Play/Render: ensure no running ovgen before asking for output path

ovgenpy/gui/__init__.py

@@ -118,26 +118,39 @@ class MainWindow(qw.QMainWindow):
 
     def on_action_play(self):
         """ Launch ovgen and ffplay. """
-        outputs = [FFplayOutputConfig()]
         error_msg = 'Cannot play, another play/render is active'
-        self.play_thread(outputs, None, error_msg)
+        with self.ovgen_thread as t:
+            if t is not None:
+                self.ovgen_thread.unlock()
+                qw.QMessageBox.critical(self, 'Error', error_msg)
+                return
+
+            outputs = [FFplayOutputConfig()]
+            self.play_thread(outputs, dlg=None)
 
     def on_action_render(self):
         """ Get file name. Then show a progress dialog while rendering to file. """
-        video_path = os.path.join(self.cfg_dir, self.file_stem) + cli.VIDEO_NAME
+        error_msg = 'Cannot render to file, another play/render is active'
+        with self.ovgen_thread as t:
+            if t is not None:
+                self.ovgen_thread.unlock()
+                qw.QMessageBox.critical(self, 'Error', error_msg)
+                return
 
+            video_path = os.path.join(self.cfg_dir, self.file_stem) + cli.VIDEO_NAME
             name, file_type = qw.QFileDialog.getSaveFileName(
                 self, "Render to Video", video_path, "MP4 files (*.mp4);;All files (*)"
             )
             if name != '':
                 # FIXME what if missing mp4?
                 dlg = OvgenProgressDialog(self, 'Rendering video')
+
                 outputs = [FFmpegOutputConfig(name)]
-            error_msg = 'Cannot render to file, another play/render is active'
+                self.play_thread(outputs, dlg)
-            self.play_thread(outputs, dlg, error_msg)
 
     def play_thread(self, outputs: List[IOutputConfig],
-                    dlg: Optional['OvgenProgressDialog'], error_msg: str):
+                    dlg: Optional['OvgenProgressDialog']):
+        """ self.ovgen_thread MUST be locked. """
         arg = self._get_args(outputs)
         if dlg:
             arg = attr.evolve(arg,
@@ -146,16 +159,8 @@ class MainWindow(qw.QMainWindow):
                 is_aborted=dlg.wasCanceled,
                 on_end=dlg.reset,   # TODO dlg.close
             )
-        with self.ovgen_thread as t:
-            if t is not None:
-                self.ovgen_thread.unlock()
-                if dlg:
-                    dlg.close()
-                qw.QMessageBox.critical(self, 'Error', error_msg)
-                return
 
         cfg = copy_config(self.model.cfg)
-
         t = self.ovgen_thread.obj = OvgenThread(self, cfg, arg)
         # Assigns self.ovgen_thread.set(None) when finished.
         t.start()