Implement wxWindow::GetDPI() on macOS and iOS

include/wx/osx/window.h

@@ -120,6 +120,8 @@ public:
     virtual bool UnregisterHotKey(int hotkeyId) wxOVERRIDE;
 #endif // wxUSE_HOTKEY
 
+    virtual wxSize GetDPI() const wxOVERRIDE;
+
 #if wxUSE_DRAG_AND_DROP
     virtual void SetDropTarget( wxDropTarget *dropTarget ) wxOVERRIDE;
 

src/osx/window_osx.cpp

@@ -2599,6 +2599,19 @@ bool wxWindowMac::OSXHandleKeyEvent( wxKeyEvent& event )
     return handled ;
 }
 
+wxSize wxWindowMac::GetDPI() const
+{
+    wxNonOwnedWindow* tlw = MacGetTopLevelWindow() ;
+
+    double scaleFactor;
+    if ( tlw )
+        scaleFactor = tlw->GetContentScaleFactor();
+    else
+        scaleFactor = wxOSXGetMainScreenContentScaleFactor();
+
+    return wxSize(wxRound(scaleFactor*72.0),wxRound(scaleFactor*72.0));
+}
+
 //
 // wxWidgetImpl
 //