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fix: resolve off by n * 2 when accessing Palette during BG Mode 4

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-02-01 22:56:53 -04:00
parent 48017b45f5
commit 6c7934be70
1 changed files with 10 additions and 9 deletions
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19
src/ppu.zig
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@ -50,19 +50,20 @@ pub const Ppu = struct {
std.mem.copy(u8, self.frame_buf[start..end], self.vram.buf[start..end]);
},
0x4 => {
const frame_select = io.dispcnt.frame_select.read();
const select = io.dispcnt.frame_select.read();
const vram_start = width * @as(usize, scanline);
const buf_start = vram_start * @sizeOf(u16);
const fb_start = buf_pitch * @as(usize, scanline);
const vram_start = fb_start >> 1;
const start = if (frame_select) 0xA000 + vram_start else vram_start;
const end = start + width;
const start = vram_start + if (select) 0xA000 else @as(usize, 0);
const end = start + width; // Each Entry is only a byte long
// Render Current Scanline
for (self.vram.buf[start..end]) |byte, i| {
const fb_i = i * @sizeOf(u16);
const id = byte * 2;
const j = i * @sizeOf(u16);
self.frame_buf[fb_start + fb_i + 1] = self.palette.buf[byte + 1];
self.frame_buf[fb_start + fb_i] = self.palette.buf[byte];
self.frame_buf[buf_start + j + 1] = self.palette.buf[id + 1];
self.frame_buf[buf_start + j] = self.palette.buf[id];
}
},
else => {}, // std.debug.panic("[PPU] TODO: Implement BG Mode {}", .{bg_mode}),