45 lines
958 B
ArmAsm
45 lines
958 B
ArmAsm
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; Ullrich von Bassewitz, 22.06.2002
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; Helper function for getpixel/setpixel. Load X/Y from stack and check if
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; the coordinates 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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tgi_getset:
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sta ptr2 ; Y
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stx ptr2+1
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jsr popax
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sta ptr1 ; X
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stx ptr1+1
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; Are the coordinates are out of range? First check if any ccord is negative.
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txa
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ora ptr2+1
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asl a
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bcs @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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