Stencil blitting works on the IIgs!

joeylib/src/jIIgs.asm

@@ -125,118 +125,6 @@ blitTop	ldy	source	; Load Y register with source pixel offset
 	end
 
 
-;----------------------------------------
-; Blit an 8x8 block with alpha to (almost) anywhere on a surface.
-;----------------------------------------
-asmB88ax	start
-
-source	equ	1	; Source Pixels Offset
-target	equ	3	; Target Pixels Offset
-mask	equ	5	; Mask Offset
-t	equ	7	; Temp
-xc	equ	9	; X Counter
-yc	equ	11	; Y Counter
-
-	jsubroutine (4:surface,4:tiles,2:sx,2:sy,2:tx,2:ty,2:offset),12
-	using GlobalData
-
-; Find offset into tile memory
-	lda	sx	; Multiply sx by 4 to get offset (two pixels per byte)
-	asl	a
-	asl	a
-	sta	t
-	clc
-	lda	sy	; Multiply sy by 16 to get index into scanline table
-	asl	a
-	asl	a
-	asl	a
-	asl	a	; y screen location is now in the accumulator
-	tay
-	clc
-	lda	ScTable,y	; Load byte offset of y position from table
-	adc	t	; Add t to scanline offset
-	sta	source	; Offset to start of source pixels
-
-; Find offset into tile memory for mask data
-	lda	offset	; Load offset
-	asl	a	; Multiply by 4
-	asl	a
-	clc
-	adc	source	; Add to source pixel offset
-	sta	mask	; Offset to start of mask pixels
-
-; Divide target horizontal position by two since there are two pixels per byte
-	lda	tx	; Load X target position into accumulator
-	lsr	a	; Shift Right - divide by 2
-	clc
-	sta	tx	; Store it back into tx
-
-; Find offset into target surface memory
-	lda	ty	; Load ty to get index into scanline table
-	asl	a	; Multiply by two to get offset into scanline table (two bytes per entry in table)
-	tay
-	lda	ScTable,y	; Load byte offset of y position from table
-	adc	tx	; Add x position to scanline offset
-	sta	target	; Offset to start of target pixels
-
-	lda	#0	; Load 0 into X and Y counters
-	sta	xc
-	sta	yc
-
-blitTop	ldy	target	; Load Y register with target pixel offset
-	lda	[surface],y	; Load target pixels
-	ldy	mask	; Load Y register with mask pixel offset
-	and	[tiles],y	; AND with mask
-	ldy	source	; Load Y register with source pixel offset
-	ora	[tiles],y	; OR with source pixels
-	ldy	target	; Load Y register with target pixel offset
-	sta	[surface],y	; Store 4 pixels into screen
-
-	clc		; Increment to next pixel target quad
-	lda	#2
-	adc	target
-	sta	target
-	clc		; Increment to next pixel source quad
-	lda	#2
-	adc	source
-	sta	source
-	clc		; Increment to next pixel mask quad
-	lda	#2
-	adc	mask
-	sta	mask
-
-	clc
-	lda	xc	; Increment X counter
-	adc	#1
-	sta	xc
-	cmp	#2	; End of X pixels?
-	bcc	blitTop	; Nope!
-
-	lda	#0	; Reset X counter
-	sta	xc
-	clc		; Increment target offset
-	lda	#156
-	adc	target
-	sta	target
-	clc		; Increment source offset
-	lda	#156
-	adc	source
-	sta	source
-	clc		; Increment mask offset
-	lda	#156
-	adc	mask
-	sta	mask
-	clc
-	lda	yc	; Increment Y counter
-	adc	#1
-	sta	yc
-	cmp	#8	; End of Y pixels?
-	bcc	blitTop	; Nope!
-
-	jreturn
-	end
-
-
 ;----------------------------------------
 ; Blit an 8x8 block with stencil to (almost) anywhere on a surface.
 ;----------------------------------------
@@ -285,9 +173,6 @@ maskW	equ	15	; Actual mask bytes for pixels
 	adc	tx	; Add x position to scanline offset
 	sta	target	; Offset to start of target pixels
 
