mirror of https://github.com/bsnes-emu/bsnes.git
81 lines
2.3 KiB
C++
81 lines
2.3 KiB
C++
auto VDP::Background::isWindowed(uint x, uint y) -> bool {
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if((x < io.horizontalOffset) ^ io.horizontalDirection) return true;
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if((y < io.verticalOffset ) ^ io.verticalDirection ) return true;
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return false;
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}
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auto VDP::Background::updateHorizontalScroll(uint y) -> void {
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if(id == ID::Window) return;
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uint15 address = io.horizontalScrollAddress;
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static const uint mask[] = {0u, 7u, ~7u, ~0u};
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address += (y & mask[io.horizontalScrollMode]) << 1;
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address += id == ID::PlaneB;
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state.horizontalScroll = vdp.vram.read(address).bits(0,9);
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}
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auto VDP::Background::updateVerticalScroll(uint x) -> void {
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if(id == ID::Window) return;
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auto address = (x >> 4 & 0 - io.verticalScrollMode) << 1;
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address += id == ID::PlaneB;
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state.verticalScroll = vdp.vsram.read(address);
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}
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auto VDP::Background::nametableAddress() -> uint15 {
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if(id == ID::Window && vdp.screenWidth() == 320) return io.nametableAddress & ~0x0400;
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return io.nametableAddress;
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}
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auto VDP::Background::nametableWidth() -> uint {
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if(id == ID::Window) return vdp.screenWidth() == 320 ? 64 : 32;
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return 32 * (1 + io.nametableWidth);
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}
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auto VDP::Background::nametableHeight() -> uint {
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if(id == ID::Window) return 32;
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return 32 * (1 + io.nametableHeight);
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}
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auto VDP::Background::scanline(uint y) -> void {
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updateHorizontalScroll(y);
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}
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auto VDP::Background::run(uint x, uint y) -> void {
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updateVerticalScroll(x);
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bool interlace = vdp.io.interlaceMode == 3;
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if(interlace) y = y << 1 | vdp.state.field;
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x -= state.horizontalScroll;
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y += state.verticalScroll;
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uint tileX = x >> 3 & nametableWidth() - 1;
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uint tileY = y >> 3 + interlace & nametableHeight() - 1;
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auto address = nametableAddress();
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address += (tileY * nametableWidth() + tileX) & 0x0fff;
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uint pixelX = x & 7;
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uint pixelY = y & 7 + interlace * 8;
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uint16 tileAttributes = vdp.vram.read(address);
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uint15 tileAddress = tileAttributes.bits(0,10) << 4 + interlace;
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if(tileAttributes.bit(11)) pixelX ^= 7;
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if(tileAttributes.bit(12)) pixelY ^= 7 + interlace * 8;
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tileAddress += pixelY << 1 | pixelX >> 2;
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uint16 tileData = vdp.vram.read(tileAddress);
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uint4 color = tileData >> (((pixelX & 3) ^ 3) << 2);
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output.color = color ? tileAttributes.bits(13,14) << 4 | color : 0;
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output.priority = tileAttributes.bit(15);
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}
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auto VDP::Background::power() -> void {
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io = {};
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state = {};
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}
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