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fix(ppu): fix bugs in code that grabs sprite tiles 

PPU now supports 8x16 tiles
This commit is contained in:
Rekai Nyangadzayi Musuka 2021-06-03 02:14:59 -05:00
parent 138aba52c1
commit aeaaee8c6c
1 changed files with 13 additions and 11 deletions
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24
src/ppu.rs
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@ -242,7 +242,7 @@ impl Ppu {
TileLowByte => {
let obj_size = self.control.obj_size();
let addr = PixelFetcher::get_obj_low_addr(&attr, &self.pos, obj_size);
let addr = PixelFetcher::get_obj_addr(&attr, &self.pos, obj_size);
let byte = self.read_byte(addr);
self.fetch.obj.tile.with_low_byte(byte);
@ -253,7 +253,7 @@ impl Ppu {
TileHighByte => {
let obj_size = self.control.obj_size();
let addr = PixelFetcher::get_obj_low_addr(&attr, &self.pos, obj_size);
let addr = PixelFetcher::get_obj_addr(&attr, &self.pos, obj_size);
let byte = self.read_byte(addr + 1);
self.fetch.obj.tile.with_high_byte(byte);
@ -705,22 +705,24 @@ impl PixelFetcher {
}
}
pub fn get_obj_low_addr(attr: &ObjectAttribute, pos: &ScreenPosition, size: ObjectSize) -> u16 {
pub fn get_obj_addr(attr: &ObjectAttribute, pos: &ScreenPosition, size: ObjectSize) -> u16 {
let line_y = pos.line_y;
let scroll_y = pos.scroll_y;
let tile_number = match size {
ObjectSize::Eight => attr.tile_index,
ObjectSize::Sixteen => attr.tile_index & !0x01,
// TODO: Why is the offset 14 and 30 respectively?
let (id, flip_offset) = match size {
ObjectSize::Eight => (attr.tile_index, 14),
ObjectSize::Sixteen => (attr.tile_index & !0x01, 30),
};
let offset = 2 * if attr.flags.y_flip() {
(size.as_u8() - 1) - (line_y + scroll_y) % 8
let offset = 2 * (line_y - (attr.y - 16));
let final_offset = if attr.flags.y_flip() {
flip_offset - offset
} else {
(line_y + scroll_y) % 8
offset
};
0x8000 + (tile_number as u16 * 16) + offset as u16
0x8000 + (id as u16 * 16) + final_offset as u16
}
}