imakebackground(3G)					   imakebackground(3G)

NAME    [Toc]    [Back]

     imakebackground - registers the screen background process

C SPECIFICATION    [Toc]    [Back]

     void imakebackground()

PARAMETERS    [Toc]    [Back]

     none

DESCRIPTION    [Toc]    [Back]

     imakebackground registers a process that maintains	the screen background.
     Call it before winopen.  The process should redraw	the screen background
     each time it receives a REDRAW event.

     There is only one background so only one imakebackground process can run
     at	a time.	Any existing imakebackground process is	killed when a new one
     is	started.

     Because the X Window System's inability to	change the mode	(called	the
     visual in xspeak) of a window conflicts with the GL's freedom to change
     modes at any time,	imakebackground	processes cannot paint on the real
     background	(called	the root window	in xspeak).  Instead a new window is
     created with the correct visual. This window is kept at the bottom	of the
     stack of windows just above the screen background.	This imakebackground
     window works better when it is what in xspeak is called an	override-
     redirect window. In simple	terms this means the window is not managed by
     the window	manager.

     A window that is managed is likely	to be given borders by the window
     manager.  Currently only 4Dwm(1X) and mwm(1X) understand the request to
     turn off the borders. Also	the window manager will	post the usual window
     menu for a	managed	window.	You cannot access the root menu.  A managed
     window is useful, however,	when the imakebackground process is running in
     color map mode (see cmode(3G)). The window	manager	is the only process
     that can install the GL color map according to its	own color map
     management	policies so that the window is displayed correctly at the
     expected times.

     Because of	this dichotomy,	there is an X resource that controls whether
     or	not the	imakebackground	window is managed.  The	full resource class is

	  Name.GL.GLBackground.Manage

     Name is the name of the window taken from the argument to winopen The
     resource can have the values true or false. The default is	false. In
     other words if the	resource isn't specified the imakebackground window is
     not managed. We recommend using managed windows for cmode(3g) processes
     and non-managed windows for RGBmode(3g) processes.	For example the
     following entries in the X	resource database






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imakebackground(3G)					   imakebackground(3G)



	  *GLBackground.Manage:	false
	  texback*GLBackground.Manage: true

     cause background windows to be unmanaged except for a background program
     called texback which is known to be a cmode(3g) program.

SEE ALSO    [Toc]    [Back]

     winopen

NOTE    [Toc]    [Back]

     This routine is available only in immediate mode.


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