feat: restructure overlay and video widget integration for improved rendering

app/ui/main_window.py

@@ -6,7 +6,7 @@ import logging
 
 from PySide6.QtCore import Qt, QTimer
 from PySide6.QtMultimediaWidgets import QVideoWidget
-from PySide6.QtWidgets import QLabel, QMainWindow, QSizePolicy, QStatusBar
+from PySide6.QtWidgets import QLabel, QMainWindow, QSizePolicy, QStatusBar, QVBoxLayout, QWidget
 
 from app.camera.camera_enumerator import CameraEnumerator, CameraInfo
 from app.camera.camera_service import CameraService
@@ -41,21 +41,34 @@ class MainWindow(QMainWindow):
         self._dispatcher = FrameDispatcher(self)
         self._telemetry = TelemetryCollector(parent=self)
 
-        # --- Video widget (central widget) ---
-        self._video_widget = QVideoWidget(self)
+        # --- Central container ---
+        # We need an extra QWidget layer between QMainWindow and QVideoWidget so
+        # that OverlayWidget can be a sibling of QVideoWidget (not its child).
+        # QVideoWidget renders via a native D3D/GL surface that occludes any
+        # QWidget children painted on top of it.
+        self._container = QWidget(self)
+        self._container.setStyleSheet("background: black;")
+        container_layout = QVBoxLayout(self._container)
+        container_layout.setContentsMargins(0, 0, 0, 0)
+        container_layout.setSpacing(0)
+
+        # --- Video widget ---
+        self._video_widget = QVideoWidget(self._container)
         self._video_widget.setSizePolicy(
             QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding
         )
         self._video_widget.setAspectRatioMode(Qt.AspectRatioMode.KeepAspectRatio)
-        self.setCentralWidget(self._video_widget)
+        container_layout.addWidget(self._video_widget)
+        self.setCentralWidget(self._container)
 
         # Connect camera session to video widget — this is the zero-copy render path
         self._camera_service.capture_session().setVideoOutput(self._video_widget)
 
         # --- Overlay ---
-        self._overlay = OverlayWidget(parent=self._video_widget)
+        # Sibling of QVideoWidget inside _container; positioned manually so it
+        # floats above the video without being occluded by the native GL surface.
+        self._overlay = OverlayWidget(parent=self._container)
         self._overlay.raise_()
-        self._overlay.resize(self._video_widget.size())
 
         # --- Menu bar ---
         self._menu = AppMenuBar(self)
@@ -72,6 +85,8 @@ class MainWindow(QMainWindow):
 
         # --- Enumerate cameras and start ---
         QTimer.singleShot(0, self._initialise_cameras)
+        # Reposition overlay after the event loop starts (layout is finalised)
+        QTimer.singleShot(0, self._reposition_overlay)
 
     # ------------------------------------------------------------------
     # Initialisation
@@ -161,9 +176,16 @@ class MainWindow(QMainWindow):
 
     def resizeEvent(self, event) -> None:  # noqa: N802
         super().resizeEvent(event)
-        # Keep overlay covering the video widget
-        if hasattr(self, "_overlay") and hasattr(self, "_video_widget"):
-            self._overlay.resize(self._video_widget.size())
+        self._reposition_overlay()
+
+    def _reposition_overlay(self) -> None:
+        """Keep the overlay covering the video widget exactly."""
+        if not (hasattr(self, "_overlay") and hasattr(self, "_video_widget")):
+            return
+        # _overlay and _video_widget share the same parent (_container),
+        # so video_widget.geometry() is already in the right coordinate space.
+        self._overlay.setGeometry(self._video_widget.geometry())
+        self._overlay.raise_()
 
     def closeEvent(self, event) -> None:  # noqa: N802
         self._camera_service.stop()