87 lines
2 KiB
ArmAsm
87 lines
2 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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SEC
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LDA dx
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SBC dy
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Mult_16 A, V + 1
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STA V
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Mult_16 dy_2, dy_2 + 1
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;; D = dy_2 - dx. (signed 16-bit)
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SEC
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LDA dy_2
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SBC dx
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STA D
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LDA dy_2 + 1
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SBC #$00
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STA D + 1
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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 + 3
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LDA V + 1
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STA case_1 + 9
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end_selfmod:
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JSR pixel_calc ;;only used first pixel. after this relative position is abused
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STA byte_to_paint
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Sub_16 btp_mem_pos, btp_mem_pos + 1, #$00, #$00, !
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;LDY #$01
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INY
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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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ROR byte_to_paint
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Add_16 btp_mem_pos, btp_mem_pos + 1, #$08, #$00,!
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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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;;If D < 0 goto case_2
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LDA D + 1
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BMI case_2
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case_1:
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Sub_16 D, D + 1, #V, #V + 1,!
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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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; C = 0 eller 1
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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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; C =0
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Add_16 D, D + 1, #dy_2, #dy_2 + 1,!
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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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