adding ContentScaleFactor support to dc - defaulting to 1.0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74282 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dc.h

@@ -521,6 +521,8 @@ public:
 
     // this needs to overidden if the axis is inverted
     virtual void SetAxisOrientation(bool xLeftRight, bool yBottomUp);
+    
+    virtual double GetContentScaleFactor() const { return m_contentScaleFactor; }
 
 #ifdef __WXMSW__
     // Native Windows functions using the underlying HDC don't honour GDI+
@@ -747,6 +749,8 @@ protected:
     double m_scaleX, m_scaleY;  // calculated from logical scale and user scale
 
     int m_signX, m_signY;  // Used by SetAxisOrientation() to invert the axes
+    
+    double m_contentScaleFactor; // used by high resolution displays (retina)
 
     // what is a mm on a screen you don't know the size of?
     double       m_mm_to_pix_x,
@@ -830,6 +834,9 @@ public:
     virtual int GetResolution() const
         { return m_pimpl->GetResolution(); }
 
+    double GetContentScaleFactor() const
+        { return m_pimpl->GetContentScaleFactor(); }
+
     // Right-To-Left (RTL) modes
 
     void SetLayoutDirection(wxLayoutDirection dir)