mirror of
https://github.com/deater/dos33fsprogs.git
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152 lines
2.3 KiB
ArmAsm
152 lines
2.3 KiB
ArmAsm
.include "zp.inc"
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;================================
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; Clear screen and setup graphics
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;================================
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jsr clear_screens ; clear top/bottom of page 0/1
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jsr set_gr_page0
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;===============
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; Init Variables
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;===============
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lda #0
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sta DISP_PAGE
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;=======================
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; decompress scroll text
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;=======================
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lda #0
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sta CV
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sta ANGLE
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lda #>sky_background
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sta INH
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lda #<sky_background
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sta INL
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jsr decompress_scroll
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scroll_forever:
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jsr scroll_background
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; lda #250
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; jsr WAIT
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jsr wait_until_keypressed
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inc ANGLE
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lda ANGLE
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and #$0f
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sta ANGLE
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jmp scroll_forever
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;===============================================
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; Routines
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;===============================================
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.include "../asm_routines/hlin_clearscreen.s"
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.include "../asm_routines/gr_scroll.s"
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.include "../asm_routines/pageflip.s"
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.include "../asm_routines/gr_setpage.s"
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.include "../asm_routines/keypress.s"
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;===============================================
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; Variables
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;===============================================
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.include "starry_sky.scroll"
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;==================
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; scroll background
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;==================
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; background already loaded
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; ANGLE 0-15 sets angle
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; CV is Y position to display at
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; 182/220... 220/16 = 13.75
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; 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
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; 0 13 27 41 55 68 82 96 110 123 137 151 165 178 192 206 220
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scroll_offsets:
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.byte 0,13,27,41,55,68,82,96,110,123,137,151,165,178,192,206
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scroll_background:
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ldy ANGLE
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lda scroll_offsets,Y
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sta OFFSET
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scrollbg_loop:
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ldx #0
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ldy CV
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lsr
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lda gr_offsets,Y ; get position
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sta bgsm1+1
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lda gr_offsets+2,Y ; get position
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sta bgsm2+1
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lda gr_offsets+4,Y ; get position
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sta bgsm3+1
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lda gr_offsets+6,Y ; get position
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sta bgsm4+1
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iny
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clc
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lda gr_offsets,Y ; get position
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adc DRAW_PAGE
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sta bgsm1+2
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lda gr_offsets+2,Y ; get position
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adc DRAW_PAGE
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sta bgsm2+2
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lda gr_offsets+4,Y ; get position
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adc DRAW_PAGE
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sta bgsm3+2
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lda gr_offsets+6,Y ; get position
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adc DRAW_PAGE
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sta bgsm4+2
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ldy OFFSET
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bgdraw_loop:
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lda scroll_row1,Y
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bgsm1:
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sta $400,X
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lda scroll_row2,Y
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bgsm2:
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sta $480,X
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lda scroll_row3,Y
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bgsm3:
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sta $500,X
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lda scroll_row4,Y
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bgsm4:
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sta $580,X
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iny
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inx
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cpx #40
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bne bgdraw_loop
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;==================
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; flip pages
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;==================
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jsr page_flip ; 6
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done_bgscrolling:
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rts
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