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NAME

InstallLayerHook
safely install a new Layer->BackFill hook.(V36)

SYNOPSIS

oldhook = InstallLayerHook( layer, hook )
d0 a0 a1

struct Hook *InstallLayerHook( struct Layer *, struct Hook *);

FUNCTION

Installs a new Layer->Backfill Hook, waiting until it is safe to do so. Locks the layer while substituting the new Hook and removing the old one. If a new Hook is not provided, will install the default layer BackFill Hook.

INPUTS

layer
pointer to the layer in which to install the Backfill Hook.

hook
pointer to layer callback Hook which will be called with object == (struct RastPort *) result->RastPort and message == [ (Layer *) layer, (struct Rectangle) bounds,

(LONG) offsetx, (LONG) offsety ]

This hook should fill the Rectangle in the RastPort with the BackFill pattern appropriate for offset x/y.

If hook is LAYERS_BACKFILL, the default backfill is used for the layer. (Same as pre-2.0)

As of V39: If hook is LAYERS_NOBACKFILL, the layer will not be backfilled (NO-OP).

RESULT

oldhook
pointer to the Layer->BackFill Hook that was previously active. Returns NULL if it was the default hook. In V39, it could return 1 if there was no hook.

EXAMPLE

The following hook is a very simple example that does rather little
but gives the basis idea of what is going on.

*
* This is the code called by the layer hook...
* Note that some other setup is required for this to work, including
* the definition of the PrivateData structure (pd_...) and the
* definition of the BitMapPattern structure (bmp_...)
*
CoolHook: xdef CoolHook
movem.l d2-d7/a3-a6,-(sp) ; Save these...
move.l h_SubEntry(a0),a4 ; (my private data #1 here)
move.l h_Data(a0),a5 ; Put data into address reg
*
* Now, we do the rendering...
* Note that the layer may not be important... But it is here...
*
move.l (a1)+,a0 ; Get the layer...
*
* a1 now points at the rectangle...
*
move.l pd_GfxBase(a4),a6 ; Point at GfxBase
move.l bmp_Pattern(a5),d0; Get PatternBitMap
beq SimpleCase ; None? Simple (0) case
*
* Now do the complex case of a pattern...
*
move.l a1,a3 ; Pointer to rectangle
addq.l #8,a1 ; Get past rectangle
move.l (a1)+,d2 ; X Offset (For pattern)
move.l (a1)+,d3 ; Y Offset
;
; Whatever complex blitting you would do in the complex case
; goes here
;
*
* No bitmap, so just do the simple (0) minterm case...
*
SimpleCase: moveq.l #0,d2 ; Clear d2
move.w ra_MinX(a1),d2 ; Get X pos
*
moveq.l #0,d3
move.w ra_MinY(a1),d3 ; Get Y pos
*
moveq.l #0,d4
move.w ra_MaxX(a1),d4
sub.l d2,d4
addq.l #1,d4 ; Get X size
*
moveq.l #0,d5
move.w ra_MaxY(a1),d5
sub.l d3,d5
addq.l #1,d5 ; Get Y size
*
move.l d2,d0 ; X Source
move.l d3,d1 ; Y Source
moveq.l #0,d6 ; NULL minterm
moveq.l #-1,d7 ; FF mask
*
move.l rp_BitMap(a2),a1 ; Get bitmap
move.l a1,a0
CALLSYS BltBitMap ; Do the backfill-0
*
HookDone: movem.l (sp)+,d2-d7/a3-a6 ; Restore
rts

NOTES

The RastPort you are passed back is the same one passed to the function. You should *not* use "layered" rendering functions on this RastPort. Generally, you will wish to do BitMap operations such as BltBitMap(). The callback is a raw, low-level rendering call-back. If you need to call a rendering operation with a RastPort, make sure you use a copy of the RastPort and NULL the Layer pointer.

SEE ALSO

<graphics/clip.h>, <utility/hooks.h>