BeginUpdate() 
     BehindLayer() 
     CreateBehindHookLayer() 
     CreateBehindLayer() 
     CreateUpfrontHookLayer() 
     CreateUpfrontLayer() 
     DeleteLayer() 
     DisposeLayerInfo() 
     DoHookClipRects() 
     EndUpdate() 
     FattenLayerInfo() 
     InitLayers() 
     InstallClipRegion() 
     InstallLayerHook() 
     InstallLayerInfoHook() 
     LockLayer() 
     LockLayerInfo() 
     LockLayers() 
     MoveLayer() 
     MoveLayerInFrontOf() 
     MoveSizeLayer() 
     NewLayerInfo() 
     ScrollLayer() 
     SizeLayer() 
     SwapBitsRastPortClipRect() 
     ThinLayerInfo() 
     UnlockLayer() 
     UnlockLayerInfo() 
     UnlockLayers() 
     UpfrontLayer() 
     WhichLayer() 

    NAME
	BeginUpdate -- Prepare to repair damaged layer.

    SYNOPSIS
	result = BeginUpdate( l )
	d0                    a0

	LONG BeginUpdate( struct Layer *);

    FUNCTION
	Convert damage list to ClipRect list and swap in for
	programmer to redraw through. This routine simulates
	the ROM library environment. The idea is to only render in the
	"damaged" areas, saving time over redrawing all of the layer.
	The layer is locked against changes made by the layer library.

    INPUTS
	l - pointer to a layer

    RESULTS
	result - TRUE if damage list converted to ClipRect list successfully.
	         FALSE if list conversion aborted. (probably out of memory)

    BUGS
	If BeginUpdate returns FALSE, programmer must abort the attempt to
	refresh this layer and instead call EndUpdate( l, FALSE ) to restore
	original ClipRect and damage list.

    SEE ALSO
	EndUpdate, graphics/layers.h, graphics/clip.h

    NAME
	BehindLayer -- Put layer behind other layers.

    SYNOPSIS
	result = BehindLayer( dummy, l )
	d0                    a0     a1

	LONG BehindLayer( LONG, struct Layer *);

    FUNCTION
	Move this layer to the most behind position swapping bits
	in and out of the display with other layers.
	If other layers are REFRESH then collect their damage lists and
	set the LAYERREFRESH bit in the Flags fields of those layers that
	may be revealed.  If this layer is a backdrop layer then
	put this layer behind all other backdrop layers.
	If this layer is NOT a backdrop layer then put in front of the
	top backdrop layer and behind all other layers.

	Note: this operation may generate refresh events in other layers
	   associated with this layer's Layer_Info structure.

    INPUTS
	dummy - unused
	l - pointer to a layer

    RESULTS
	result - TRUE    if operation successful
	         FALSE   if operation unsuccessful (probably out of memory)

    BUGS

    SEE ALSO
       graphics/layers.h, graphics/clip.h

    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 (see InstallLayerHook())

	        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).

	bm2 - pointer to optional Super BitMap

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

    BUGS

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

    NAME
	CreateBehindLayer -- Create a new layer behind all existing layers.

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

	struct Layer *CreateBehindLayer(struct Layer_Info *, struct BitMap *,
	    LONG, LONG, LONG, LONG, LONG, ... );

    FUNCTION
	Create a new Layer of position and size (x0,y0)->(x1,y1)
	Make this layer of type found in flags.
	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 )
	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

    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 (see InstallLayerHook())

	        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).

	bm2 - pointer to optional Super BitMap

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

    BUGS

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

    NAME
	CreateUpfrontLayer -- Create a new layer on top of existing layers.

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

	struct Layer *CreateUpfrontLayer(struct Layer_Info *, struct BitMap *,
	    LONG, LONG, LONG, LONG, LONG, ... );

    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
	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.
	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

    NAME
	DeleteLayer -- delete layer from layer list.

    SYNOPSIS
	result = DeleteLayer( dummy, l )
	d0                    a0,    a1

	LONG DeleteLayer( LONG, struct Layer *);

    FUNCTION
	Remove this layer from the list of layers.  Release memory
	associated with it.  Restore other layers that may have been
	obscured by it.  Trigger refresh in those that may need it.
	If this is a superbitmap layer make sure SuperBitMap is current.
	The SuperBitMap is not removed from the system but is available
	for program use even though the rest of the layer information has
	been deallocated.

