Enumerates the various reasons for raising the ToolBarNotify event.

Values:

IG_ARTX_GUI_TOOLBAR_BUTTON_SELECTED	A button has been selected.
IG_ARTX_GUI_TOOLBAR_NONE_SELECTED	No button is selected.
IG_ARTX_GUI_TOOLBAR_HIDDEN	A button on toolbar caption is clicked.
IG_ARTX_GUI_TOOLBAR_DESTROYED	The toolbar is about to be destroyed.