Make wxGTK's wxScrolledWindow set m_x/xScrollLines to 0

if scrollbars disappear (instead of 1) as per wxMSW.
  Expose m_x/yScrollLines in public getters.
  Correct window origin for scrolled window in RTL.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41186 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/scrolwin.h

@@ -68,6 +68,10 @@ public:
     int GetScrollPageSize(int orient) const;
     void SetScrollPageSize(int orient, int pageSize);
 
+    // get the number of lines the window can scroll, 
+    // returns 0 if no scrollbars are there.
+    int GetScrollLines( int orient ) const;
+
     // Set the x, y scrolling increments.
     void SetScrollRate( int xstep, int ystep );