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fix(ppu): ensure better timings for sprite fetcher

This commit is contained in:
Rekai Nyangadzayi Musuka 2021-04-20 03:14:00 -05:00
parent db1b40fe2d
commit 4f4c867a63
1 changed files with 73 additions and 68 deletions
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49
src/ppu.rs
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@ -168,9 +168,6 @@ impl Ppu {
fn draw(&mut self, cycle: u32) {
use FetcherState::*;
// By only running on odd cycles, we can ensure that we draw every two T cycles
if cycle % 2 != 0 {
let control = &self.control;
let pos = &self.pos;
@ -180,6 +177,7 @@ impl Ppu {
// Determine whether we need to enable sprite fetching
let mut obj_attr = None;
for i in 0..self.obj_buffer.len() {
if let Some(attr) = self.obj_buffer.get(i) {
if attr.x <= (self.x_pos + 8) {
@ -194,19 +192,21 @@ impl Ppu {
}
if let Some(attr) = obj_attr {
// Run the Object Fetcher
match self.fetcher.obj.state {
TileNumber => {
if cycle % 2 != 0 {
self.fetcher.obj.tile.with_id(attr.tile_index);
self.fetcher.obj.next(TileDataLow);
}
}
TileDataLow => {
if cycle % 2 != 0 {
let obj_size = match self.control.obj_size() {
ObjectSize::EightByEight => 8,
ObjectSize::EightBySixteen => 16,
};
match self.fetcher.obj.state {
TileNumber => {
self.fetcher.obj.tile.with_id(attr.tile_index);
self.fetcher.obj.next(TileDataLow);
}
TileDataLow => {
let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size);
let byte = self.read_byte(addr);
@ -214,7 +214,14 @@ impl Ppu {
self.fetcher.obj.next(TileDataHigh);
}
}
TileDataHigh => {
if cycle % 2 != 0 {
let obj_size = match self.control.obj_size() {
ObjectSize::EightByEight => 8,
ObjectSize::EightBySixteen => 16,
};
let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size);
let byte = self.read_byte(addr + 1);
@ -222,13 +229,13 @@ impl Ppu {
self.fetcher.obj.next(SendToFifo);
}
}
SendToFifo => {
self.fetcher.obj.fifo_count += 1;
if self.fetcher.obj.fifo_count == 1 {
// Load into fifo
let tile_bytes =
self.fetcher.obj.tile.low.zip(self.fetcher.obj.tile.high);
// Load into Fifo
let tile_bytes = self.fetcher.obj.tile.low.zip(self.fetcher.obj.tile.high);
if let Some(bytes) = tile_bytes {
let low = bytes.0;
@ -258,19 +265,21 @@ impl Ppu {
self.fifo.object.push_back(fifo_pixel);
}
}
} else if self.fetcher.obj.fifo_count == 2 {
self.fetcher.bg.resume();
self.fifo.resume();
}
} else if self.fetcher.obj.fifo_count == 2 {
self.fetcher.obj.reset();
} else {
panic!("Rekai Musuka <rekai@musuka.dev> is a bad programmer");
panic!("Object FIFO Logic Error has occurred :angry:");
}
}
}
}
// By only running on odd cycles, we can ensure that we draw every two T cycles
if cycle % 2 != 0 {
if self.fetcher.bg.is_enabled() {
match self.fetcher.bg.state {
TileNumber => {
@ -316,8 +325,6 @@ impl Ppu {
self.fetcher.bg.next(TileNumber);
}
}
} else {
self.fetcher.bg.resume();
}
}
@ -339,8 +346,6 @@ impl Ppu {
self.x_pos += 1;
}
} else {
self.fifo.resume();
}
}