NAME                                                              (V36)
    CreateBehindHookLayer -- Create a new layer behind all existing layers,
                             using supplied callback BackFill hook.

SYNOPSIS
    result = CreateBehindHookLayer(li,bm,x0,y0,x1,y1,flags,hook,[,bm2])
    d0                             a0 a1 d0 d1 d2 d3 d4    a3   [ a2 ]

    struct layer *createbehindhooklayer(struct layer_info *,
                  struct bitmap *, long, long, long,
                  LONG, LONG, struct hook *, ... );

FUNCTION
    Create a new layer of position and size (x0,y0)->(x1,y1)
    Make this layer of type found in flags.
    Install Layer->BackFill callback hook.
    If SuperBitMap, use bm2 as pointer to real SuperBitMap,
    and copy contents of Superbitmap into display layer.
    If this layer is a backdrop layer then place it behind all
    other layers including other backdrop layers. If this is
    not a backdrop layer then place it behind all nonbackdrop
    layers.

    Note: when using SUPERBITMAP, you should also set LAYERSMART flag.

INPUTS
    li - pointer to LayerInfo structure
    bm - pointer to common bitmap used by all layers
    x0,y0 - upper left hand corner of layer
    x1,y1 - lower right hand corner of layer
    flags - various types of layers supported as bit sets.
            (for bit definitions, see graphics/layers.h )
    hook -  Layer->BackFill callback hook which will be called
            with object == (struct rastport *) result->rastport
            and message == [ (Layer *) layer, (struct Rectangle) bounds,
                           (WORD) offsetx, (WORD) offsety ]
    bm2 - pointer to optional Super bitmap

RESULTS
    result - pointer to layer structure if successful
             NULL if not successful

BUGS

SEE ALSO
    deletelayer, graphics/layers.h, graphics/clip.h, graphics/gfx.h
    utility/hooks.h