SuperBitMap windows are created by setting the WFLG_SUPER_BITMAP flag, or
by specifying the wa_superbitmap tag in the openwindowtaglist() call.  a
pointer to an allocated and initialized bitmap structure must be provided.

A SuperBitMap window requires the application to allocate and initialize
its own bitmap.  This entails allocating a bitmap structure, initializing
the structure and allocating memory for the bit planes.

Allocate a bitmap structure with the exec allocmem() function.  then use
the graphics function initbitmap() to initialize the bitmap structure:

    void InitBitMap( struct BitMap *bitMap, long depth,
                     long width, long height );

initbitmap() fills in fields in the bitmap structure describing how a
linear memory area is organized as a series of one or more rectangular
bit-planes.

Once you have allocated and initialized the bitmap structure, use the
graphics library function allocraster() to allocate the memory space for
all the bit planes.

    PLANEPTR AllocRaster( unsigned long width, unsigned long height );

The example listed in the next section shows how to allocate a bitmap
structure, initialize it with initbitmap() and use allocraster() function
to set up memory for the bitplanes.

 graphics and layers functions for superbitmap windows 
 superbitmap window example