    INPUTS
	dummy - unused
	l - pointer to a layer

    RESULTS
	result - TRUE if this layer successfully deleted from the system
	         FALSE if layer not deleted. (probably out of memory )

    BUGS

    SEE ALSO
	graphics/layers.h, graphics/clip.h

    NAME
	DisposeLayerInfo -- Return all memory for LayerInfo to memory pool

    SYNOPSIS
	DisposeLayerInfo( li )
	                  a0

	void DisposeLayerInfo( struct Layer_Info *);

    FUNCTION
	return LayerInfo and any other memory attached to this LayerInfo
	to memory allocator.

	Note: if you wish to delete the layers associated with this Layer_Info
	    structure, remember to call DeleteLayer() for each of the layers
	    before calling DisposeLayerInfo().

    INPUTS
	li - pointer to LayerInfo structure

    EXAMPLE

	-- delete the layers associated this Layer_Info structure --

	DeleteLayer(li,simple_layer);
	DeleteLayer(li,smart_layer);

	-- see documentation on DeleteLayer about deleting SuperBitMap layers --
	my_super_bitmap_ptr = super_layer->SuperBitMap;
	DeleteLayer(li,super_layer);

	-- now dispose of the Layer_Info structure itself --
	DisposeLayerInfo(li);


    BUGS

    SEE ALSO
	DeleteLayer, graphics/layers.h

    NAME
	DoHookClipRects - Do the given hook for each of the ClipRects    (V39)

    SYNOPSIS
	DoHookClipRects(hook,rport,rect)
	                a0   a1    a2

	void DoHookClipRects(struct Hook *,struct RastPort *,struct Rectangle *);

    FUNCTION
	This function will call the given hook for each cliprect in the
	layer that can be rendered into.  This is how the backfill hook
	in Layers is implemented.  This means that hidden simple-refresh
	cliprects will be ignored.  It will call the SuperBitMap cliprects,
	smart refresh off-screen cliprects, and all on screen cliprects.
	If the rect parameter is not NULL, the cliprects are bounded to
	the rectangle given.

    INPUTS
	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.

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

	rport- A pointer to the RastPort that is to be operated on.
	       This function will lock the layer if the RastPort is
	       layered...
	       If the rport is non-layered your hook will be called with
	       the rectangle as passed, the RastPort, and a NULL layer...

	rect - The bounding rectangle that should be used on the layer.
	       This rectangle "clips" the cliprects to the bound given.
	       If this is NULL, no bounding will take place.
	       *MUST* not be NULL if the RastPort is non-layered!

    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

    NAME
	EndUpdate -- remove damage list and restore state of layer to normal.

    SYNOPSIS
	EndUpdate( l, flag )
	           a0  d0

	void EndUpdate( struct Layer *, UWORD);

    FUNCTION
	After the programmer has redrawn his picture he calls this
	routine to restore the ClipRects to point to his standard
	layer tiling. The layer is then unlocked for access by the
	layer library.

	Note: use flag = FALSE if you are only making a partial update.
	    You may use the other region functions (graphics functions such as
	    OrRectRegion, AndRectRegion, and XorRectRegion ) to clip adjust
	    the DamageList to reflect a partial update.

    INPUTS
	l - pointer to a layer
	flag - use TRUE if update was completed. The damage list is cleared.
	       use FALSE if update not complete. The damage list is retained.

    EXAMPLE

	-- begin update for first part of two-part refresh --
	BeginUpdate(my_layer);

	-- do some refresh, but not all --
	my_partial_refresh_routine(my_layer);

	-- end update, false (not completely done refreshing yet) --
	EndUpdate(my_layer, FALSE);

	-- begin update for last part of refresh --
	BeginUpdate(my_layer);

	-- do rest of refresh --
	my_complete_refresh_routine(my_layer);

	-- end update, true (completely done refreshing now) --
	EndUpdate(my_layer, TRUE);

    BUGS

    SEE ALSO
	BeginUpdate, graphics/layers.h, graphics/clip.h

    NAME
	FattenLayerInfo -- convert 1.0 LayerInfo to 1.1 LayerInfo
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    SYNOPSIS
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE
	FattenLayerInfo( li )
	                 a0

