fix(napari): show playback FPS label on meta widget (Issue #423)

Author: Tushar7012

movement/napari/loader_widgets.py

@@ -16,6 +16,7 @@
     QFileDialog,
     QFormLayout,
     QHBoxLayout,
+    QLabel,
     QLineEdit,
     QPushButton,
     QWidget,
@@ -440,3 +441,34 @@ def _enable_layer_tooltips():
         """
         settings = get_settings()
         settings.appearance.layer_tooltip_visibility = True
+
+
+class PlaybackFPSWidget(QWidget):
+    """Widget that displays the current napari playback FPS.
+
+    Shows a label that reads the playback FPS directly from napari's
+    application settings (``get_settings().application.playback_fps``) and
+    updates whenever the user changes the playback speed in napari.
+
+    This is intentionally read-only and does *not* measure FPS in real time
+    to avoid flickering or warnings related to private napari attributes.
+    """
+
+    def __init__(self, napari_viewer: Viewer, parent=None):
+        """Initialize the playback FPS widget."""
+        super().__init__(parent=parent)
+        self.viewer = napari_viewer
+        self.setLayout(QFormLayout())
+
+        playback_fps = get_settings().application.playback_fps
+        self.playback_fps_label = QLabel(f"Playback FPS: {playback_fps}")
+        self.playback_fps_label.setObjectName("playback_fps_label")
+        self.layout().addRow(self.playback_fps_label)
+
+        get_settings().application.events.playback_fps.connect(
+            self._on_fps_changed
+        )
+
+    def _on_fps_changed(self, event):
+        """Update the label when the playback fps changes."""
+        self.playback_fps_label.setText(f"Playback FPS: {event.value}")

movement/napari/meta_widget.py

@@ -3,7 +3,7 @@
 from napari.viewer import Viewer
 from qt_niu.collapsible_widget import CollapsibleWidgetContainer
 
-from movement.napari.loader_widgets import DataLoader
+from movement.napari.loader_widgets import DataLoader, PlaybackFPSWidget
 
 
 class MovementMetaWidget(CollapsibleWidgetContainer):
@@ -24,5 +24,12 @@ def __init__(self, napari_viewer: Viewer, parent=None):
             widget_title="Load tracked data",
         )
 
+        # Add the playback fps widget
+        self.add_widget(
+            PlaybackFPSWidget(napari_viewer, parent=self),
+            collapsible=False,
+            widget_title="Playback FPS",
+        )
+
         self.loader = self.collapsible_widgets[0]
         self.loader.expand()  # expand the loader widget by default

tests/test_unit/test_napari_plugin/test_data_loader_widget.py

@@ -26,13 +26,15 @@
 from qtpy.QtWidgets import (
     QComboBox,
     QDoubleSpinBox,
+    QLabel,
     QLineEdit,
     QPushButton,
 )
 
 from movement.napari.loader_widgets import (
     SUPPORTED_BBOXES_FILES,
     DataLoader,
+    PlaybackFPSWidget,
 )
 
 pytestmark = pytest.mark.filterwarnings(
@@ -916,3 +918,39 @@ def test_add_points_and_tracks_layer_style(
         np.testing.assert_allclose(
             bboxes_layer_colormap_sorted, text_colormap_sorted, atol=1e-7
         )
+
+
+# ------------------- tests for PlaybackFPSWidget ----------------------------#
+
+
+def test_playback_fps_widget_instantiation(make_napari_viewer_proxy):
+    """Test that the PlaybackFPSWidget is properly instantiated.
+
+    The label should display the current playback FPS from napari's
+    application settings (``get_settings().application.playback_fps``)
+    and the label widget should be findable by name.
+    """
+    viewer = make_napari_viewer_proxy()
+    widget = PlaybackFPSWidget(viewer)
+
+    label = widget.findChild(QLabel, "playback_fps_label")
+    assert label is not None, "playback_fps_label widget not found."
+    expected_fps = get_settings().application.playback_fps
+    assert label.text() == f"Playback FPS: {expected_fps}"
+
+
+def test_playback_fps_label_updates_on_fps_change(make_napari_viewer_proxy):
+    """Test that the label updates when the playback fps setting changes.
+
+    After the settings event fires, the label text should reflect the
+    new value.
+    """
+    viewer = make_napari_viewer_proxy()
+    widget = PlaybackFPSWidget(viewer)
+
+    new_fps = 42
+    get_settings().application.playback_fps = new_fps
+
+    label = widget.findChild(QLabel, "playback_fps_label")
+    assert label is not None, "playback_fps_label widget not found."
+    assert label.text() == f"Playback FPS: {new_fps}"