Draft implementation of Fusion heartbeat/pulse so UI closes after Fusion is closed

openpype/hosts/fusion/api/menu.py

@@ -15,6 +15,8 @@ from openpype.hosts.fusion.api import (
     set_framerange
 )
 
+from .pulse import FusionPulse
+
 
 class Spacer(QtWidgets.QWidget):
     def __init__(self, height, *args, **kwargs):
@@ -121,6 +123,10 @@ class OpenPypeMenu(QtWidgets.QWidget):
         self.register_callback("taskChanged", self.on_task_changed)
         self.on_task_changed()
 
+        # Force close current process if Fusion is closed
+        self._pulse = FusionPulse(parent=self)
+        self._pulse.start()
+
     def on_task_changed(self):
         # Update current context label
         label = api.Session["AVALON_ASSET"]

openpype/hosts/fusion/api/pulse.py

@@ -0,0 +1,62 @@
+import os
+import sys
+
+from Qt import QtCore, QtWidgets
+
+
+class PulseThread(QtCore.QThread):
+    no_response = QtCore.Signal()
+
+    def __init__(self, parent=None):
+        super(PulseThread, self).__init__(parent=parent)
+
+        # Interval in milliseconds
+        self._interval = os.environ.get("OPENPYPE_FUSION_PULSE_INTERVAL", 1000)
+
+    def run(self):
+        app = getattr(sys.modules["__main__"], "app", None)
+
+        while True:
+            if self.isInterruptionRequested():
+                return
+            try:
+                app.Test()
+            except Exception:
+                self.no_response.emit()
+
+            self.msleep(self._interval)
+
+
+class FusionPulse(QtCore.QObject):
+    """A Timer that checks whether host app is still alive.
+
+    This checks whether the Fusion process is still active at a certain
+    interval. This is useful due to how Fusion runs its scripts. Each script
+    runs in its own environment and process (a `fusionscript` process each).
+    If Fusion would go down and we have a UI process running at the same time
+    then it can happen that the `fusionscript.exe` will remain running in the
+    background in limbo due to e.g. a Qt interface's QApplication that keeps
+    running infinitely.
+
+    Warning:
+        When the host is not detected this will automatically exit
+        the current process.
+
+    """
+
+    def __init__(self, parent=None):
+        super(FusionPulse, self).__init__(parent=parent)
+        self._thread = PulseThread(parent=self)
+        self._thread.no_response.connect(self.on_no_response)
+
+    def on_no_response(self):
+        print("Pulse detected no response from Fusion..")
+        sys.exit(1)
+
+    def start(self):
+        self._thread.start()
+
+    def stop(self):
+        self._thread.requestInterruption()
+
+