	LONG FattenLayerInfo( struct Layer_Info *);
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    FUNCTION
	V1.1 software and any later releases need to have more info in the
	Layer_Info structure. To do this in a 1.0 supportable manner requires
	allocation and deallocation of the memory whenever most
	layer library functions are called.  To prevent unnecessary
	allocation/deallocation FattenLayerInfo will preallocate the
	necessary data structures and fake out the layer library into
	thinking it has a LayerInfo gotten from NewLayerInfo.
	NewLayerInfo is the approved method for getting this structure.
	When a program needs to give up the LayerInfo structure it
	must call ThinLayerInfo before freeing the memory. ThinLayerInfo
	is not necessary if New/DisposeLayerInfo are used however.

    INPUTS
	li - pointer to LayerInfo structure

    BUGS

    SEE ALSO

	NewLayerInfo, ThinLayerInfo, DisposeLayerInfo, graphics/layers.h

    NAME
	InitLayers -- Initialize Layer_Info structure
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    SYNOPSIS
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE
	InitLayers( li )
	            a0

	void InitLayers( struct Layer_Info *);
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    FUNCTION
	Initialize Layer_Info structure in preparation to use
	other layer operations on this list of layers.
	Make the Layers unlocked (open), available to layer operations.

    INPUTS
	li - pointer to LayerInfo structure

    BUGS

    SEE ALSO
	NewLayerInfo, DisposeLayerInfo, graphics/layers.h

    NAME
	InstallClipRegion -- Install clip region in layer

    SYNOPSIS
	oldclipregion = InstallClipRegion( l,  region )
	d0                                 a0  a1

	struct Region *InstallClipRegion( struct Layer *, struct Region *);

    FUNCTION
	Installs a transparent Clip region in the layer. All
	subsequent graphics calls will be clipped to this region.
	You MUST remember to call InstallClipRegion(l,NULL) before
	calling DeleteLayer(l) or the Intuition function CloseWindow()
 	if you have installed a non-NULL ClipRegion in l.

    INPUTS
	l - pointer to a layer
	region - pointer to a region

    RESULTS
	oldclipregion - The pointer to the previous ClipRegion that
	    was installed. Returns NULL if no previous ClipRegion installed.

	    Note: If the system runs out of memory while computing the
	        resulting ClipRects the LAYERS_CLIPRECTS_LOST bit will
	        be set in l->Flags.

    BUGS
	If the system runs out of memory during normal layer operations,
	the ClipRect list may get swept away and not restored.
	As soon as there is enough memory and the layer library
	gets called again the ClipRect list will be rebuilt.

    SEE ALSO
	BeginUpdate EndUpdate,
	graphics/layers.h, graphics/clip.h, graphics/regions.h

    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).

    RESULTS
	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.

    BUGS

    SEE ALSO
	graphics/clip.h utility/hooks.h

    NAME
	InstallLayerInfoHook - Install a backfill hook for non-layer      (V39)

    SYNOPSIS
	oldhook=InstallLayerInfoHook(li,hook)
	d0                           a0 a1

	struct Hook *InstallLayerInfoHook(struct Layer_Info *,struct Hook *);

    FUNCTION
	This function will install a backfill hook for the Layer_Info
	structure passed.  This backfill hook will be used to clear the
	background area where no layer exists.  The hook function is
	passed the RastPort and the bounds just like the layer backfill
	hook.  Note that this hook could be called for any layer.

    INPUTS
	li - pointer to LayerInfo structure

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

	        This hook should fill the Rectangle in the RastPort
	        with the BackFill pattern appropriate for rectangle given.

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

		If hook is LAYERS_NOBACKFILL, there will be no
	        backfill.  (NO-OP).

    RESULTS
	oldhook - Returns the backfill hook that was in the Layer_Info.
	          Returns LAYERS_BACKFILL if the default was installed.
	          Returns LAYERS_NOBACKFILL if there was a NO-OP hook.
	          Returns -1 if there was some failure.

    EXAMPLE
	See the example in InstallLayerHook.  Note that both the Layer
	pointer and the OffsetX/Y values are not available in the
	LayerInfo backfill hook.

    NOTES
	When the hook is first installed, it is *NOT* called.  It is up
	to the application to know if it is safe to fill in the area.
	Since the hook will be called when a layer is deleted, the easiest
	way to have layers call this hook is to create and delete a backdrop
	layer that is the size of the area.

