Corrected OAM scan timing issue. Pixels now generated at the end of O…

…AM scan mode
TylerBloom · Oct 28, 2024 · b0e93b3 · b0e93b3
1 parent a6acd9c
commit b0e93b3
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Showing 2 changed files with 14 additions and 12 deletions.
diff --git a/spirit/src/mem/vram.rs b/spirit/src/mem/vram.rs
@@ -12,7 +12,9 @@ use serde_with::serde_as;
 use tracing::{info, trace};
 
 use super::{
-    io::{BgPaletteIndex, ObjPaletteIndex}, BgTileDataIndex, BgTileDataInnerIndex, BgTileMapAttrIndex, BgTileMapAttrInnerIndex, BgTileMapIndex, BgTileMapInnerIndex, OamObjectIndex, ObjTileDataIndex
+    io::{BgPaletteIndex, ObjPaletteIndex},
+    BgTileDataIndex, BgTileDataInnerIndex, BgTileMapAttrIndex, BgTileMapAttrInnerIndex,
+    BgTileMapIndex, BgTileMapInnerIndex, OamObjectIndex, ObjTileDataIndex,
 };
 
 static DEAD_READ_ONLY_BYTE: u8 = 0xFF;
@@ -175,7 +177,7 @@ impl Index<(ObjTileDataIndex, bool)> for VRam {
         (ObjTileDataIndex(index, bank), size): (ObjTileDataIndex, bool),
     ) -> &Self::Output {
         let bank = if bank { &self.vram[1] } else { &self.vram[0] };
-        let start = 16 * (index & (!(size as u8))) as usize;
+        let start = 16 * (if size { index & !0b1 } else { index } as usize);
         let end = start + 16 + if size { 16 } else { 0 };
         &bank[start..end]
     }
@@ -198,7 +200,10 @@ impl Index<BgTileMapInnerIndex> for VRam {
 impl Index<BgTileMapAttrInnerIndex> for VRam {
     type Output = u8;
 
-    fn index(&self, BgTileMapAttrInnerIndex { x, y, second_map }: BgTileMapAttrInnerIndex) -> &Self::Output {
+    fn index(
+        &self,
+        BgTileMapAttrInnerIndex { x, y, second_map }: BgTileMapAttrInnerIndex,
+    ) -> &Self::Output {
         let x = x as usize / 8;
         let y = y as usize / 8;
         let index = 0x1800 + (second_map as usize * 0x400) + (y * 32) + x;

diff --git a/spirit/src/ppu.rs b/spirit/src/ppu.rs
@@ -138,11 +138,8 @@ impl PpuInner {
         match self {
             PpuInner::OamScan { dots } if *dots == 79 => {
                 *self = Self::Drawing { dots: 0 };
-                mem.inc_ppu_status(self.state());
-            }
-            PpuInner::OamScan { dots } if *dots == 0 => {
                 obj.oam_scan(bg.y, mem);
-                *dots += 1;
+                mem.inc_ppu_status(self.state());
             }
             PpuInner::OamScan { dots } => *dots += 1,
             PpuInner::Drawing { dots, .. } if bg.x == 160 => {
@@ -648,11 +645,11 @@ impl OamObject {
         );
         let mut index = y - self.y;
         if check_bit_const::<6>(self.attrs) {
-            // If vertically flipped, we need to reverse the order of the bytes in the obj. Or, we
-            // need to invert our indices. We know that `index` is between 0 and 8 (or 16), so we
-            // can just mask out the upper half of the inverted index to bring it back into range.
-            let mask = if obj.len() == 32 { 0xF } else { 0x7 };
-            index = (!index) & mask;
+            index = if obj.len() == 32 {
+                15 - index
+            } else {
+                7 - index
+            };
         }
         let index = index as usize;
         let lo = obj[2 * index];