frontbuffer(3G)

NAME
     backbuffer, frontbuffer - enable and disable drawing to the back or front
     buffer

C SPECIFICATION
     void backbuffer(Boolean b)

     void frontbuffer(Boolean b)

PARAMETERS
     b    is either TRUE or FALSE.

          TRUE enables updating in the back/front bitplane buffer.

          FALSE disables updating in the back/front bitplane buffer.

DESCRIPTION
     The GL supports four separate framebuffers:  pop-up, overlay, underlay,
     and normal.  Three of these framebuffers, overlay, underlay, and normal,
     can be configured in double buffer mode.  When so configured, a
     framebuffer includes two color bitplane buffers:  one visible bitplane
     buffer, called the front buffer, and one non-visible bitplane buffer,
     called the back buffer.  The commands swapbuffers and mswapbuffers
     interchange the front and back buffer assignments.

     By default, when a framebuffer is configured in double buffer mode,
     drawing is enabled in the back buffer, and disabled in the front buffer.
     frontbuffer and backbuffer enable and disable drawing into the front and
     back buffers, allowing the default to be overriden.  It is acceptable to
     enable neither front nor back, either front or back, or both front and
     back simultaneously.  Note, for example, that z-buffer drawing continues
     to update the z-buffer with depth values when neither the front buffer
     nor the back buffer is enabled for drawing.

     frontbuffer and backbuffer state is maintained separately for each of the
     overlay, underlay, and normal framebuffers.  Calls to these routines
     affect the framebuffer that is currently active, based on the current
     drawmode.

     backbuffer is ignored when the currently active framebuffer is in single
     buffer mode.  frontbuffer is also ignored when the currently active
     framebuffer is in single buffer mode, unless zdraw is enabled for that
     framebuffer (see zdraw).

     After each call to gconfig, backbuffer is enabled and frontbuffer is
     disabled.

SEE ALSO
     drawmode, doublebuffer, getbuffer, gconfig, singlebuffer, swapbuffers,
     zdraw, rightbuffer, leftbuffer
NOTE
     IRIS-4D G, GT, and GTX models, the Personal Iris, Indigo Entry, Indy, XL,
     XS, XS24, XZ, Elan and Extreme systems do not support double buffer
     operation in the overlay and underlay framebuffers.  IRIS-4D
     RealityEngine model does not support double buffer operation in the
     underlay framebuffer.

     At most four color buffers, such as front-left, front-right, back-left,
     back-right, and zdraw, can be rendered into simultaneously on the IRIS-4D
     RealityEngine model.