imakebackground(3G)

NAME
     imakebackground - registers the screen background process

C SPECIFICATION
     void imakebackground()

PARAMETERS
     none

DESCRIPTION
     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
          *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
     winopen

NOTE
     This routine is available only in immediate mode.