From 00ceacaf521d660c5edb27216faf632c92c77bfa Mon Sep 17 00:00:00 2001
From: Riyyi <riyyi3@gmail.com>
Date: Mon, 17 Oct 2022 15:51:16 +0200
Subject: [PATCH] Emulator: Fix pixel FIFO x-coordinate offset

---
 src/ppu.cpp | 16 +++++-----------
 src/ppu.h   |  1 +
 2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/src/ppu.cpp b/src/ppu.cpp
index 8842c32..8f0935e 100644
--- a/src/ppu.cpp
+++ b/src/ppu.cpp
@@ -49,9 +49,8 @@ void PPU::update()
 		// OAM logic goes here..
 
 		if (m_clocks_into_frame % 80 == 0) {
-			// Clear FIFOs
-			m_pixel_fifo.background = {};
-			m_pixel_fifo.oam = {};
+			// Reset FIFO
+			m_pixel_fifo = {};
 
 			m_state = State::PixelTransfer;
 		}
@@ -83,9 +82,7 @@ void PPU::update()
 		if (m_clocks_into_frame % (80 + 172 + 204) == 0) {
 			m_lcd_y_coordinate++;
 			if (m_lcd_y_coordinate == 154) {
-				m_lcd_y_coordinate = 0;
-				m_clocks_into_frame = 0;
-				m_state = State::OAMSearch;
+				resetFrame();
 			}
 		}
 
@@ -160,7 +157,8 @@ void PPU::pixelFifo()
 
 			// Read the tile map index
 			uint16_t offset = (((m_viewport_y + m_lcd_y_coordinate) / TILE_HEIGHT) * 32)
-			                  + ((m_viewport_x + m_lcd_x_coordinate) / TILE_WIDTH);
+			                  + ((m_viewport_x + m_pixel_fifo.x_coordinate) / TILE_WIDTH);
+			m_pixel_fifo.x_coordinate += 8;
 			m_pixel_fifo.tile_index = Emu::the().readMemory(bg_tile_map_address + offset) & 0xff;
 
 			// Set the tile line we're currently on
@@ -305,8 +303,4 @@ void PPU::resetFrame()
 	m_clocks_into_frame = 0;
 	m_lcd_x_coordinate = 0;
 	m_lcd_y_coordinate = 0;
-
-	// Clear FIFOs
-	m_pixel_fifo.background = {};
-	m_pixel_fifo.oam = {};
 }
diff --git a/src/ppu.h b/src/ppu.h
index 5695ba6..a88fa1a 100644
--- a/src/ppu.h
+++ b/src/ppu.h
@@ -64,6 +64,7 @@ public:
 
 		State state = State::TileIndex;
 		bool step = false;
+		uint8_t x_coordinate = 0;
 		uint8_t tile_index = 0;
 		uint8_t tile_line = 0;
 		uint8_t pixels_lsb = 0;