Experimental screen scaling code, to adjust QT_SCALE_FACTOR env var a…

…utomatically when changing screen DPI. This can be disabled in the "adjust_scaling_factor" settings file.

src/settings/_default.settings

@@ -25,6 +25,13 @@
     "category": "General",
     "setting": "unique_install_id"
   },
+  {
+    "value": true,
+    "title": "",
+    "type": "hidden",
+    "category": "General",
+    "setting": "adjust_scaling_factor"
+  },
   {
     "value": "smileys-emotion",
     "title": "",

src/windows/main_window.py

@@ -3167,6 +3167,22 @@ def eventFilter(self, obj, event):
                 event.accept()
         return super(MainWindow, self).eventFilter(obj, event)
 
+    def adjust_scaling(self):
+        """Adjust scaling factor for new screen. This is primarily to adjust our
+        scaling factor to match the OS display scaling on the primary screen where
+        OpenShot is displayed."""
+        screen = get_app().primaryScreen()
+        logical_dpi = screen.logicalDotsPerInch()
+        physical_dpi = screen.physicalDotsPerInch()
+        scale_factor = logical_dpi / physical_dpi
+        os.environ['QT_SCALE_FACTOR'] = str(scale_factor)
+        log.info(f"Adjusted QT_SCALE_FACTOR factor dynamically to: {scale_factor}")
+
+    def on_screen_changed(self, new_screen):
+        """Listen for screen changes"""
+        log.info(f"Detected screen change: {new_screen}")
+        self.adjust_scaling()
+
     def __init__(self, *args):
 
         # Create main window base class
@@ -3451,6 +3467,14 @@ def __init__(self, *args):
         # Save settings
         s.save()
 
+        # Listen for screen changes (i.e. High DPI to Low DPI screen)
+        if s.get("adjust_scaling_factor"):
+            log.info("Listen to screen display scaling changes...")
+            for screen in app.screens():
+                screen.logicalDotsPerInchChanged.connect(self.on_screen_changed)
+        else:
+            log.info("Ignore screen display scaling changes...")
+
         # Refresh frame
         QTimer.singleShot(100, self.refreshFrameSignal.emit)