185 lines
2.7 KiB
ArmAsm
185 lines
2.7 KiB
ArmAsm
;=================================
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; Simple Horizontal LINE
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;=================================
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; line from (x,a) to (x+y,a)
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; todo: use Carry to say if X>255
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hgr_hlin:
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; get ROW into (GBASL)
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sty xrun_save
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stx x1_save
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; X1 already in X
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; Y1 already in A ; Y1 into A
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ldy #0 ; always 0
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jsr HPOSN ; (Y,X),(A) (values stores in HGRX,XH,Y)
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; important part is row is in GBASL/GBASH
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; also shifts color for us
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; Y is already the RX1/7
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; check if narrow corner case where begin and end same block
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; if RX%7 + XRUN < 7
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ldx x1_save
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lda mod7_table,X
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clc
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adc xrun_save
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cmp #7
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bcs not_same_block
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same_block:
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; want to use MASK of left_mask (MOD7) ANDed with ~left_mask (MOD7+XRUN)
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; 4+3
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; 0000 CCCC 0000 1111
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; 0000 000C 0000 0001
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; 4000 = 80 80
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; 4400 = 81 81
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; 4800 = 83 83
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; 4C00 = 87 87
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; 5000 = 8F 8F
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; 5400 = 9F 9F
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; 5800 = BF BF
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;----
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; 5C00 = FF FF
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; 4080 = ff 81 FF 81
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; 4480 = ff 83
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; 4880 = ff 87
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lda mod7_table,X ; get x1%7
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tax ; put in X
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lda left_masks,X ; get left mask
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sta same_block_mask_smc+1
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txa ; x1%7
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clc
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adc xrun_save ; (x1%7)+xrun
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tax
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lda left_masks,X ; get left mask
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eor #$7f
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and same_block_mask_smc+1
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sta same_block_mask_smc+1
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lda (GBASL),Y
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eor HGR_BITS
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same_block_mask_smc:
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and #$dd
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eor (GBASL),Y
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sta (GBASL),Y
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rts
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not_same_block:
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; see if not starting on boundary
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; X still has X1 in it
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lda mod7_table,X
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beq draw_run
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; handle not full left border
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handle_ragged_left:
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tax
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lda (GBASL),Y
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eor HGR_BITS
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and left_masks,X
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eor (GBASL),Y
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sta (GBASL),Y
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iny ; move to next
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; adjust RUN length by 7- mod7
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txa ; load mod7
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eor #$ff
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sec
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adc #7
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eor #$ff
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sec
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adc xrun_save
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sta xrun_save
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jsr shift_colors
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; draw common
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draw_run:
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lda xrun_save
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cmp #7
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bcc draw_right ; blt
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lda HGR_BITS ; get color
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sta (GBASL),Y ; store out
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iny ; move to next block
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jsr shift_colors
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lda xrun_save ; take 7 off the run
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sec
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sbc #7
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sta xrun_save
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jmp draw_run
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; draw rightmost
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draw_right:
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beq done_hgr_hlin
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; see if not starting on boundary
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ldx xrun_save
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tax
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lda (GBASL),Y
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eor HGR_BITS
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and right_masks,X
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eor (GBASL),Y
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sta (GBASL),Y
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done_hgr_hlin:
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rts
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x1_save: .byte $00
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xrun_save: .byte $00
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right_masks:
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.byte $80,$81,$83,$87, $8F,$9F,$BF
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left_masks:
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.byte $FF,$FE,$FC,$F8, $F0,$E0,$C0
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;==========================
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; shift colors
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;==========================
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; 00000000 and 10000000 => no change (black)
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; 01111111 and 11111111 => no change? (white)
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; 01010101 => invert 00101010
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shift_colors:
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lda HGR_BITS
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asl
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cmp #$C0
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bpl done_shift_colors
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lda HGR_BITS
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eor #$7f
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sta HGR_BITS
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done_shift_colors:
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rts
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;==========================
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; set color
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;==========================
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; color in X
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set_hcolor:
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lda COLORTBL,X
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sta HGR_COLOR
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rts
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