PR#3
PREFIX /A2OSX.BUILD
LOMEM $A00
INC 1
AUTO 6
				.LIST OFF	
*--------------------------------------
* BitBlt
*  S.CB.X1 : SrcX1 in bitmap/mask
*  S.CB.Y1 : SrcY1
*  S.CB.X2 : SrcX2
*  S.CB.Y2 : SrcY2

*  S.CB.DestX : Destination X (screen)
*  S.CB.DestY : Destination Y (screen)

*  S.CB.SrcPtr : pointer to S.BM
*  S.CB.DstPtr : pointer to Save Buffer 
*--------------------------------------
BITBLT			>LDYA CB.CACHE+S.CB.SrcPtr
				>STYA ZPBMDataPtr
				
				ldy #S.BM-1

.1				lda (ZPBMDataPtr),y
				sta BM.Cache,y
				dey
				bpl .1
				
				lda ZPBMDataPtr
				clc
				adc BM.Cache+S.BM.MASK.OFS
				sta ZPBMMaskPtr
				lda ZPBMDataPtr+1
				adc BM.Cache+S.BM.MASK.OFS+1
				sta ZPBMMaskPtr+1
				
				lda ZPBMDataPtr
				clc
				adc #S.BM
				sta ZPBMDataPtr
				bcc .2
				
				inc ZPBMDataPtr+1
	
.2				>LDYA CB.Cache+S.CB.Y1
				ldx BM.Cache+S.BM.RowBytes
				
				jsr YAMultX
				
				pha
				tya
				clc
				adc ZPBMDataPtr
				sta BLT.BMDataPtr
				pla
				pha
				adc ZPBMDataPtr+1
				sta BLT.BMDataPtr+1
				
				tya
				adc ZPBMMaskPtr
				sta BLT.BMMaskPtr
				pla 
				adc ZPBMMaskPtr+1
				sta BLT.BMMaskPtr+1
				
				lda CB.Cache+S.CB.X1
				pha
				and #7
				sta BLT.BMBitOfs
				pla
				
				lsr CB.Cache+S.CB.X1+1
				ror
				lsr CB.Cache+S.CB.X1+1
				ror
				lsr CB.Cache+S.CB.X1+1
				ror
				
				pha
				clc
				adc BLT.BMDataPtr
				sta BLT.BMDataPtr
				bcc .3

				inc BLT.BMDataPtr+1

.3				pla
				adc BLT.BMMaskPtr
				sta BLT.BMMaskPtr
				bcc .4
				
				inc BLT.BMMaskPtr+1
				
.4				lda CB.Cache+S.CB.X2
				sec
				sbc CB.Cache+S.CB.X1
				sta BLT.DX
				
				lda CB.Cache+S.CB.X2+1
				sbc CB.Cache+S.CB.X1+1
				sta BLT.DX+1
				
				>LDYA CB.Cache+S.CB.DestX
				jsr LBUF.SetBounds1YA
				stx BLT.SCRBitOfs
				
				lda CB.Cache+S.CB.DestX
				clc
				adc BLT.DX
				tay
				lda CB.Cache+S.CB.DestX+1
				adc BLT.DX+1
				jsr LBUF.SetBounds2YA
				
				lda CB.Cache+S.CB.Y2
				sec
				sbc CB.Cache+S.CB.Y1
				inc
				sta BLT.DY
				
				ldx BLT.SCRBitOfs
				beq BITBLT.LOOP
				
				ldy Shift.L.LO,x		X = 1->6
				sty ZPScrShiftPtr
				ldy Shift.L.HI,x		X = 1->6
				sty ZPScrShiftPtr+1
				
BITBLT.LOOP		>LDYA BLT.BMDataPtr
				>STYA ZPBMDataPtr
				>LDYA BLT.BMMaskPtr
				>STYA ZPBMMaskPtr

				lda BLT.BMBitOfs
				sta BLT.BMBitOfsL
				stz BLT.BMIdx
				
				ldx LBUF.C1
				stx BLT.ScrColIdx
				stz LBUF.DATA,x			make sure C1 not ORed with trash in "ora LBUF.DATA,x"	

				ldx BLT.SCRBitOfs
				bne .2
				
*------------  Shift 0

.1				jsr BLT.Get7BMDBits		we have 0xxxxxxxx in A

				ldx BLT.ScrColIdx
				sta LBUF.DATA,x
				inc BLT.ScrColIdx
				cpx LBUF.C2
				bne .1
				
				bra BITBLT.DRAW

*------------  Shift 1->6				Comment : SCRBitOfs=X=3
				
.2				lda Shift7BitsCol1,x	get #%00001111, BM bits that go in Col1
				sta .4+1
				lda Shift7BitsCol2,x	get #%01110000, BM bits that go in Col2
				sta .5+1

