Implement sprite priority rotation

twvd · Dec 11, 2023 · 0fd4269 · 0fd4269
1 parent 74224ee
commit 0fd4269
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Showing 3 changed files with 12 additions and 6 deletions.
diff --git a/src/snes/ppu/bus.rs b/src/snes/ppu/bus.rs
@@ -144,12 +144,10 @@ where
                 }
                 // OAMADDH - OAM Address and Priority Rotation (W)
                 0x2103 => {
+                    self.oam_priority = val & 0x80 != 0;
+
                     let v = (self.oamadd.get() >> 1) & 0x00FF;
-                    let val = val & 0x83; // bit 10-14 unused
-                    if val & 0x80 != 0 {
-                        // Obj priority
-                        // TODO
-                    }
+                    let val = val & 0x01;
                     Some(self.oamadd.set((v | (val as u16) << 8) << 1))
                 }
                 // OAMDATA - OAM Data Write (W)

diff --git a/src/snes/ppu/mod.rs b/src/snes/ppu/mod.rs
@@ -145,6 +145,7 @@ pub struct PPU<TRenderer: Renderer> {
     oamadd: Cell<u16>,
     oam: [u8; OAM_SIZE],
     oam_writebuf: u8,
+    oam_priority: bool,
 
     inidisp: u8,
 
@@ -253,6 +254,7 @@ where
             oamadd: Cell::new(0),
             oam: [0; OAM_SIZE],
             oam_writebuf: 0,
+            oam_priority: false,
 
             inidisp: 0,
 

diff --git a/src/snes/ppu/render.rs b/src/snes/ppu/render.rs
@@ -145,7 +145,13 @@ where
         }
 
         for idx in 0..OAM_ENTRIES {
-            let e = self.get_oam_entry(idx);
+            let prio_idx = if self.oam_priority {
+                // Priority rotation enabled
+                (idx + self.oamadd.get() as usize) % OAM_ENTRIES
+            } else {
+                idx
+            };
+            let e = self.get_oam_entry(prio_idx);
 
             if e.priority != priority {
                 continue;