mirror of https://github.com/nmlgc/ReC98.git
30 lines
551 B
NASM
30 lines
551 B
NASM
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; Transforms the 1/16-pixel on-screen Y coordinate [sy] to its corresponding
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; VRAM line given the current scrolling offset.
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; int scroll_subpixel_y_to_vram(int sy)
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public scroll_subpixel_y_to_vram_seg1
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scroll_subpixel_y_to_vram_seg1 proc near
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@@sy = word ptr 2
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mov bx, sp
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mov ax, ss:[bx+@@sy]
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sar ax, 4
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cmp _scroll_active, 0
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jz short @@lt0?
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add ax, _scroll_line
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@@lt0?:
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or ax, ax
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jge short @@lt400?
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add ax, RES_Y
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jmp short @@ret
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@@lt400?:
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cmp ax, RES_Y
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jl short @@ret
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sub ax, RES_Y
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@@ret:
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ret 2
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scroll_subpixel_y_to_vram_seg1 endp
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