	Also, note that currently the first long word of the hook message
	contains an undefined value.  This value may look like a layer pointer.
	It is *not* a layer pointer.

	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
	InstallLayerHook

    NAME
	LockLayer -- Lock layer to make changes to ClipRects.

    SYNOPSIS
	LockLayer( dummy, l )
	           a0     a1

	void LockLayer( LONG, struct Layer *);

    FUNCTION
	Make this layer unavailable for other tasks to use.
	If another task is already using this layer then wait for
	it to complete and then reserve the layer for your own use.
	(this function does the same thing as graphics.library/LockLayerRom)

	Note: if you wish to lock MORE THAN ONE layer at a time, you
	    must call LockLayerInfo() before locking those layers and
	    then call UnlockLayerInfo() when you have finished. This
	    is to prevent system "deadlocks".

	Further Note: while you hold the lock on a layer, Intuition will block
	    on operations such as windowsizing, dragging, menus, and depth
	    arranging windows in this layer's screen.  It is recommended that
	    YOU do not make Intuition function calls while the layer is locked.

    INPUTS
	dummy - unused
	l - pointer to a layer

    BUGS

    SEE ALSO
	UnlockLayer, LockLayerInfo, UnlockLayerInfo,
	graphics.library/LockLayerRom, graphics/layers.h, graphics/clip.h

    NAME
	LockLayerInfo -- Lock the LayerInfo structure.

    SYNOPSIS
	LockLayerInfo( li )
	               a0

	void LockLayerInfo( struct Layer_Info *);

    FUNCTION
	Before doing an operation that requires the LayerInfo
	structure, make sure that no other task is also using the
	LayerInfo structure.  LockLayerInfo() returns when the
	LayerInfo belongs to this task.  There should be
	an UnlockLayerInfo for every LockLayerInfo.

	Note: All layer routines presently LockLayerInfo() when they
	start up and UnlockLayerInfo() as they exit.  Programmers
	will need to use these Lock/Unlock routines if they wish
	to do something with the LayerStructure that is not
	supported by the layer library.

    INPUTS
	li - pointer to Layer_Info structure

    BUGS

    SEE ALSO
	UnlockLayerInfo, graphics/layers.h

    NAME
	LockLayers -- lock all layers from graphics output.

    SYNOPSIS
	LockLayers( li )
	            a0

	void LockLayers( struct Layer_Info *);

    FUNCTION
	First calls LockLayerInfo()
	Make all layers in this layer list locked.

    INPUTS
	li - pointer to Layer_Info structure

    BUGS

    SEE ALSO
	LockLayer, LockLayerInfo, graphics/layers.h

    NAME
	MoveLayer -- Move layer to new position in BitMap.

    SYNOPSIS
	result = MoveLayer( dummy, l, dx, dy )
	d0                  a0     a1 d0  d1

	LONG MoveLayer( LONG, struct Layer *, LONG, LONG);

    FUNCTION
	Move this layer to new position in shared BitMap.
	If any refresh layers become revealed, collect damage and
	set REFRESH bit in layer Flags.

    INPUTS
	dummy - unused
	l - pointer to a nonbackdrop layer
	dx - delta to add to current x position
	dy - delta to add to current y position

    RETURNS
	result - TRUE if operation successful
	         FALSE if failed (out of memory)

    BUGS
	May not handle (dx,dy) which attempts to move the layer outside the
	layer's RastPort->BitMap bounds .

    SEE ALSO
	graphics/layers.h, graphics/clip.h

    NAME
	MoveLayerInFrontOf -- Put layer in front of another layer.

    SYNOPSIS
	result = MoveLayerInFrontOf( layertomove, targetlayer )
                                    a0           a1

	LONG MoveLayerInFrontOf( struct Layer *, struct Layer *);

    FUNCTION
	Move this layer in front of target layer, swapping bits
	in and out of the display with other layers.
	If this is a refresh layer then collect damage list and
	set the LAYERREFRESH bit in layer->Flags if redraw required.

	Note: this operation may generate refresh events in other layers
	    associated with this layer's Layer_Info structure.

