feat: add load error signaling and comparison validation

src/pygui/backend/controllers/session_controller.py

@@ -35,6 +35,7 @@ class SessionController(QObject):
     recordingChanged = Signal()
     sensorsChanged = Signal()
     loadedFileChanged = Signal()
+    loadFileError = Signal(str)  # emitted when loadFile() fails, so QML can show why
     clusterAveragingEnabledChanged = Signal()
     settingsChanged = Signal()  # emitted when session state changes that should be persisted
     liveStatsChanged = Signal()  # emitted when receivedCount or errorCount change
@@ -275,17 +276,30 @@ class SessionController(QObject):
             try:
                 data, _ = ZWaferParser().parse(file_path)
             except (ValueError, KeyError) as exc:
-                log.warning("Could not parse %s: %s", file_path, exc)
+                msg = f"Could not parse {Path(file_path).name}: {exc}"
+                log.warning("%s", msg)
+                self.loadFileError.emit(msg)
                 return
             if data is None or not data.sensors:
-                log.warning("Could not parse %s", file_path)
+                msg = f"Could not parse {Path(file_path).name}"
+                log.warning("%s", msg)
+                self.loadFileError.emit(msg)
                 return
             records = read_data_records(file_path)
             sensors = data.sensors
             frames = frames_from_wafer_data(data, records)
 
-        if not sensors or not frames:
+        if not sensors:
-            log.warning("No sensors or data in %s", file_path)
+            msg = f"No sensor layout found in {Path(file_path).name}"
+            log.warning("%s", msg)
+            self.loadFileError.emit(msg)
+            return
+        if not frames:
+            # A well-formed header with zero data rows below it — most commonly
+            # a live recording that was stopped before any frames arrived.
+            msg = f"{Path(file_path).name} has no recorded frames"
+            log.warning("%s", msg)
+            self.loadFileError.emit(msg)
             return
 
         wafer_id = ""
@@ -304,6 +318,10 @@ class SessionController(QObject):
         self._model.reset()
         self._stats_tracker.reset()
         self._loaded_file = file_path
+        # A file was explicitly picked for review — show it regardless of
+        # whichever mode (e.g. Live) was previously active, otherwise a
+        # successful load can be invisible to the user.
+        self.setMode(MODE_REVIEW)
         self.loadedFileChanged.emit()
         self.sensorsChanged.emit()
         self._emit_current()
@@ -330,10 +348,48 @@ class SessionController(QObject):
     @slot_error_boundary
     def compareFiles(self, file_a: str, file_b: str) -> None:
         """Run DTW comparison between two CSV files and emit result."""
+        from pathlib import Path
+
         from pygui.backend.comparison import compare_runs
         from pygui.backend.data.data_records import is_official_csv, read_data_records, read_official_csv
 
         try:
+            # Recorded-live CSVs are named "live_<serial>_<timestamp>.csv" by
+            # startRecording (see FileBrowser.isRecording), distinct from the
+            # "<serial>-<timestamp>.csv" convention used for read-memory dumps.
+            # Comparing across those categories doesn't make sense (a live
+            # capture vs. a full memory readout aren't the same kind of run),
+            # so gate on that before even looking at wafer type.
+            stem_a, stem_b = Path(file_a).stem, Path(file_b).stem
+            is_recording_a = stem_a.lower().startswith("live_")
+            is_recording_b = stem_b.lower().startswith("live_")
+            if is_recording_a != is_recording_b:
+                self.comparisonResult.emit({
+                    "success": False,
+                    "error": "Cannot compare a recording file with a read-memory file"
+                })
+                return
+
+            # Gate on wafer type (family): comparing a P-wafer against an X-wafer
+            # (different sensor counts/layouts) would silently truncate the
+            # smaller sensor set and pair up unrelated physical sensors in the
+            # overlap view. Same convention as FileBrowser's waferType badge —
+            # first character of the filename stem, minus the "live_" prefix
+            # so the wafer letter is read from the serial, not the "L".
+            def _wafer_type(stem: str, is_recording: bool) -> str:
+                if is_recording:
+                    stem = stem[len("live_"):]
+                return stem[0].upper() if stem else ""
+
+            type_a = _wafer_type(stem_a, is_recording_a)
+            type_b = _wafer_type(stem_b, is_recording_b)
+            if type_a and type_b and type_a != type_b:
+                self.comparisonResult.emit({
+                    "success": False,
+                    "error": f"Cannot compare different wafer types: {type_a} vs {type_b}"
+                })
+                return
+
             if is_official_csv(file_a):
                 _, recs_a = read_official_csv(file_a)
             else:
@@ -350,8 +406,10 @@ class SessionController(QObject):
                 })
                 return
 
-            # Use first 100 frames of each for comparison (avoid O(n²) blowup)
+            # Compare the full overlapping length of both runs. DTW's O(n*m) cost
-            max_frames = min(100, len(recs_a), len(recs_b))
+            # matrix is cheap even at a few thousand frames (~26MB at 1800x1800),
+            # so only cap against pathologically long files, not typical runs.
+            max_frames = min(5000, len(recs_a), len(recs_b))
             series_a = [recs_a[i].values[0] if recs_a[i].values else 0.0
                        for i in range(max_frames)]
             series_b = [recs_b[i].values[0] if recs_b[i].values else 0.0
@@ -380,10 +438,8 @@ class SessionController(QObject):
                         max_sensor_deviation = diff
 
             # Sensor layout + per-sensor diff for the wafer overlap view. Reuses the
-            # same sensor-parsing branch as loadFile() (file_a is assumed representative
+            # same sensor-parsing branch as loadFile(); file_a and file_b are now
-            # of both files' wafer type).
+            # guaranteed to share a wafer type by the gate above.
-            from pathlib import Path
-
             from pygui.backend.data.data_records import is_official_csv, read_official_csv
             from pygui.backend.wafer.wafer_layouts import resolve_shape_and_size
             from pygui.backend.wafer.zwafer_parser import ZWaferParser

src/pygui/backend/visualization/wafer_map_item.py

@@ -612,7 +612,6 @@ class WaferMapItem(QQuickPaintedItem):
                 ox = getattr(s, "offset_x", 0.0) * r
                 oy = getattr(s, "offset_y", 0.0) * r
 
-                # Pre-compute metrics using current scaled fonts
                 painter.setFont(id_font)
                 id_fm = painter.fontMetrics()
                 id_line_h = id_fm.height()