4d12f20a6e
A new proc, line.s that can chose whitch line_* to use A small test program in source.s Wrote a smal test program in source.s (all looks good exept line_up_inv)
84 lines
1.8 KiB
ArmAsm
84 lines
1.8 KiB
ArmAsm
;;drawing line from 2 cordinates
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.proc line_up
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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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;;Not values but register position in memory
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X_end = $04
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Y_end = $05
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X_pos = $FC
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Y_pos = $FB
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dy_2 = $0607
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dx = $0c
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V = $0809
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D = $0a0b
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;;example values ~~~~~ SHOULD BE PRECOMPILED
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;LDA #$90
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;STA X_pos
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;STA Y_pos
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;LDA #$aa
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;STA X_end
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;LDA #$80
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;STA Y_end
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;;~~~~~~~~~~
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;;We need to clear this memory
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LDA #$00
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STA <V
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STA <dy_2
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STA $FD ; for pixel_draw
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;; V = 2*(dx -dy)
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;; where: dy = Y_pos - Y_end, dx = X_end - X_start
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LDA Y_pos
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SEC
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SBC Y_end
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STA >V
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STA >dy_2; >dy_2 = dy. Needed for dy_2 (not for V)
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LDA X_end
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SEC
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SBC X_pos
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STA dx
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SEC
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SBC >V
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STA >V; <V = dx - dy
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mult_16 >V, <V; V = 2*(dx -dy)
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;dy_2 = dy*2
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mult_16 >dy_2, <dy_2
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;;D = 2*dy - dx + 2*255
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;;Our D is bigger then wikipedia because D is unsigned.
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LDA >dy_2
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STA >D
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LDA <dy_2
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STA <D
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Add_16 >D, <D, #$ff, #$01
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Sub_16 >D, <D, dx, #$00
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for_x:
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jsr pixel_draw
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;;Increment X until X_pos = X_end and Y_pos = Y_end
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INC X_pos
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LDX X_pos
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CPX X_end
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BEQ end
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;;If D < %00000010 00000000: case_2
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;;else case 1.
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Lag_16 >D, <D, #$00, #$02, case_2
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case_1:
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DEC Y_pos
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Sub_16 >D, <D, >V, <V; D = D - V
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JMP for_x
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case_2:
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Add_16 >D, <D, >dy_2, <dy_2;D = D + 2*dy
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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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