    INPUTS
	layertomove - pointer to layer which should be moved
	targetlayer - pointer to target layer in front of which to move layer

    RESULTS
	result = TRUE    if operation successful
	         FALSE   if operation unsuccessful (probably out of memory)

    BUGS

    SEE ALSO
	graphics/layers.h

    NAME                                                              (V36)
	MoveSizeLayer -- Position/Size layer

    SYNOPSIS
	result = MoveSizeLayer( layer, dx, dy, dw, dh )
	d0                      a0     d0  d1  d2  d3

	LONG MoveSizeLayer( struct Layer *, LONG, LONG, LONG, LONG);

    FUNCTION
	Change upperleft and lower right position of Layer.

    INPUTS
	dummy - unused
	l - pointer to a nonbackdrop layer
	dx,dy - change upper left corner by (dx,dy)
	dw,dy - change size by (dw,dh)

    RETURNS
	result - TRUE if operation successful
	         FALSE if failed (due to out of memory)
	         FALSE if failed (due to illegal layer->bounds)

    BUGS

    SEE ALSO
	graphics/layers.h, graphics/clip.h

    NAME
	NewLayerInfo -- Allocate and Initialize full Layer_Info structure.

    SYNOPSIS
	result = NewLayerInfo()
	d0

	struct Layer_Info *NewLayerInfo( void );

    FUNCTION
	Allocate memory required for full Layer_Info structure.
	Initialize Layer_Info structure in preparation to use
	other layer operations on this list of layers.
	Make the Layer_Info unlocked (open).

    INPUTS
	None

    RESULT
	result- pointer to Layer_Info structure if successful
	        NULL if not enough memory

    BUGS

    SEE ALSO
	graphics/layers.h

    NAME
	ScrollLayer -- Scroll around in a superbitmap, translate coordinates
                      in non-superbitmap layer.

    SYNOPSIS
	ScrollLayer( dummy, l, dx, dy )
	             a0     a1 d0  d1

	void ScrollLayer( LONG, struct Layer *, LONG, LONG);

    FUNCTION
	For a SuperBitMap Layer:
	Update the SuperBitMap from the layer display, then copy bits
	between Layer and SuperBitMap to reposition layer over different
	portion of SuperBitMap.
	For nonSuperBitMap layers, all (x,y) pairs are adjusted by
	the scroll(x,y) value in the layer.  To cause (0,0) to actually
	be drawn at (3,10) use ScrollLayer(-3,-10). This can be useful
	along with InstallClipRegion to simulate Intuition GZZWindows
	without the overhead of an extra layer.

    INPUTS
	dummy - unused
	l - pointer to a layer
	dx - delta to add to current x scroll value
	dy - delta to add to current y scroll value

    BUGS
	May not handle (dx,dy) which attempts to move the layer outside the
	layer's SuperBitMap bounds.

    SEE ALSO
	graphics/layers.h

    NAME
	SizeLayer -- Change the size of this nonbackdrop layer.

    SYNOPSIS
	result = SizeLayer( dummy, l, dx, dy )
	d0                  a0     a1 d0  d1

	LONG SizeLayer( LONG, struct Layer *, LONG, LONG);

    FUNCTION
	Change the size of this layer by (dx,dy). The lower right hand
	corner is extended to make room for the larger layer.
	If there is SuperBitMap for this layer then copy pixels into
	or out of the layer depending on whether the layer increases or
	decreases in size.  Collect damage list for those layers that may
	need to be refreshed if damage occurred.

    INPUTS
	dummy - unused
	l - pointer to a nonbackdrop layer
	dx - delta to add to current x size
	dy - delta to add to current y size

    RESULTS
	result - TRUE if operation successful
	         FALSE if failed (out of memory)

    BUGS

    SEE ALSO
	graphics/layers.h, graphics/clip.h

    NAME
	SwapBitsRastPortClipRect -- Swap bits between common bitmap
	                            and obscured ClipRect

    SYNOPSIS
	SwapBitsRastPortClipRect( rp, cr )
	                          a0  a1

	void SwapBitsRastPortClipRect( struct RastPort *, struct ClipRect *);

    FUNCTION
	Support routine useful for those that need to do some
	operations not done by the layer library.  Allows programmer
	to swap the contents of a small BitMap with a subsection of
	the display. This is accomplished without using extra memory.
	The bits in the display RastPort are exchanged with the
	bits in the ClipRect's BitMap.

	Note: the ClipRect structures which the layer library allocates are
	actually a little bigger than those described in the graphics/clip.h
	include file.  So be warned that it is not a good idea to have
	instances of cliprects in your code.

