From 20059ae975b1b83c2e7e231780bbb033d3afc62c Mon Sep 17 00:00:00 2001
From: Sour <mesenemu@gmail.com>
Date: Sun, 17 Feb 2019 22:44:57 -0500
Subject: [PATCH] PPU: Basic support for rendering sprites

---
 Core/Ppu.cpp | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 Core/Ppu.h   | 15 +++++++++++--
 2 files changed, 71 insertions(+), 3 deletions(-)

diff --git a/Core/Ppu.cpp b/Core/Ppu.cpp
index 023d7b3..402ea45 100644
--- a/Core/Ppu.cpp
+++ b/Core/Ppu.cpp
@@ -162,6 +162,63 @@ void Ppu::SendFrame()
 			RenderTilemap(_layerConfig[0], 8);
 			break;
 	}
+
+	//Draw sprites
+	for(int i = 0; i < 512; i+=4) {
+		uint8_t y = _oamRam[i + 1];
+		if(y >= 225) {
+			continue;
+		}
+
+		int16_t x = _oamRam[i];
+		uint8_t tileRow = (_oamRam[i + 2] & 0xF0) >> 4;
+		uint8_t tileColumn = _oamRam[i + 2] & 0x0F;
+		uint8_t flags = _oamRam[i + 3];
+
+		uint8_t palette = (flags >> 1) & 0x07;
+		bool useSecondTable = (flags & 0x01) != 0;
+
+		//TODO: vertical, horizontal flip, priority
+
+		uint8_t highTableOffset = i >> 4;
+		uint8_t shift = ((i >> 2) & 0x03) << 1;
+
+		uint8_t highTableValue = _oamRam[0x200 | highTableOffset] >> shift;
+		bool negativeX = (highTableValue & 0x01) != 0;
+		uint8_t size = (highTableValue & 0x02) >> 1;
+
+		if(negativeX) {
+			x = -x;
+		}
+
+		for(int rowOffset = 0; rowOffset < _oamSizes[_oamMode][size][1]; rowOffset++) {
+			for(int columnOffset = 0; columnOffset < _oamSizes[_oamMode][size][0]; columnOffset++) {
+				uint8_t column = (tileColumn + columnOffset) & 0x0F;
+				uint8_t row = (tileRow + rowOffset) & 0x0F;
+				uint8_t tileIndex = (row << 4) | column;
+
+				uint16_t tileStart = ((_oamBaseAddress + (tileIndex << 4) + (useSecondTable ? _oamAddressOffset : 0)) & 0x7FFF) << 1;
+				uint16_t bpp = 4;
+				for(int i = 0; i < 8; i++) {
+					for(int j = 0; j < 8; j++) {
+						uint16_t color = 0;
+						for(int plane = 0; plane < bpp; plane++) {
+							uint8_t offset = (plane >> 1) * 16;
+							color |= (((_vram[tileStart + i * 2 + offset + (plane & 0x01)] >> (7 - j)) & 0x01) << bpp);
+							color >>= 1;
+						}
+
+						if(color != 0) {
+							uint16_t paletteRamOffset = 256 + ((palette * (1 << bpp) + color) * 2);
+
+							uint16_t paletteColor = _cgram[paletteRamOffset] | (_cgram[paletteRamOffset + 1] << 8);
+							_currentBuffer[(y + i + rowOffset * 8) * 256 + x + j + columnOffset * 8] = paletteColor;
+						}
+					}
+				}
+			}
+		}
+	}
 	
 	_console->GetNotificationManager()->SendNotification(ConsoleNotificationType::PpuFrameDone);
 	_currentBuffer = _currentBuffer == _outputBuffers[0] ? _outputBuffers[1] : _outputBuffers[0];
@@ -200,7 +257,7 @@ void Ppu::Write(uint32_t addr, uint8_t value)
 		case 0x2101:
 			_oamMode = (value & 0xE0) >> 5;
 			_oamBaseAddress = (value & 0x07) << 13;
-			_oamAddressOffset = (value & 0x18) << 9;
+			_oamAddressOffset = (((value & 0x18) >> 3) + 1) << 12;
 			break;
 
 		case 0x2102:
diff --git a/Core/Ppu.h b/Core/Ppu.h
index 748db9d..b4fa71d 100644
--- a/Core/Ppu.h
+++ b/Core/Ppu.h
@@ -13,6 +13,17 @@ public:
 	constexpr static uint32_t VideoRamSize = 0x10000;
 
 private:
+	constexpr static const uint8_t _oamSizes[8][2][2] = {
+		{ { 1, 1 }, { 2, 2 } }, //8x8 + 16x16
+		{ { 1, 1 }, { 4, 4 } }, //8x8 + 32x32
+		{ { 1, 1 }, { 8, 8 } }, //8x8 + 64x64
+		{ { 2, 2 }, { 4, 4 } }, //16x16 + 32x32
+		{ { 2, 2 }, { 8, 8 } }, //16x16 + 64x64
+		{ { 4, 4 }, { 8, 8 } }, //32x32 + 64x64
+		{ { 2, 4 }, { 4, 8 } }, //16x32 + 32x64
+		{ { 2, 4 }, { 4, 4 } }  //16x32 + 32x32
+	};
+
 	shared_ptr<Console> _console;
 	shared_ptr<InternalRegisters> _regs;
 
@@ -36,8 +47,8 @@ private:
 	uint16_t *_currentBuffer;
 
 	uint8_t _oamMode = 0;
-	uint8_t _oamBaseAddress = 0;
-	uint8_t _oamAddressOffset = 0;
+	uint16_t _oamBaseAddress = 0;
+	uint16_t _oamAddressOffset = 0;
 
 	uint8_t _oamRam[Ppu::SpriteRamSize];
 	uint16_t _oamRamAddress = 0;