NAME                                                              (V36)
    CreateUpfrontHookLayer -- Create a new layer on top of existing layers,
                              using supplied callback BackFill hook.

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

    struct Layer *CreateUpfrontHookLayer(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)
    and place it on top of all other layers.
    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.

    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.
    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