gpr_allocate_buffer() — Apollo Domain/OS SR10.4.1

GPR_$ALLOCATE_BUFFER              GPR Calls               GPR_$ALLOCATE_BUFFER


NAME
     gpr_$allocate_buffer - allocates a buffer bitmap in display memory.

FORMAT
     gpr_$allocate_buffer (primary_bitmap, buffer_bitmap, status)

DESCRIPTION
     This routine allocates a buffer bitmap in display memory having the same
     size and attributes as a specified display bitmap.  Use this call to
     establish a buffer bitmap for a double buffer application.  The buffer
     bitmap will have the same rectangle properties as the primary bitmap.
     The buffer bitmap will also inherit the attribute block of the primary
     bitmap.  (However, after creating the buffer bitmap, you may wish to
     allocate a separate attribute block for it.)

   Input Parameters
     primary_bitmap
          The descriptor of a bitmap in gpr_$bitmap_desc_t format.  (The
          gpr_$init call will return this descriptor.)  This is a 4-byte
          integer.  You must specify a display bitmap; you cannot specify a
          hidden display memory bitmap, main memory bitmap, or external file
          bitmap.

   Output Parameters
     buffer_bitmap
          Descriptor of the allocated bitmap, in gpr_$bitmap_desc_t format.
          This is a 4-byte integer.

     status
          Completion status, in status_$t format.

SEE ALSO
     gpr_$select_display_buffer.

NOTES
     The buffer bitmap is  invisible  until  you  make  it  visible  with  the
     gpr_$select_display_buffer call.

     Currently, the only node that permits  double  buffering  is  the  DN590;
     furthermore,  the  DN590  permits  only one buffer bitmap.  If you try to
     allocate more than one buffer bitmap, GPR will return the following error
     code:
     gpr_$no_more_fast_buffers
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