applets: workaround for Qt window embedding initial size bug

artiq/applets/simple.py

@@ -36,6 +36,9 @@ class AppletIPCClient(AsyncioChildComm):
                          action)
             self.close_cb()
 
+    def fix_initial_size(self):
+        self.write_pyon({"action": "fix_initial_size"})
+
     async def listen(self):
         data = None
         while True:
@@ -133,13 +136,15 @@ class SimpleApplet:
         # 2. applet creates native window without showing it, and get its ID
         # 3. applet sends the ID to host, host embeds the widget
         # 4. applet shows the widget
-        # Doing embedding the other way around (using QWindow.setParent in the
-        # applet) breaks resizing.
+        # 5. parent resizes the widget
         if self.args.embed is not None:
             self.ipc.set_close_cb(self.main_widget.close)
             win_id = int(self.main_widget.winId())
             self.loop.run_until_complete(self.ipc.embed(win_id))
             self.main_widget.show()
+            self.ipc.fix_initial_size()
+        else:
+            self.main_widget.show()
 
     def sub_init(self, data):
         self.data = data

artiq/gui/applets.py

@@ -44,7 +44,7 @@ class AppletIPCServer(AsyncioParentComm):
                     return
         self.write_pyon({"action": "mod", "mod": mod})
 
-    async def serve(self, embed_cb):
+    async def serve(self, embed_cb, fix_initial_size_cb):
         self.datasets_sub.notify_cbs.append(self._on_mod)
         try:
             while True:
@@ -54,6 +54,8 @@ class AppletIPCServer(AsyncioParentComm):
                     if action == "embed":
                         embed_cb(obj["win_id"])
                         self.write_pyon({"action": "embed_done"})
+                    elif action == "fix_initial_size":
+                        fix_initial_size_cb()
                     elif action == "subscribe":
                         self.datasets = obj["datasets"]
                         if self.datasets_sub.model is not None:
@@ -74,8 +76,9 @@ class AppletIPCServer(AsyncioParentComm):
         finally:
             self.datasets_sub.notify_cbs.remove(self._on_mod)
 
-    def start(self, embed_cb):
-        self.server_task = asyncio.ensure_future(self.serve(embed_cb))
+    def start(self, embed_cb, fix_initial_size_cb):
+        self.server_task = asyncio.ensure_future(
+            self.serve(embed_cb, fix_initial_size_cb))
 
     async def stop(self):
         self.server_task.cancel()
@@ -109,14 +112,20 @@ class AppletDock(dockarea.Dock):
         except:
             logger.warning("Applet %s failed to start", self.applet_name,
                            exc_info=True)
-        self.ipc.start(self.embed)
+        self.ipc.start(self.embed, self.fix_initial_size)
 
     def embed(self, win_id):
         logger.debug("capturing window 0x%x for %s", win_id, self.applet_name)
-        embed_window = QtGui.QWindow.fromWinId(win_id)
-        self.embed_widget = QtWidgets.QWidget.createWindowContainer(embed_window)
+        self.embed_window = QtGui.QWindow.fromWinId(win_id)
+        self.embed_widget = QtWidgets.QWidget.createWindowContainer(
+            self.embed_window)
         self.addWidget(self.embed_widget)
 
+    # HACK: This function would not be needed if Qt window embedding
+    # worked correctly.
+    def fix_initial_size(self):
+        self.embed_window.resize(self.embed_widget.size())
+
     async def terminate(self):
         if hasattr(self, "ipc"):
             await self.ipc.stop()