98 lines
1.2 KiB
ArmAsm
98 lines
1.2 KiB
ArmAsm
;===============================
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; rotate intro -- rotate screen
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;===============================
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rotate_intro:
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; init the multiply routines
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; jsr init_multiply_tables
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; first copy current screen to background
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jsr gr_copy_current_to_offscreen_40x40
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lda #0
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sta ANGLE
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sta SCALE_F
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sta FRAMEL
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lda #1
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sta SCALE_I
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rotate_loop:
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jsr rotozoom
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jsr page_flip
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; zoom out
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sec
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lda SCALE_F
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sbc #$10
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sta SCALE_F
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lda SCALE_I
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sbc #$00
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sta SCALE_I
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dec ANGLE
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lda ANGLE
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and #$1f
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sta ANGLE
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; rotate counter-clockwise
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cmp #16
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beq done_rotate
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jmp rotate_loop
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done_rotate:
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rts
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;=========================================================
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; gr_copy_current_to_offscreen 40x40
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;=========================================================
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; Copy draw page to $c00
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; Take image in DRAW_PAGE
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; Copy to $c00
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; Actually copy lines 0..39
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; Don't over-write bottom 4 lines of text
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gr_copy_current_to_offscreen_40x40:
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ldx #0
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gco_40x40_loop:
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lda gr_offsets,X
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sta OUTL
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sta INL
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lda gr_offsets+1,X
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clc
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adc DRAW_PAGE
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sta OUTH
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lda gr_offsets+1,X
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clc
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adc #$8
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sta INH
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ldy #39
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gco_40x40_inner:
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lda (OUTL),Y
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sta (INL),Y
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dey
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bpl gco_40x40_inner
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inx
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inx
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cpx #40
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bne gco_40x40_loop
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rts ; 6
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