CODE NOLIST INCLUDE "exec/types.i" INCLUDE "graphics/rastport.i" INCLUDE "custom.i" LIST XREF _GfxBase XREF _LVOOwnBlitter,_LVODisownBlitter XDEF _Line,_Clear ; assembler interface ;============================================================================ ; NAME ; Line ( rp,x1,y1,x2,y2 ) ; a0 d0 d1 d2 d3 ; ; Draws a line from the current position to x2,y2 in the given RastPort. ; Current color, linepat, mask and flags are observed from the rastport info. ; The blitter must be owned before calling this routine to draw lines. ;============================================================================ _Line movem.l d1-d6/a2-a3,-(sp) movea.l rp_BitMap(a0),a1 point to the bitmap struct movea.l #_custom,a3 point to custom chips ;move.w d0,d2 get start and end points ;move.w d1,d3 ;movem.w rp_cp_x(a0),d0/d1 start positions ;movem.w d2/d3,rp_cp_x(a0) save new start position moveq.l #$0f,d4 compute ASH3-ASH0 and.w d0,d4 for preshifting bltadat sub.w d0,d2 convert X2 to deltaX sub.w d1,d3 convert Y2 to deltaY mulu.w bm_BytesPerRow(a1),d1 offset to correct bitmap row lsr.w #3,d0 convert X1 to a byte offset add.w d0,d1 now d1=offset into bitplanes ; compute the correct octant code for this line ( SUD,SUL,AUL ) and get the ; absolute value of max(deltaX, deltaY) into D2 for use as the line length. tst.w d2 bmi.s 40$ deltaX is negative ; when deltaX is positive, use the following octant generation decisions tst.w d3 if deltaY is positive bmi.s 20$ cmp.w d3,d2 ...then if deltaX > deltaY... blt.s 10$ moveq.l #OCT4,d5 ...octant=4 bra.s GotOctant 10$ moveq.l #OCT0,d5 ...else octant=0... exg d2,d3 ...and switch the delta values bra.s GotOctant 20$ neg.w d3 else deltaY = -deltaY... cmp.w d3,d2 ...if deltaX > deltaY... blt.s 30$ moveq.l #OCT6,d5 ...octant=6 bra.s GotOctant 30$ moveq.l #OCT1,d5 ...else octant=1... exg d2,d3 ...and switch the delta values bra.s GotOctant ; but when deltaX is negative, use these octant generation decisions instead 40$ neg.w d2 deltaX = -deltaX tst.w d3 if deltaY is positive... bmi.s 60$ cmp.w d3,d2 ...then if deltaX > deltaY blt.s 50$ moveq.l #OCT5,d5 ...octant=5 bra.s GotOctant 50$ moveq.l #OCT2,d5 ...else octant=2... exg d2,d3 ...and switch the delta values bra.s GotOctant 60$ neg.w d3 else deltaY = -deltaY cmp.w d3,d2 if deltaX > deltaY... blt.s 70$ moveq.l #OCT7,d5 ...octant=7 bra.s GotOctant 70$ moveq.l #OCT3,d5 ...else octant = 6... exg d2,d3 ...and switch the delta values ; gets to here with the octant code in D5 and ABS(MAX(deltaX,deltaY)) in D2 GotOctant addq.w #1,d2 *** is this right ? *** 5$ add.w d3,d3 D3 = 2Y move.w d3,d0 calculate initial error term sub.w d2,d0 D0=2Y-X bpl.s 10$ no need to set SIGN ori.w #SIGN,d5 initial term is negative so... ; we start one line further up ; this is a bit tricky, we need the start code in the top 4 bits of d5 and d4 ; but they are currently in the low 4 bits of d4. Instead of shifting them ; all the way up to position, we just rotate them around and or them in. 10$ ror.w #4,d4 move start code to top bits or.w d4,d5 need shift in both halves... ; to shift line pattern too ori.w #USEA!USEC!USED,d4 move in codes for DMA channels ; OK, let's start stuffing registers that won't change between successive blits ; so we can speed up the innner loop that draws a line in each bit plane. Make ; sure that the blitter is not busy from a previous