Fixed the crash on termination of main window due to cv2 camera stream not closed properly

Author: gnthibault

Dashboard/CameraWidget.py

@@ -11,13 +11,20 @@ class Thread(QThread):
     changePixmap = pyqtSignal(QImage)
 
     def __init__(self, parent=None, url=0):
-      super(QThread, self).__init__(parent)
-      self.url = url
+        super(QThread, self).__init__(parent)
+        self.url = url
+        self.is_running = True
+        self.cap = None
+
+    def stop(self):
+        if self.cap is not None:
+            self.cap.release()
+        self.is_running = False
 
     def run(self):
-        cap = cv2.VideoCapture(self.url)
-        while True:
-            ret, frame = cap.read()
+        self.cap = cv2.VideoCapture(self.url)
+        while self.is_running:
+            ret, frame = self.cap.read()
             if ret:
                 rgbImage = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
                 convertToQtFormat = QImage(rgbImage.data,
@@ -27,7 +34,15 @@ def run(self):
                 p = convertToQtFormat.scaled(640, 480, Qt.KeepAspectRatio)
                 self.changePixmap.emit(p)
 
+            if self.isInterruptionRequested():
+                self.stop()
+
 class CameraWidget(QFrame):
+    """
+        From the documentation: The QFrame class is the base class of widgets
+        that can have a frame.
+
+    """
     def __init__(self, parent=None, url='rtsp://192.168.1.64/1'):
         super().__init__()
         self.url=url
@@ -37,6 +52,10 @@ def __init__(self, parent=None, url='rtsp://192.168.1.64/1'):
     def setImage(self, image):
         self.label.setPixmap(QPixmap.fromImage(image))
 
+    def close(self):
+        self.thread.requestInterruption()
+        self.thread.wait()
+
     def init_UI(self):
         #self.setWindowTitle(self.title)
         #self.setGeometry(self.left, self.top, self.width, self.height)
@@ -52,6 +71,6 @@ def init_UI(self):
         self.setLayout(layout)
 
         # Start acquisition thread
-        th = Thread(self, self.url)
-        th.changePixmap.connect(self.setImage)
-        th.start()
+        self.thread = Thread(self, self.url)
+        self.thread.changePixmap.connect(self.setImage)
+        self.thread.start()

apps/launch_qt_dashboard.py

@@ -14,7 +14,7 @@
 from PyQt5.QtWidgets import QWidget, QSizePolicy, QVBoxLayout, QMessageBox
 from PyQt5.QtGui import QVector3D
 from PyQt5.Qt3DExtras import Qt3DWindow, QOrbitCameraController
-from PyQt5.QtCore import Qt, QThread, pyqtSlot
+from PyQt5.QtCore import Qt, QThread, pyqtSignal, pyqtSlot
 
 # Astropy stuff
 from astropy import units as u
@@ -43,12 +43,16 @@
 
 
 class MainWindow(QMainWindow):
-    def __init__(self, view3D, camera_widget=None, dashboard_widget=None):
+
+    closing = pyqtSignal()
+ 
+    def __init__(self, view3D=None, camera_widget=None, dashboard_widget=None):
         super().__init__()
 
         # Various views/widgets
         self.view3D = view3D
         self.camera_widget = camera_widget
+        self.closing.connect(self.camera_widget.close)
         self.dashboard_widget = dashboard_widget
 
         # Change visual parameters and setup widgets on the main window
@@ -79,39 +83,43 @@ def init_UI(self):
         self.helpMenu.addAction(self.creditsAct)
 
         # General layout
-        self.layout = QVBoxLayout()
-
-        # 3D view
-        #self.dock_view3D = QDockWidget('Mount simulator', self)
-        #self.addDockWidget(Qt.BottomDockWidgetArea, self.dock_view3D)
-        self.widget3D = QWidget.createWindowContainer(self.view3D.window, self)
-        #self.widget3D.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed)
-        #self.dock_view3D.setWidget(self.widget3D)
-        self.setCentralWidget(self.widget3D)
-        #self.layout.addWidget(self.widget3D)
-
-        # Dock safety camera on the right
+        #self.layout = QVBoxLayout()
+
+        # Webbrowser for dashboard should be the main widget
+        if self.dashboard_widget is not None:
+            #self.dock_dashboard = QDockWidget('Main dashboard', self)
+            #self.addDockWidget(Qt.RightDockWidgetArea, self.dock_dashboard)
+            #self.dashboard_widget.setSizePolicy(QSizePolicy.Fixed,
+            #                                    QSizePolicy.Fixed)
+            #self.dock_dashboard.setWidget(self.dashboard_widget)
+            self.setCentralWidget(self.dashboard_widget)
+
+        # Dock safety camera on the Left
         if self.camera_widget is not None:
             self.dock_camera = QDockWidget('Surveillance camera', self)
             self.addDockWidget(Qt.LeftDockWidgetArea, self.dock_camera)
             #self.camera_widget.setSizePolicy(QSizePolicy.Fixed,
             #                                 QSizePolicy.Fixed)
             self.dock_camera.setWidget(self.camera_widget)
 
-        # Dock webbrowser for dashboard on the right
-        if self.dashboard_widget is not None:
-            self.dock_dashboard = QDockWidget('Main dashboard', self)
-            self.addDockWidget(Qt.RightDockWidgetArea, self.dock_dashboard)
-            #self.dashboard_widget.setSizePolicy(QSizePolicy.Fixed,
-            #                                    QSizePolicy.Fixed)
-            self.dock_dashboard.setWidget(self.dashboard_widget)        
+        # 3D view set as right widget
+        if self.view3D is not None:
+            self.widget3D = QWidget.createWindowContainer(self.view3D.window, self)
+            self.dock_view3D = QDockWidget('Mount simulator', self)
+            self.addDockWidget(Qt.RightDockWidgetArea, self.dock_view3D)
+            #self.widget3D.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed)
+            self.dock_view3D.setWidget(self.widget3D)
+            #self.setCentralWidget(self.widget3D)
+            #self.layout.addWidget(self.widget3D)
 
         # Global stuff
-        self.setLayout(self.layout)
+        #self.setLayout(self.layout)
         self.setWindowTitle('Remote observatory dashboard')
         self.show()
 
     def closeEvent(self, event):
+        # emit a signal for registered custom slot to perform cleanup if needed
+        self.closing.emit()
         self.quit()
 
     def quit(self):
@@ -173,6 +181,14 @@ def update_coord(self, coord):
 
 if __name__ == "__main__":
 
+    def trap_exc_during_debug(*args):
+        # when app raises uncaught exception, print info
+        print(args)
+
+    # install exception hook: without this, uncaught exception would cause
+    # application to exit
+    sys.excepthook = trap_exc_during_debug
+
     # load the logging configuration
     logging.config.fileConfig('logging.ini')