Option Menus
  ------------

  Option Menus are a topic which deserves special consideration, because
  they are abit different from what you might expect.  As the Pulldown
  example resource file demonstrates, one may create a cascade button
  before or after the menu which is controlled by the cascade.  One might
  reasonably assume that the same is true for option menus.

  Unfortunately, this is an incorrect assumption.  One MUST first create
  the pulldown menu which displays the available options, and THEN invoke
  the convenience function XmCreateOptionMenu.  This may or may not be a
  bug, depending on your point of view.

  The widget called an OptionMenu is really a row column with two managed
  children: a label, and a cascade.  The significant issue is the size of
  the cascade: it is forced to be wide enough for the longest selection
  on the pulldown menu.  One cannot after the fact set the subMenuId on
  the cascade, because the cascade does not generally size itself based
  on the subMenu elements: normally cascade buttons size themselves based
  on their label.

  One might assume that the RowColumn created by XmCreateOptionMenu would
  have a special set_values() method which does the appropriate thing
  when subMenuId is set, but this is clearly not the case: the set_values() 
  method does something, but it certainly is not appropriate.  Expect a 
  core dump if you try it.

  So, if you want to use option menus, do it as shown in this example:
  first create the pulldown menu using XmCreatePulldownMenu, then create
  the `OptionMenu' using XmCreateOptionMenu.  The order of creation is
  determined by the order of the widget names in the parent's wcChildren
  resource:

    *com.wcChildren:        doMenu, undoMenu, doOption, undoOption

  Here is a trouble shooting tip: if you use XmCreateOptionMenu and the
  cascade button's label is `<optMenName>_cascadeBtn' then you do not
  have the subMenuId set properly on the option menu.  Check for spelling
  on the resource name, on the resource value, and possibly use
  `*wcTrace: True' to make sure you give the right name for the pulldown
  menu.

  Also, remember to make the menu's initially unmanaged by setting
  wcManaged: False on each menu.  You can't do this globally,
  unfortunately, because there is no actual Motif widget class named
  XmPulldownMenu.  Sigh.

----------------------------------------------------------------------

#*wcTrace:		True

Mri.wcChildren:		com
Mri.title:		Mri using M4.OptMenu

*com.wcClassName: XmRowColumn
*com.wcChildren:  quit, doMenu, undoMenu, nextMenu, doOption, undoOption, next

*quit.wcClassName:		XmPushButton
*quit.labelString:		Push this button to quit the Option Menu demo
*quit.activateCallback:		WcExitCB

*doOption.wcConstructor:	XmCreateOptionMenu
*doOption.labelString:		Do It
*doOption.subMenuId:		*doMenu

*undoOption.wcConstructor:	XmCreateOptionMenu
*undoOption.labelString:	Undo It
*undoOption.subMenuId:		*undoMenu

*next.wcConstructor:		XmCreateOptionMenu
*next.subMenuId:		*nextMenu

*doMenu.wcConstructor:		XmCreatePulldownMenu
*doMenu.wcManaged:		False
*doMenu.wcChildren:		opt1, opt2

*undoMenu.wcConstructor:	XmCreatePulldownMenu
*undoMenu.wcManaged:		False
*undoMenu.wcChildren:		opt1, opt2, opt3

*nextMenu.wcConstructor:	XmCreatePulldownMenu
*nextMenu.wcManaged:		False
*nextMenu.wcChildren:		opt2, opt1, opt2, opt3, opt1

! Note that the specification for buttons opt1 and opt2 are actually used
! twice each: both menus have children named opt1 and opt2, so the
! children of both menus will have these same resources, and thus, will
! use the following resource specifications:

*opt1.wcClassName:	XmPushButton
*opt1.labelString:	Now

*opt2.wcClassName:	XmPushButton
*opt2.labelString:	Wat's the rush!!

*opt3.wcClassName:	XmPushButton
*opt3.labelString:	My Mistake...