-
-	brk
-
 ; Find starting stencil byte
 	clc
 	lda	sy	; Vertical cell position
@@ -307,19 +192,21 @@ stenTop	ldy	stenO	; Load byte at stencil offset
 	xba		; Shift it into the high byte
 	sta	stenB	; Put it in to the stencil byte
 
+
 ; Convert stencil byte to mask word (4 pixels)
 blitTop	ldx	#4	; How many pixels to process?
-	lda	#0	; Initially, the mask word is all zero bits
+	lda	#$ffff	; Initially, the mask word is all one bits
 	sta	maskW
 nextNib	lda	stenB	; Load stencil byte into accumulator
 	asl	a	; Shift first bit out of stencil byte into C
-	bcs	pixOn	; If C is set, we draw the pixel
+	sta	stenB	; Update stencil byte
+	bcc	pixOn	; If C is clear, we draw the pixel (opposite of the mask data)
 	lda	maskW	; Load mask word into accumulator
 	asl	a	; Shift mask word over a pixel (4 bits)
 	asl	a
 	asl	a
 	asl	a
-	and	#$fff0	; Do not draw pixel - mask it off
+;	or	#$0000	; Do not draw pixel - mask it off
 	sta	maskW	; Store updated mask word
 	jmp 	nextPix	; Start next pixel
 pixOn	lda	maskW	; Load mask word into accumulator
@@ -327,15 +214,16 @@ pixOn	lda	maskW	; Load mask word into accumulator
 	asl	a
 	asl	a
 	asl	a
-	and	#$ffff	; Draw pixel
+	ora	#$000f	; Draw pixel
 	sta	maskW	; Store updated mask word
 nextPix	dex		; Decrement pixel counter in X
 	bne	nextNib	; Not zero?  Do next nibble/pixel
 
 ; Draw four pixels
+	lda	maskW         ; Load mask word
+	xba		; Flip MSB and LSB
 	ldy	target	; Load Y register with target pixel offset
-	lda	[surface],y	; Load target pixels
+	and	[surface],y	; AND target pixels with mask word
-	and	maskW	; AND with mask word
 	ldy	source	; Load Y register with source pixel offset
 	ora	[tiles],y	; OR with source pixels
 	ldy	target	; Load Y register with target pixel offset
@@ -368,7 +256,7 @@ nextPix	dex		; Decrement pixel counter in X
 	adc	source
 	sta	source
 	clc		; Increment stencil mask offset
-	lda	#39
+	lda	#40
 	adc	stenO
 	sta	stenO
 	clc

joeylib/src/joey.h

@@ -333,7 +333,7 @@ extern void     asmPoint(jlSurfaceT target, jint16 color, jint16 x, jint16 y);
 
 // Inlined functions
 #define jlDrawBlit8x8(source, cx1, cy1, cx2, cy2)                               asmB88(_jlDrawTargetActual, source, cx1, cy1, cx2, cy2)
-#define jlDrawBlit8x8a(source, stencil, cx1, cy1, cx2, cy2)                     asmB88a(_jlDrawTargetActual, source, (byte *)stencil, cx1, cy1, cx2, cy2)
+#define jlDrawBlit8x8a(source, stencil, cx1, cy1, cx2, cy2)                     asmB88a(_jlDrawTargetActual, source, (byte *)stencil->pixels, cx1, cy1, cx2, cy2)
 #define jlDrawBlitMap(startX, startY, width, height, mapData, stride, source)   asmDrawBM(_jlDrawTargetActual, startX, startY, width, height, (byte *)mapData, stride, source)
 #define jlDrawPixelGet(x, y)                                                    asmGetPoint(_jlDrawTargetActual, x, y)
 #define jlDrawPixelSet(x, y)                                                    asmPoint(_jlDrawTargetActual, _jlDrawColorNibbles, x, y)