    INPUTS
	rp - pointer to rastport
	cr - pointer to cliprect to swap bits with

    NOTE
	Because the blit operation started by this function is done asynchronously,
	it is imperative that a WaitBlit() be performed before releasing or using
	the processor to modify any of the associated structures.

    BUGS

    SEE ALSO
	graphics/clip.h, graphics/rastport.h, graphics/clip.h

    NAME
	ThinLayerInfo -- convert 1.1 LayerInfo to 1.0 LayerInfo.
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    SYNOPSIS
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE
	ThinLayerInfo( li )
	               a0

	void ThinLayerInfo( struct Layer_Info *);
	OBSOLETE OBSOLETE OBSOLETE OBSOLETE OBSOLETE

    FUNCTION
	return the extra memory needed that was allocated with
	FattenLayerInfo. This is must be done prior to freeing
	the Layer_Info structure itself. V1.1 software should be
	using DisposeLayerInfo.

    INPUTS
	li - pointer to LayerInfo structure

    BUGS

    SEE ALSO
	DisposeLayerInfo, FattenLayerInfo, graphics/layers.h

    NAME
	UnlockLayer -- Unlock layer and allow graphics routines to use it.

    SYNOPSIS
	UnlockLayer( l )
	             a0

	void UnlockLayer( struct Layer *);

    FUNCTION
	When finished changing the ClipRects or whatever you were
	doing with this layer you must call UnlockLayer() to allow
	other tasks to proceed with graphic output to the layer.

    INPUTS
	l - pointer to a layer

    BUGS

    SEE ALSO
	graphics/layers.h, graphics/clip.h

    NAME
	UnlockLayerInfo -- Unlock the LayerInfo structure.

    SYNOPSIS
	UnlockLayerInfo( li )
	                 a0

	void UnlockLayerInfo( struct Layer_Info *);

    FUNCTION
	After the operation is complete that required a LockLayerInfo,
	unlock the LayerInfo structure so that  other tasks may
	affect the layers.

    INPUTS
	li - pointer to the Layer_Info structure

     BUGS

     SEE ALSO
	LockLayerInfo, graphics/layers.h

    NAME
	UnlockLayers -- Unlock all layers from graphics output.
	                Restart graphics output to layers that have been waiting

    SYNOPSIS
	UnlockLayers( li )
	              a0

	void UnlockLayers( struct Layer_Info *);

    FUNCTION
	Make all layers in this layer list unlocked.
	Then call UnlockLayerInfo

    INPUTS
	li - pointer to the Layer_Info structure

    BUGS

    SEE ALSO
	LockLayers, UnlockLayer, graphics/layers.h

    NAME
	UpfrontLayer -- Put layer in front of all other layers.

    SYNOPSIS
	result = UpfrontLayer( dummy, l )
	d0                     a0     a1

	LONG UpfrontLayer( LONG, struct Layer *);

    FUNCTION
	Move this layer to the most upfront position swapping bits
	in and out of the display with other layers.
	If this is a refresh layer then collect damage list and
	set the LAYERREFRESH bit in layer->Flags if redraw required.
	By clearing the BACKDROP bit in the layers Flags you may
	bring a Backdrop layer up to the front of all other layers.

	Note: this operation may generate refresh events in other layers
	   associated with this layer's Layer_Info structure.

    INPUTS
	dummy - unused
	l - pointer to a nonbackdrop layer

    RESULTS
	result - TRUE   if operation successful
	         FALSE  if operation unsuccessful (probably out of memory)

    BUGS

    SEE ALSO
	graphics/layers.h

    NAME
	WhichLayer -- Which Layer is this point in?

    SYNOPSIS
	layer = WhichLayer( li, x, y )
	d0                  a0  d0 d1

	struct Layer *WhichLayer(struct Layer_Info*, WORD, WORD);

    FUNCTION
	Starting at the topmost layer check to see if this point (x,y)
	    occurs in this layer.  If it does return the pointer to this
	    layer. Return NULL if there is no layer at this point.

    INPUTS
	li  = pointer to LayerInfo structure
	(x,y) = coordinate in the BitMap

    RESULTS
	layer - pointer to the topmost layer that this point is in
	        NULL if this point is not in a layer

    SEE ALSO
	graphics/layers.h