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Stencil blitting works on the IIgs!

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This commit is contained in:
Scott Duensing 2020-05-12 18:55:10 -05:00
parent cd094cf23a
commit 436314f3f8
2 changed files with 11 additions and 123 deletions
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132
joeylib/src/jIIgs.asm
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@ -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 maskW ; AND with mask word
and [surface],y ; AND target pixels 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

2
joeylib/src/joey.h
View file

@ -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)