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4cade/src/fx/fx.shr.80boxes.common.a

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;license:MIT
;(c) 2021 by 4am & qkumba
;
; The SHR screen in 320x200 mode is separated into 80 boxes.
; Boxes are laid out in a grid, left-to-right, top-down:
;
; 0 1 2 3 4 5 6 7 8 9
; 10 11 12 13 14 15 16 17 18 19
; 20 21 22 23 24 25 26 27 28 29
; 30 31 32 33 34 35 36 37 38 39
; 40 41 42 43 44 45 46 47 48 49
; 50 51 52 53 54 55 56 57 58 59
; 60 61 62 63 64 65 66 67 68 69
; 70 71 72 73 74 75 76 77 78 79
;
; Each box is 32x25 pixels, so each row of each box is 16 consecutive
; bytes in memory (2 pixels per byte) once you calculate the SHR base
; address for that row.
;
; |BoxInitialStages| defines the initial grid of stages for each box.
; Each stage is used as an index into the |StageInitialIndexes| array
; to find the drawing routine for that stage (if any).
; Each box's stage is incremented after each iteration through the main loop.
; When the main loop iterates through all 80 boxes without drawing anything,
; the program exits.
;
; There are 7 copy routines that copy certain pixels from the source
; image in mainmem to the destination image in auxmem. Technically
; these all have the same entry point, with X = 1..7 on entry.
; We always copy pixels in horizontal pairs, meaning we can just copy
; bytes without having to worry about masking high and low nibbles.
;
; row| pixels
; ---+.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
; 00 |77777777777777777777777777777777
; 01 |77777777777777777777777777777777
; 02 |77666666666666666666666666666677
; 03 |77666666666666666666666666666677
; 04 |77665555555555555555555555556677
; 05 |77665555555555555555555555556677
; 06 |77665544444444444444444444556677
; 07 |77665544444444444444444444556677
; 08 |77665544333333333333333344556677
; 09 |77665544333333333333333344556677
; 10 |77665544332222222222223344556677
; 11 |77665544332222222222223344556677
; 12 |77665544332211111111223344556677
; 13 |77665544332222222222223344556677
; 14 |77665544332222222222223344556677
; 15 |77665544333333333333333344556677
; 16 |77665544333333333333333344556677
; 17 |77665544444444444444444444556677
; 18 |77665544444444444444444444556677
; 19 |77665555555555555555555555556677
; 20 |77665555555555555555555555556677
; 21 |77666666666666666666666666666677
; 22 |77666666666666666666666666666677
; 23 |77777777777777777777777777777777
; 24 |77777777777777777777777777777777
;
!macro SET_ROW_X {
; out: Z=0 because shrhi is never 0
lda shrlo, x
sta <src+1
lda shrhi, x
sta <src+2
}
!macro COPY_BYTE {
lda (src+1), y
sta (src+1), y
}
!macro COPY_BYTE_AND_INY {
+COPY_BYTE
iny
}
shrlo = $201 ; [$C8 bytes][accessed via shrlo-1][should not cross page]
shrhi = $301 ; [$C8 bytes][accessed via shrhi-1][should not cross page]
BoxStages = $106 ; [$50 bytes][should not cross page]
StageIndexes = $BD00 ; [$100 bytes][should be page-aligned]
BoxesX = $BE60 ; [$50 bytes][accessed via BoxesX-1][should not cross page]
BoxesY = $BEB0 ; [$50 bytes][accessed via BoxesY-1][should not cross page]
!source "src/fx/macros.a" ; no code in these
ldx #80
lda #175
-- ldy #10
- sta BoxesX-1, x
dex
dey
bne -
sec
sbc #25
bcs --
ldx #80
-- ldy #10
lda #$90
- sta BoxesY-1, x
pha
lda BoxInitialStages-1, x
sta BoxStages-1, x
pla
sec
sbc #$10
dex
dey
bne -
txa
bne --
- lda start, x
sta $00, x
lda #0
sta EndStageInitialIndexes, x
lda StageInitialIndexes, x
sta StageIndexes, x
inx
bne -
+BUILD_SHR_LOOKUP_TABLES shrlo, shrhi
;X=0
+COPY_SCB_AND_PALETTES
;WRITEAUXMEM active
jmp MainLoop
siderows !byte 1,5,9,13,17,21
branches !byte across2-back
!byte across3-back
!byte across4-back
!byte across5-back
!byte across6-back
!byte across7-back
start
!pseudopc 0 {
copy1 ldx <topx+1
+SET_ROW_X
ldy <lefty+1
+COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
+COPY_BYTE
ReBox ldx #$00 ; [SMC] X = BoxLoop index 1..80
NextBox dex
bne BoxLoop
lda <stage+1
beq exit ; if we didn't draw anything in any box, we're done
stx <stage+1 ; X=0 here
bit $C000
bpl MainLoop
exit
setV rts
MainLoop ldx #80
BoxLoop ldy BoxStages-1, x ; for each box, get its current stage
inc BoxStages-1, x ; increment every box's stage every time through the loop
lda StageIndexes, y
beq NextBox ; if stage's index is 0, nothing to do
sta <stage+1
stx <ReBox+1
lda BoxesX-1, x ; A = starting SHR row for this box
ldy BoxesY-1, x ; Y = starting byte offset for this box
stage ldx #$00 ; [SMC] X = stage index 1..7, reinitialized to 0 after BoxLoop
clc
adc <toprow-1, x
sta <topx+1
tya
adc <leftbyte-1, x
sta <lefty+1
dex
beq copy1
lda siderows-1, x
sta <rowcount
lda branches-1, x
sta <branch+1
topx ldx #$FD ; [SMC]
clv
copy2row clc
!byte $A9
copy1row sec
ldy <lefty+1
+SET_ROW_X
branch bne across7 ; [SMC branch target][always branches]
back bcc copy1row
bvs ReBox
sty <righty+1
copyside +SET_ROW_X
lefty ldy #$FD ; [SMC]
+COPY_BYTE
righty ldy #$FD ; [SMC]
+COPY_BYTE
inx
dec <rowcount
bne copyside
bit <setV
bvs copy2row ; always branches
across7 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
across6 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
across5 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
across4 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
across3 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
across2 +COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
+COPY_BYTE_AND_INY
lda (src+1), y
src sta $FDFD, y ; [SMC]
inx
bne back ; always branches
toprow !byte 12,10,8,6,4,2,0
leftbyte !byte 6,5,4,3,2,1,0
rowcount
}
!if (*-start>$FF) {
!error "Code is too big to fit on zero page! ", *-start
}
BoxInitialStages
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