.3				jsr BLT.Get7BMDBits		we have c6543210 in A, destination : COL=3210xxx, COL+1=xxxx654
				
				pha						save BM byte for 2nd col
				
.4				and #$ff				SELF MODIFIED : MASK WITH #%00001111, keep col1 bits only
				tay
				
				lda (ZPScrShiftPtr),y	make 0000dddd Shift left 3 :  0dddd000
				
				ldx BLT.ScrColIdx		Get actual COL index
				ora LBUF.DATA,x			Light proper bits : 0dddd???
				sta LBUF.DATA,x			store  0xdddd???
				
				pla						Get back BM Byte
				
.5				and #$ff				SELF MODIFIED : #%01110000 get only col2 bites 
				tay
				
				lda (ZPScrShiftPtr),y	shift right 4 (=shift left 3!!!) : 00000ddd
				
				sta LBUF.DATA+1,x
				
				inx
				stx BLT.ScrColIdx
				cpx LBUF.C2
				bne .3
				
BITBLT.DRAW		ldy CB.Cache+S.CB.DestY
				jsr LBUF.DrawAtY
				inc CB.Cache+S.CB.DestY
				
				lda BLT.BMDataPtr
				clc
				adc BM.Cache+S.BM.RowBytes
				sta BLT.BMDataPtr
				bcc .6
				
				inc BLT.BMDataPtr+1
				
.6				lda BLT.BMMaskPtr
				clc
				adc BM.Cache+S.BM.RowBytes
				sta BLT.BMMaskPtr
				bcc .7
				
				inc BLT.BMMaskPtr+1
				
.7				dec BLT.DY
				beq .8
				jmp BITBLT.LOOP

.8				clc
				rts
*--------------------------------------
* BMD/BMM bits :
* 76543210 76543210
*    ^
*  BMBitOfsL (0->7)
* LBUF DATA/MASK Bits
* c6543210 c6543210
*      ^
*  SCRBitOfs  (0->6)
*--------------------------------------
BLT.Get7BMDBits	ldy BLT.BMIdx
				lda (ZPBMDataPtr),y

				ldx BLT.BMBitOfsL
				beq BLT.Get7BMBits0		OFS=0, done! and no need to advance ZPBMDataPtr
				lsr						OFS=1->7, shift one (Range 0->127)
				dex						OFS 0->6
				beq BLT.Get7BMBits1		OFS was 1....done and go to next byte, OFS=0
				
				ldy Shift.R.LO,x		X = 1->6
				sty ZPBMShiftPtr
				
				ldy Shift.R.HI,x		X = 1->6
				sty ZPBMShiftPtr+1
				
				and Mask7BitsH,x		Get only left upper X bits
				tay						xxxxx000
				
				lda (ZPBMShiftPtr),y		shift'em RIGHT 000xxxxx
				pha
				
				inc BLT.BMIdx			Next BM data byte
				
				ldy BLT.BMIdx
				lda (ZPBMDataPtr),y		get next byte

				and Mask7BitsL,x		only first Y bits 000000yy	
				tay
				
				pla						get back right part bits 000xxxxx
				
				ora (ZPBMShiftPtr),y			shift right 000000yy and ORA with 000xxxxx=0yyxxxxx
				
				dec BLT.BMBitOfsL		X = 1->6, ADD 7 MOD 8.....
				rts

BLT.Get7BMBits0	and #%01111111			Get only 7 needed bits
				ldx #7
				stx BLT.BMBitOfsL		Was 0, add 7 bits
				rts
				
BLT.Get7BMBits1	stz BLT.BMBitOfsL		Was 1, add 7 bits, MOD 8=0
				inc BLT.BMIdx			go to next byte in BM line
				rts 					LSR did already 0xxxxxxx
*--------------------------------------
MAN
SAVE /A2OSX.SRC/DRV/DHGR.DRV.S.RECT
LOAD /A2OSX.SRC/DRV/DHGR.DRV.S
ASM