some fixes and improvements

python_app/gui/app_window.py

@@ -169,14 +169,15 @@ class AppWindow(
 
     def _init_history_state(self) -> None:
         """Initialize runtime history buffers and render-cache state."""
-        history_limit = self._history_limit_from_config()
-        self._raw_history: deque[SweepCollection] = deque(maxlen=history_limit)
-        self._pre_history: deque[SweepCollection] = deque(maxlen=history_limit)
-        self._result_history: deque[ResultCollection] = deque(maxlen=history_limit)
+        bscan_history_limit = self._history_limit_from_config()
+        save_history_limit = self._save_history_limit_from_config()
+        self._raw_history: deque[SweepCollection] = deque(maxlen=save_history_limit)
+        self._pre_history: deque[SweepCollection] = deque(maxlen=save_history_limit)
+        self._result_history: deque[ResultCollection] = deque(maxlen=save_history_limit)
 
         # Sequence id must survive GUI restarts so history commands stay monotonic.
         self._history_command_seq = self._load_history_command_seq(self._live_config_writer.path)
-        self._bscan_history_limit = history_limit
+        self._bscan_history_limit = bscan_history_limit
         self._bscan_history_by_combo = {}
         self._bscan_depth_axis_by_combo = {}
         self._bscan_history_floor_collection_id = 0
@@ -200,15 +201,12 @@ class AppWindow(
         self._radar_limits: dict[str, float | int] | None = None
 
     def _history_limit_from_config(self) -> int:
-        """Return unified GUI history limit derived from configured ring capacities."""
-        return max(
-            1,
-            min(
-                int(self._defaults_config.rings.raw_tap.capacity),
-                int(self._defaults_config.rings.preprocessed_tap.capacity),
-                int(self._defaults_config.rings.results.capacity),
-            ),
-        )
+        """Return B-scan render history limit derived from configured ring capacities."""
+        return self._history_limit_for_config(self._defaults_config)
+
+    def _save_history_limit_from_config(self) -> int:
+        """Return maxlen for GUI snapshot-save deques (independent of ring capacities)."""
+        return self._save_history_limit_for_config(self._defaults_config)
 
     def _init_runtime_limits(self) -> None:
         """Initialize read/drain loop limits used by polling and snapshot code."""