made ProvideBackground() const

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@17329 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/panelg.h

@@ -83,7 +83,7 @@ public:
 
 #ifdef __WXUNIVERSAL__
     virtual bool IsCanvasWindow() const { return TRUE; }
-    virtual bool ProvidesBackground() { return TRUE; }
+    virtual bool ProvidesBackground() const { return TRUE; }
 #endif
 
     WX_DECLARE_CONTROL_CONTAINER();

include/wx/univ/toplevel.h

@@ -143,7 +143,7 @@ public:
     virtual int GetMinWidth() const;
     virtual int GetMinHeight() const;
 
-    virtual bool ProvidesBackground() { return TRUE; }
+    virtual bool ProvidesBackground() const { return TRUE; }
     
 protected:
     // handle titlebar button click event

include/wx/univ/window.h

@@ -179,7 +179,7 @@ public:
     // to be used with function above: transparent windows get
     // their background from parents that return TRUE here,
     // so this is mostly for wxPanel, wxTopLevelWindow etc.
-    virtual bool ProvidesBackground() { return FALSE; }
+    virtual bool ProvidesBackground() const { return FALSE; }
 
     // return TRUE if this control can be highlighted when the mouse is over
     // it (the theme decides itself whether it is really highlighted or not)