I was asked by Paul Firth to show how to use the graphics.library Flood()
function. This baby will flood fill areas of a RastPort with a specified
colour.

 The problem with Flood(), like some other graphics.library functions, is
the reliance on a Temporary RastPort being linked to the RastPort into
which the rendering is to be done. The Temporary RastPort, TmpRas, is used
as a scratch area by these routines.

 Intuition Windows and Screens do not have TmpRas structures linked to
their RastPorts, so we must do the job manually. A TmpRas structure is
initialised by calling InitTmpRas(), this function requires three
parameters:

	success = InitTmpRas( TmpRas, buffer, size )
	  d0                    a0      a0     d0

 TmpRas		Pointer to the TmpRas structure to initialise

 buffer		Bitplane to use for scratch

 size		Byte size of the bitplane

 Now the RKM manuals state that the bitplane used should be the same size
as one of the bitplanes in the target RastPort, so who am I to argue. In
the example program I have opened a window on the WorkBench screen, by
rights I should use the value Window->RPort->Bitmap->(BytesPerRow * Rows)
but to keep things simple I have assumed a 640*256 display as this is the
standard WorkBench size. Also, rather than allocating CHIP memory for the
buffer I have simply created space for it within the program using 

		ds.b 		(640/8)*256

 The same is true for the TmpRas structure itself, rather than allocate
memory for it, I have used:

WorkRas		rs.b		tr_SIZEOF

 This ensures that sufficient memory is available in the BSS section of the
program.

 So, to initialise the TmpRas in the example the following fragment is used:

		lea		WorkRas(a5),a0		TmpRas
		lea		ScratchBpl,a1		Buffer
		move.l		#(640/8)*256,d0		Size
		CALLGRAF	InitTmpRas		initialise it
		tst.l		d0
		beq		Error

 Once the TmpRas has been initialised it can be linked to the RastPort we
are going to render in. To do this the address of the TmpRas must be
written into the RastPort->TmpRas field. The address of the RastPort itself
is obtained from the Window structure, Window->RPort:

		move.l		win.rp(a5),a0		RastPort
		lea		WorkRas(a5),a1		TmpRas
		move.l		a1,rp_TmpRas(a0)

 We can now use the Flood() function!

 The example provided allows you to fill areas within a window with
different colours. I should point out that Flood() has two modes of
operation:

	0		Fill all adjacent pixels searching for border
	1		Fill all adjacent pixels that have same pen number

 In the example I have used mode 1, the mode being passed in register d2:

	error = Flood( RastPort, Mode, X, Y )
	 d0               a1      d2   d0 d1


 Bearing this in mind, you can now start working on a fully fledged paint
package to rival Brilliance :-)

 nb. Passing though, to draw a circle you need to call DrawEllipse() with
the horizontal radius = vertical radius. Can't remember who asked for this
titbit of information!

		DrawEllipse( RastPort, cX, cY,  a, b )
				a1     d0  d1  d2 d3

 To draw a circle:

		move.l		win.rp(a5),a1		RastPort
		move.l		x,d0			x-ord of center
		move.l		y,d1			y-ord of center
		move.l		radius,d2		a
		move.l		d2,d3			b


 That's all folks!

			M.Meany.