image onto the horizontal or vertical plane by
continuously setting either the X or Y variables to a constant value.
When the icon is dropped clearwin_info@ parameter 'DROPPED_ICON' is set to the
handle of the icon. A graphics icon can be removed with a call to
The width and height parameters should be set at zero except when the icon image
occupies less than the possible 32x32 icon area e.g. 16x16. A small icon can be
constructed by starting at the top-left corner and filling the remaining unused
area with the 'transparent' colour. If you do not specify the correct size of
the icon then the unused area will be detected by the mouse.