chore(ppu): move bg fetcher code into fetcher functions
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parent
2acdaaeec2
commit
38460577b9
189
src/ppu.rs
189
src/ppu.rs
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@ -170,6 +170,9 @@ impl Ppu {
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// By only running on odd cycles, we can ensure that we draw every two T cycles
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if cycle % 2 != 0 {
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let control = &self.control;
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let pos = &self.pos;
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let line_y = self.pos.line_y;
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let scroll_y = self.pos.scroll_y;
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let window_y = self.pos.window_y;
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@ -177,38 +180,17 @@ impl Ppu {
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match self.fetcher.state {
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TileNumber => {
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let scroll_x = self.pos.scroll_x;
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// Increment Window line counter if scanline had any window pixels on it
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// only increment once per scanline though
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if window_present && !self.fetcher.window_line.checked() {
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self.fetcher.window_line.increment();
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}
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// Determine which tile map is being used
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let tile_map = if window_present {
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self.control.win_tile_map_addr()
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} else {
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self.control.bg_tile_map_addr()
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};
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let tile_map_addr = tile_map.into_address();
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let x_pos = self.fetcher.x_pos;
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// Both Offsets are used to offset the tile map address we found above
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// Offsets are ANDed wih 0x3FF so that we stay in bounds of tile map memory
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// TODO: Is this necessary / important in other fetcher modes?
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let x_offset = (self.fetcher.x_pos + scroll_x) as u16 & 0x03FF;
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let y_offset = (line_y.wrapping_add(scroll_y)) as u16 & 0x03FF;
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// Scroll X Offset is only used when we're rendering the background;
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let scx_offset = if window_present { 0 } else { scroll_x / 8 } & 0x1F;
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let offset = if window_present {
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32 * (self.fetcher.window_line.count() as u16 / 8)
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} else {
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32 * (((y_offset) & 0x00FF) / 8)
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};
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let addr = tile_map_addr + offset + x_offset + scx_offset as u16;
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let addr = self
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.fetcher
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.bg_tile_num_addr(control, pos, x_pos, window_present);
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let id = self.read_byte(addr);
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self.fetcher.tile.with_id(id);
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@ -217,81 +199,26 @@ impl Ppu {
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self.fetcher.state = TileDataLow;
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}
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TileDataLow => {
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let id = self
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.fetcher
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.tile
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.id
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.expect("Tile Number unexpectedly missing");
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let addr = self.fetcher.bg_byte_low_addr(control, pos, window_present);
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let tile_data_addr = match self.control.tile_data_addr() {
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TileDataAddress::X8800 => (0x9000_i32 + (id as i32 * 16)) as u16,
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TileDataAddress::X8000 => 0x8000 + (id as u16 * 16),
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};
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let offset = if window_present {
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2 * (self.fetcher.window_line.count() % 8)
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} else {
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2 * ((line_y + scroll_y) % 8)
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};
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let addr = tile_data_addr + offset as u16;
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let low = self.read_byte(addr);
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self.fetcher.tile.with_low_byte(low);
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self.fetcher.state = TileDataHigh;
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}
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TileDataHigh => {
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let id = self
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.fetcher
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.tile
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.id
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.expect("Tile Number unexpectedly missing");
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let addr = self.fetcher.bg_byte_low_addr(control, pos, window_present);
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let tile_data_addr = match self.control.tile_data_addr() {
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TileDataAddress::X8800 => (0x9000_i32 + (id as i32 * 16)) as u16,
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TileDataAddress::X8000 => 0x8000 + (id as u16 * 16),
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};
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let offset = if window_present {
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2 * (self.fetcher.window_line.count() % 8)
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} else {
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2 * ((line_y + scroll_y) % 8)
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};
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let addr = tile_data_addr + offset as u16;
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let high = self.read_byte(addr + 1);
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self.fetcher.tile.with_high_byte(high);
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self.fetcher.state = SendToFifo;
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}
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SendToFifo => {
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if let Some(low) = self.fetcher.tile.low {
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if let Some(high) = self.fetcher.tile.high {
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let pixel = TwoBitsPerPixel::from_bytes(high, low);
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let palette = self.monochrome.bg_palette;
