ppu_scanline_foo.go

func (p *Ppu) renderTileRow() {
	// 32 total loops for 32 tiles, 1 pixel of each
	for x := 0; x < 32; x++ {
		// for i := a; i < a+0x20; i++ {
		attrAddr := 0x23C0 | (p.VramAddress & 0xC00) | int(p.AttributeLocation[p.VramAddress&0x3FF])
		shift := p.AttributeShift[p.VramAddress&0x3FF]
		attr := ((p.Vram[attrAddr] >> shift) & 0x03) << 2

		ntAddress := p.selectNametable((p.VramAddress & 0xC00) >> 10)
		t := p.bgPatternTableAddress(p.Vram[(p.VramAddress&0x3FF)+ntAddress])

		tile := p.Vram[t : t+16]

		p.decodePatternTile([]Word{tile[p.TilerowCounter], tile[p.TilerowCounter+8]}, x*8, p.Scanline, p.bgPaletteEntry(attr), nil)

		// Flip bit 10 on wraparound
		if p.VramAddress&0x1F == 0x1F {
			// If rendering is enabled, at the end of a scanline
			// copy bits 10 and 4-0 from VRAM latch into VRAMADDR
			p.VramAddress = p.VramAddress ^ (p.VramLatch & 0x41F)
		} else {
			p.VramAddress++
		}
	}

	p.TilerowCounter++

	if p.TilerowCounter == 8 {
		p.TilerowCounter = 0
	}
}