7f56f90613
This was recomended by dicander and duunqnd because A =$ABAC looks like one address and not 2 zero-page addresses.
78 lines
1.9 KiB
ArmAsm
78 lines
1.9 KiB
ArmAsm
;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
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;;drawing line from 2 cordinates
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;;# * (X_end, Y_end) #
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;;# #
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;;# * #
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;;# * #
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;;# (X_pos, Y_pos) #
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;;
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;;NOTE THAT X_pos <= X_end, Y_pos >= Y_end. Max 45deg!
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.proc line_up
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;; Look at line_down for referense
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.include "line.inc"; Defines memory positions, ex X_pos
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LDA #$00
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STA V + 1
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STA dy_2 + 1
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STA $FD
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SEC
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LDA dx
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SBC dy
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STA V
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Mult_16 V, V + 1
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Mult_16 dy_2, dy_2 + 1
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Mov_16 D, D + 1, dy_2, dy_2 + 1
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Add_16 D, D + 1, #$ff, #$01, !
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Sub_16 D, D + 1, dx, #$00
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selfmod:
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LDA dy_2
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STA case_2 + 1
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LDA dy_2 + 1
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STA case_2 + 7
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LDA V
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STA case_1 + 1
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LDA V + 1
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STA case_1 + 7
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end_selfmod:
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jsr pixel_draw
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Sub_16 btp_mem_pos, btp_mem_pos + 1, #$01, #$00 ;; Y has always a offset of at least 1
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LDY #$01
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LDX dx
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for_x:
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LDA byte_to_paint
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ORA (btp_mem_pos), Y
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STA (btp_mem_pos), Y
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increment_pixel_x:
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LSR byte_to_paint
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BCC increment_pixel_x_end
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move_8px_left:
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Add_16 btp_mem_pos, btp_mem_pos + 1, #$07, #$00,!
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LDA #%10000000
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STA byte_to_paint
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increment_pixel_x_end:
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DEX
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;CPX X_end
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BEQ end
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Lag_16 D, D + 1, #$00, #$02, case_2
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case_1:
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Sub_16_A D, D + 1, #>V, #<V,!
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decrement_y_pos:
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DEY
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BNE for_x
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move_8px_up:
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LDY #$08
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Sub_16 btp_mem_pos, btp_mem_pos + 1, #$40, #$01, !
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jmp for_x
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decrement_y_pos_end:
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case_2:
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Add_16 D, D + 1, #>dy_2, #<dy_2,!
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JMP for_x
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end:
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RTS
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.endproc
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