Adding "experimental_timeline" debug preference, to allow for conditi…

…onal testing of a non-webview timeline widget. For now though, it's a blank QWidget.

src/settings/_default.settings

@@ -378,6 +378,14 @@
     "category": "Debug",
     "setting": "send_metrics"
   },
+  {
+    "value": false,
+    "title": "Use Experimental Timeline (not recommended)",
+    "type": "bool",
+    "category": "Debug",
+    "setting": "experimental_timeline",
+    "restart": true
+  },
   {
     "value": true,
     "title": "Show Export Dialog when Finished",

src/windows/main_window.py

@@ -1020,7 +1020,8 @@ def actionPreview_File_trigger(self, checked=True):
     def movePlayhead(self, position_frames):
         """Update playhead position"""
         # Notify preview thread
-        self.timeline.movePlayhead(position_frames)
+        if hasattr(self.timeline, 'movePlayhead'):
+            self.timeline.movePlayhead(position_frames)
 
     def SetPlayheadFollow(self, enable_follow):
         """ Enable / Disable follow mode """
@@ -3248,7 +3249,10 @@ def __init__(self, *args):
         self.timeline_sync = TimelineSync(self)
 
         # Setup timeline
-        self.timeline = TimelineWebView(self)
+        if s.get("experimental_timeline"):
+            self.timeline = QWidget(self)
+        else:
+            self.timeline = TimelineWebView(self)
         self.frameWeb.layout().addWidget(self.timeline)
 
         # Configure the side docks to full-height