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feat(ppu): reimplement window line counter check

This commit is contained in:
Rekai Nyangadzayi Musuka 2021-04-30 02:09:26 -05:00
parent 51252db753
commit 11398303b5
1 changed files with 75 additions and 23 deletions
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98
src/ppu.rs
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@ -44,8 +44,9 @@ pub struct Ppu {
fifo: FifoRenderer,
obj_buffer: ObjectBuffer,
frame_buf: Box<[u8; GB_WIDTH * GB_HEIGHT * 4]>,
window_stat: WindowStatus,
x_pos: u8,
cycles: Cycle,
cycles: Cycle, // TODO: Rename this to Cycle
}
impl Ppu {
@ -154,6 +155,8 @@ impl Ppu {
}
self.scan_state.reset();
self.window_stat.set_coincidence(false);
self.stat.set_mode(PpuMode::OamScan);
}
}
@ -185,15 +188,11 @@ impl Ppu {
self.scan_state.next();
}
fn draw(&mut self, cycle: u32) {
fn draw(&mut self, _cycle: u32) {
use FetcherState::*;
let control = &self.control;
let pos = &self.pos;
let line_y = self.pos.line_y;
let window_y = self.pos.window_y;
let is_window = self.control.window_enabled() && window_y <= line_y;
let iter = &mut self.obj_buffer.iter();
let obj_attr = loop {
@ -291,15 +290,19 @@ impl Ppu {
TileNumber => {
// Increment Window line counter if scanline had any window pixels on it
// only increment once per scanline though
if is_window && !self.fetcher.bg.window_line.checked() {
if self.window_stat.should_draw() {
self.fetcher.bg.window_line.increment();
}
let x_pos = self.fetcher.x_pos;
let addr = self
.fetcher
.bg_tile_num_addr(control, pos, x_pos, is_window);
let addr = self.fetcher.bg_tile_num_addr(
control,
pos,
x_pos,
self.window_stat.should_draw(),
);
let id = self.read_byte(addr);
self.fetcher.bg.tile.with_id(id);
@ -309,7 +312,9 @@ impl Ppu {
}
ToLowByteSleep => self.fetcher.bg.next(TileLowByte),
TileLowByte => {
let addr = self.fetcher.bg_byte_low_addr(control, pos, is_window);
let addr =
self.fetcher
.bg_byte_low_addr(control, pos, self.window_stat.should_draw());
let low = self.read_byte(addr);
self.fetcher.bg.tile.with_low_byte(low);
@ -318,7 +323,9 @@ impl Ppu {
}
ToHighByteSleep => self.fetcher.bg.next(TileHighByte),
TileHighByte => {
let addr = self.fetcher.bg_byte_low_addr(control, pos, is_window);
let addr =
self.fetcher
.bg_byte_low_addr(control, pos, self.window_stat.should_draw());
let high = self.read_byte(addr + 1);
self.fetcher.bg.tile.with_high_byte(high);
@ -369,6 +376,23 @@ impl Ppu {
self.frame_buf[i..(i + rgba.len())].copy_from_slice(&rgba);
self.x_pos += 1;
// Determine whether we should draw the window next frame
if self.window_stat.coincidence()
&& self.control.window_enabled()
&& self.x_pos >= self.pos.window_x - 7
{
self.window_stat.set_should_draw(true);
self.fetcher.bg.reset();
self.fifo.background.clear();
self.fetcher.x_pos = 0;
} else {
if self.pos.line_y == self.pos.window_y {
self.window_stat.set_coincidence(true);
}
self.window_stat.set_should_draw(false);
}
}
}
}
@ -380,6 +404,7 @@ impl Ppu {
self.cycles = Cycle::new(0);
self.x_pos = 0;
self.window_stat = Default::default();
self.stat.set_mode(PpuMode::OamScan);
self.pos.line_y = 0;
@ -397,7 +422,7 @@ impl Default for Ppu {
fn default() -> Self {
Self {
vram: Box::new([0u8; VRAM_SIZE]),
cycles: 0.into(),
cycles: Cycle::new(0),
frame_buf: Box::new([0; GB_WIDTH * GB_HEIGHT * 4]),
int: Default::default(),
control: Default::default(),
@ -409,7 +434,8 @@ impl Default for Ppu {
fetcher: Default::default(),
fifo: Default::default(),
obj_buffer: Default::default(),
x_pos: Default::default(),
window_stat: Default::default(),
x_pos: 0,
}
}
}
@ -630,20 +656,18 @@ impl PixelFetcher {
// Both Offsets are used to offset the tile map address we found above
// Offsets are ANDed wih 0x3FF so that we stay in bounds of tile map memory
// TODO: Is this necessary / important in other fetcher modes?
let x_offset = (x_pos + scroll_x) as u16 & 0x03FF;
let y_offset = (line_y.wrapping_add(scroll_y)) as u16 & 0x03FF;
// Scroll X Offset is only used when we're rendering the background;
let scx_offset = if window { 0 } else { scroll_x / 8 } & 0x1F;
let offset = if window {
let scx_offset = if window { 0u16 } else { scroll_x as u16 / 8 } & 0x1F;
let y_offset = if window {
32 * (self.bg.window_line.count() as u16 / 8)
} else {
32 * (((y_offset) & 0x00FF) / 8)
(32 * (((line_y as u16 + scroll_y as u16) & 0xFF) / 8)) & 0x3FF
};
// Determine Address
tile_map_addr + offset + x_offset + scx_offset as u16
let x_offset = (x_pos as u16 + scx_offset) & 0x3FF;
let y_offset = y_offset;
tile_map_addr + x_offset + y_offset
}
fn bg_byte_low_addr(
@ -732,6 +756,7 @@ impl Fetcher for BackgroundFetcher {
fn reset(&mut self) {
self.state = FetcherState::TileNumber;
self.tile = Default::default();
}
fn pause(&mut self) {
@ -947,3 +972,30 @@ impl Default for OamScanMode {
Self::Scan
}
}
#[derive(Debug, Clone, Copy, Default)]
struct WindowStatus {
/// This will be true if WY == LY at any point in the frame thus far
coincidence: bool,
/// This will be true if the conditions which tell the PPU to start
/// drawing from the window tile map is true
should_draw: bool,
}
impl WindowStatus {
pub fn should_draw(&self) -> bool {
self.should_draw
}
pub fn coincidence(&self) -> bool {
self.coincidence
}
pub fn set_should_draw(&mut self, value: bool) {
self.should_draw = value;
}
pub fn set_coincidence(&mut self, value: bool) {
self.coincidence = value;
}
}