is invoked during the docking procedure when the window has been moved.
on return the DockingData must contain either the old tracking rectangle
or a changed rectangle if required, additionally it must indicate if
the window should be docked or floating
Note: the tracking rectangle indicates to the user where the window would
be placed if he releases the mouse.
is invoked when the floating mode is about to be changed between
floating and docked or vice versa
if returned FALSE the floating mode will not be changed
is invoked during the docking procedure when the window has been moved.
on return the DockingData must contain either the old tracking rectangle
or a changed rectangle if required, additionally it must indicate if
the window should be docked or floating
Note: the tracking rectangle indicates to the user where the window would
be placed if he releases the mouse.
is invoked when the floating mode is about to be changed between
floating and docked or vice versa
if returned FALSE the floating mode will not be changed