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43 lines
1.0 KiB
ArmAsm
43 lines
1.0 KiB
ArmAsm
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; 2002-06-22, Ullrich von Bassewitz
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; 2018-07-27, Greg King
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;
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; Helper function for getpixel/setpixel. Load X/Y from arguments;
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; and, check if the co-ordinates are valid. Return carry clear if so.
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;
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.include "tgi-kernel.inc"
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.import popax
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.importzp ptr1, ptr2
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.proc tgi_getset
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jsr tgi_popxy ; Pop X/Y into ptr1/ptr2
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; Are the co-ordinates out of range? First, check if any coord is negative.
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txa ; (.X = ptr2+1 from tgi_popxy)
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ora ptr1+1
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sec ; Return carry set if number is negative
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bmi @L9 ; Bail out if negative
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; Check if X is larger than the maximum x coord. If so, bail out.
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lda ptr1
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cmp _tgi_xres
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txa
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sbc _tgi_xres+1
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bcs @L9
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; Check if Y is larger than the maximum y coord.
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lda ptr2
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cmp _tgi_yres
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lda ptr2+1
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sbc _tgi_yres+1
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@L9: rts
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.endproc
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