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Docs » Autodocs » layers.library » InstallLayerHook
InstallLayerHook -- safely install a new Layer->BackFill hook. (V36)
oldhook = InstallLayerHook( layer, hook )
d0 a0 a1
struct Hook *InstallLayerHook( struct Layer *, struct Hook *);
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.
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).
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.
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
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.
graphics/clip.h utility/hooks.h
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