Detect sprite 0 hit

SirBob01 · Nov 26, 2023 · 58db1e8 · 58db1e8
1 parent 83ab1d7
commit 58db1e8
Showing 1 changed file with 16 additions and 4 deletions.
diff --git a/src/ppu.c b/src/ppu.c
@@ -553,17 +553,29 @@ void draw_dot_ppu(ppu_t *ppu) {
 
     unsigned char sp_order = 0xFF;
     for (int i = 0; i < ppu->sprite_count_latch; i++) {
+        unsigned char sprite_index = ppu->sprite_indices[i];
+        unsigned char sprite_attr = ppu->sprite_latches[i];
+
         if (ppu->sprite_counters[i] == 0) {
             bool sp_pt0 = ppu->sprite_shift[i * 2] & 0x100;
             bool sp_pt1 = ppu->sprite_shift[i * 2 + 1] & 0x100;
             unsigned char sp_color_tmp = sp_pt0 | (sp_pt1 << 1);
 
+            // Detect sprite 0 hit
+            bool collision = bg_color && sp_color_tmp;
+            bool clip_left = ppu->mask & (PPU_MASK_SHOW_BG_LEFT |
+                                          PPU_MASK_SHOW_SPRITES_LEFT);
+            if (sprite_index == 0 && collision && ppu->dot != 255 &&
+                !(ppu->dot <= 7 && clip_left)) {
+                ppu->status |= PPU_STATUS_S0_HIT;
+            }
+
             // Update palette index depending on pixel priority
-            if (ppu->sprite_indices[i] <= sp_order && sp_color_tmp) {
-                sp_palette = (ppu->sprite_latches[i] & 0x3) + 4;
+            if (sprite_index <= sp_order && sp_color_tmp) {
+                sp_order = sprite_index;
+                sp_palette = (sprite_attr & 0x3) + 4;
                 sp_color = sp_color_tmp;
-                sp_behind_bg = ppu->sprite_latches[i] & 0x20;
-                sp_order = ppu->sprite_indices[i];
+                sp_behind_bg = sprite_attr & 0x20;
             }
         }
     }