line draw routine before ; we start storing to the registers. move.w #BBUSY,d6 20$ and.w dmaconr(a3),d6 wait for the blitter to finish bne.s 20$ still busy move.w #SETBIT!BLTPRI,dmacon(a3) give blit high priority move.w d3,bltbmod(a3) bltbmod=2Y move.w d0,d3 sub.w d2,d3 compute 2Y-2X move.w d3,bltamod(a3) bltamod=2Y-2X move.w bm_BytesPerRow(a1),bltcmod(a3) move.w bm_BytesPerRow(a1),bltdmod(a3) moveq.l #-1,d3 first and last masks = $FFFF move.l d3,bltafwm(a3) this stores to both move.w rp_LinePtrn(a0),bltbdat(a3) set up line pattern asl.w #6,d2 convert line length to bltsize addq.w #2,d2 width=2 for all line drawing move.w d5,bltcon1(a3) set up bltcon1 ; stash things that need frequent reference during the plane drawing loop move.b rp_FgPen(a0),d5 get pen color and.b rp_Mask(a0),d5 and observe mask clr.w d3 move.b bm_Depth(a1),d3 get a plane counter lea.l bm_Planes(a1),a1 point to array of plane ptrs bra.s LoopEntry ; this is the loop that draws lines in each of the required bitplanes. ; Registers are set up as follows:- ; D0 = 2Y-X ; D1 = Offset in bitplane to first word of the line ; D2 = BlitSize to start the blitter with ; D3 = plane counter ; D4 = bltcon0 ; D5 = pencolor ; A1 = pointer to bitplane pointers ; A3 = pointer to custom chips ; Notice that during the loop, the blitter can be busy drawing the last line ; segment while the CPU is setting up for the next load of stores. PlaneLoop movea.l (a1)+,a2 get next bitplane address adda.w d1,a2 start address of line move.b #$0a,d4 assume erasing (minterm = NAC) lsr.w #1,d5 shift next bit into carry bcc.s 5$ it's 0 so erase this bit move.b #$ca,d4 NAC+AB we are drawing the line 5$ move.w #BBUSY,d6 10$ and.w dmaconr(a3),d6 wait for the blitter to finish bne.s 10$ still busy move.w #$8000,bltadat(a3) put in the line bit move.l a2,bltcpth(a3) fill in line start address... move.l a2,bltdpth(a3) ...of this line move.w d0,bltaptl(a3) 2Y-X, needs reloading each use move.w d4,bltcon0(a3) store the minterm and stuff move.w d2,bltsize(a3) ZOOOOM! start the line draw LoopEntry dbra d3,PlaneLoop and do the next plane movem.l (sp)+,d1-d6/a2-a3 restore regs rts all done ;============================================================================ ; Clear( rp ) ; a0 ; ; Clears ALL bitmap memory in the given rastport. Must call OwnBlitter() ; before calling this routine (or nasty things will happen fer sure). ; This routine assumes all bitplanes are contiguous in memory!!!!!!!!!!!! ;============================================================================ _Clear movea.l #_custom,a1 point to custom chips movea.l rp_BitMap(a0),a0 get the bitmap ptr moveq.l #0,d0 moveq.l #0,d1 move.w bm_Rows(a0),d0 calculate blitsize move.b bm_Depth(a0),d1 mulu.w d1,d0 d0 = #lines to clear lsl.l #6,d0 move to correct bits move.w bm_BytesPerRow(a0),d1 get width in words lsr.w #1,d1 or.w d1,d0 d0 = bltsize reg move.w #BBUSY,d1 10$ and.w dmaconr(a1),d1 wait for blitter to finish bne.s 10$ the last operation move.w #SETBIT!BLTPRI,dmacon(a1) blitter nasty clr.l bltamod(a1) bltamod & bltbmod = 0 clr.l bltcmod(a1) bltcmod & bltdmod = 0 clr.w bltcon1(a1) no shift or anything special move.w #$01f0,bltcon0(a1) only using destination move.l bm_Planes(a0),bltdpth(a1) where we are storing to clr.w bltadat(a1) what we are storing (0's) move.w d0,bltsize(a1) start the blit rts done END