Update GAL observers for all frames, not just calling frame.

Also don't rely on UpdateScaleFactor to do it as it only does it
if the scale factor changed.

Fixes https://gitlab.com/kicad/code/kicad/issues/5621

common/gal/gal_display_options.cpp

@@ -100,9 +100,9 @@ void GAL_DISPLAY_OPTIONS::ReadCommonConfig( COMMON_SETTINGS& aSettings, wxWindow
             aSettings.m_Graphics.cairo_aa_mode );
 
     m_dpi = DPI_SCALING( &aSettings, aWindow );
-
-    // Also calls NotifyChanged
     UpdateScaleFactor();
+
+    NotifyChanged();
 }
 
 

common/widgets/gal_options_panel.cpp

@@ -222,7 +222,5 @@ bool GAL_OPTIONS_PANEL::TransferDataFromWindow()
 
     m_galOptions.m_forceDisplayCursor = m_forceCursorDisplay->GetValue();
 
-    m_galOptions.NotifyChanged();
-
     return true;
 }