Consider scale factor changes to OSR browsers when switching monitors (issue #1774)

libcef/browser/osr/render_widget_host_view_osr.cc

@@ -1345,7 +1345,10 @@ void CefRenderWidgetHostViewOSR::SetDeviceScaleFactor() {
 
 void CefRenderWidgetHostViewOSR::ResizeRootLayer() {
   SetFrameRate();
+
+  const float orgScaleFactor = scale_factor_;
   SetDeviceScaleFactor();
+  const bool scaleFactorDidChange = (orgScaleFactor != scale_factor_);
 
   gfx::Size size;
   if (!IsPopupWidget())
@@ -1353,7 +1356,7 @@ void CefRenderWidgetHostViewOSR::ResizeRootLayer() {
   else
     size = popup_position_.size();
 
-  if (size == root_layer_->bounds().size())
+  if (!scaleFactorDidChange && size == root_layer_->bounds().size())
     return;
 
   const gfx::Size& size_in_pixels =

tests/cefclient/browser/browser_window_osr_mac.mm

@@ -1099,6 +1099,19 @@ BrowserOpenGLView* GLView(NSView* view) {
   return device_scale_factor_;
 }
 
+- (void)viewDidChangeBackingProperties {
+  const CGFloat device_scale_factor = [self getDeviceScaleFactor];
+
+  if (device_scale_factor == device_scale_factor_)
+    return;
+
+  CefRefPtr<CefBrowser> browser = [self getBrowser];
+  if (browser) {
+    browser->GetHost()->NotifyScreenInfoChanged();
+    browser->GetHost()->WasResized();
+  }
+}
+
 - (bool)isOverPopupWidgetX:(int)x andY:(int)y {
   CefRect rc = renderer_->popup_rect();
   int popup_right = rc.x + rc.width;