mirror of https://github.com/bsnes-emu/bsnes.git
55 lines
1.5 KiB
C++
55 lines
1.5 KiB
C++
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auto VDP::Background::scanline() -> void {
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state.x = 0;
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state.y = vdp.io.vcounter;
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}
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auto VDP::Background::run() -> void {
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if(state.y >= vdp.vlines()) {
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output.color = 0;
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output.palette = 0;
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output.priority = 0;
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return;
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}
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uint8 hoffset = state.x;
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if(!vdp.io.horizontalScrollLock || hoffset >= 16) hoffset += vdp.io.hscroll;
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uint8 voffset = state.y;
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if(!vdp.io.verticalScrollLock || hoffset <= 191) voffset += vdp.io.vscroll;
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uint14 nameTableAddress;
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if(vdp.vlines() == 192) {
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nameTableAddress = vdp.io.nameTableAddress << 11;
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} else {
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nameTableAddress = (vdp.io.nameTableAddress & ~1) << 11 | 0x700;
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}
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nameTableAddress += ((voffset >> 3) << 6) + ((hoffset >> 3) << 1);
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uint16 tiledata;
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tiledata = vdp.vram[nameTableAddress + 0] << 0;
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tiledata |= vdp.vram[nameTableAddress + 1] << 8;
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uint14 patternAddress = tiledata.bits(0,8) << 5;
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if(tiledata.bit(9)) hoffset ^= 7;
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if(tiledata.bit(10)) voffset ^= 7;
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output.palette = tiledata.bit(11);
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output.priority = tiledata.bit(12);
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auto index = hoffset & 7;
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patternAddress += (voffset & 7) << 2;
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output.color.bit(0) = vdp.vram[patternAddress + 0].bit(index);
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output.color.bit(1) = vdp.vram[patternAddress + 1].bit(index);
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output.color.bit(2) = vdp.vram[patternAddress + 2].bit(index);
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output.color.bit(3) = vdp.vram[patternAddress + 3].bit(index);
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state.x++;
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}
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auto VDP::Background::power() -> void {
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}
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auto VDP::Background::reset() -> void {
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memory::fill(&state, sizeof(State));
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memory::fill(&output, sizeof(Output));
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}
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