Cache OCR-negative bubbles

wechat_local_ocr.py

@@ -1126,7 +1126,7 @@ class OcrEngine:
         )
         self._message_cache: OrderedDict[
             str,
-            tuple[str, str, float, float, float],
+            tuple[str, str, float, float, float] | None,
         ] = OrderedDict()
         self._scan_count = 0
         self.last_cache_hits = 0
@@ -1202,7 +1202,7 @@ class OcrEngine:
 
     def _cache(self) -> OrderedDict[
         str,
-        tuple[str, str, float, float, float],
+        tuple[str, str, float, float, float] | None,
     ]:
         cache = getattr(self, "_message_cache", None)
         if cache is None:
@@ -1282,15 +1282,17 @@ class OcrEngine:
             bubble_crop = image.crop(
                 (bubble.x, bubble.y, bubble.right, bubble.bottom)
             )
-            key = self._cache_key(sender_crop, bubble_crop)
             sequence_signature = bubble_sequence_signature(
                 sender_crop,
                 bubble_crop,
             )
-            cached = cache.get(key)
-            if cached is not None:
+            key = sequence_signature
+            if key in cache:
+                cached = cache[key]
                 hits += 1
                 cache.move_to_end(key)
+                if cached is None:
+                    continue
                 messages.append(
                     IncomingMessage(
                         sender=cached[0],
@@ -1311,6 +1313,10 @@ class OcrEngine:
                 visual_signature=sequence_signature,
             )
             if message is None:
+                cache[key] = None
+                cache.move_to_end(key)
+                while len(cache) > OCR_MESSAGE_CACHE_SIZE:
+                    cache.popitem(last=False)
                 continue
             cache[key] = (
                 message.sender,