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if self.fifo.background.is_empty() {
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for i in 0..8 {
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// Horizontally flip pixels
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let bit = 7 - i;
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let shade = palette.colour(pixel.pixel(bit));
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let fifo_pixel = FifoPixel {
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kind: FifoPixelKind::Background,
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shade,
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palette: None,
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priority: None,
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};
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self.fifo.background.push_back(fifo_pixel);
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}
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}
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let palette = &self.monochrome.bg_palette;
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self.fetcher.send_to_fifo(&mut self.fifo, palette);
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self.fetcher.state = TileNumber;
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self.fetcher.x_pos += 1;
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}
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}
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}
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}
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}
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@ -948,6 +875,100 @@ impl PixelFetcher {
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pub fn vblank_reset(&mut self) {
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self.window_line.vblank_reset();
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}
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fn bg_tile_num_addr(
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&self,
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control: &LCDControl,
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pos: &ScreenPosition,
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x_pos: u8,
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window: bool,
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) -> u16 {
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let line_y = pos.line_y;
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let scroll_y = pos.scroll_y;
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let scroll_x = pos.scroll_x;
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// Determine which tile map is being used
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let tile_map = if window {
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control.win_tile_map_addr()
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} else {
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control.bg_tile_map_addr()
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};
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let tile_map_addr = tile_map.into_address();
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// Both Offsets are used to offset the tile map address we found above
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// Offsets are ANDed wih 0x3FF so that we stay in bounds of tile map memory
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// TODO: Is this necessary / important in other fetcher modes?
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let x_offset = (x_pos + scroll_x) as u16 & 0x03FF;
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let y_offset = (line_y.wrapping_add(scroll_y)) as u16 & 0x03FF;
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// Scroll X Offset is only used when we're rendering the background;
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let scx_offset = if window { 0 } else { scroll_x / 8 } & 0x1F;
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let offset = if window {
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32 * (self.window_line.count() as u16 / 8)
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} else {
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32 * (((y_offset) & 0x00FF) / 8)
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};
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// Determine Address
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tile_map_addr + offset + x_offset + scx_offset as u16
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}
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fn bg_byte_low_addr(
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&mut self,
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control: &LCDControl,
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pos: &ScreenPosition,
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window: bool,
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) -> u16 {
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let line_y = pos.line_y;
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let scroll_y = pos.scroll_y;
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let id = self.tile.id.expect("Tile Number unexpectedly missing");
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let tile_data_addr = match control.tile_data_addr() {
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TileDataAddress::X8800 => (0x9000_i32 + (id as i32 * 16)) as u16,
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TileDataAddress::X8000 => 0x8000 + (id as u16 * 16),
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};
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let offset = if window {
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2 * (self.window_line.count() % 8)
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} else {
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2 * ((line_y + scroll_y) % 8)
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};
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tile_data_addr + offset as u16
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}
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fn send_to_fifo(&mut self, fifo: &mut FifoRenderer, palette: &BackgroundPalette) {
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let tile_bytes = self.tile.low.zip(self.tile.high);
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if let Some(bytes) = tile_bytes {
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let low = bytes.0;
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let high = bytes.1;
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let pixel = TwoBitsPerPixel::from_bytes(high, low);
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if fifo.background.is_empty() {
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for i in 0..8 {
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// Horizontally flip pixels
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let bit = 7 - i;
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let shade = palette.colour(pixel.pixel(bit));
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let fifo_pixel = FifoPixel {
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kind: FifoPixelKind::Background,
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shade,
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palette: None,
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priority: None,
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};
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fifo.background.push_back(fifo_pixel);
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}
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}
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}
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self.x_pos += 1;
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}
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}
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#[derive(Debug, Clone, Copy, Default)]
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