Do nothing in wxMemoryDC::SelectObject() if the bitmap is already selected.

It doesn't make sense to make a copy of the bitmap in order to select it into
wxMemoryDC if it's already selected into it.

See #11640.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65913 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/dcbase.cpp

@@ -236,6 +236,12 @@ wxMemoryDC::wxMemoryDC(wxDC *dc)
 
 void wxMemoryDC::SelectObject(wxBitmap& bmp)
 {
+    if ( bmp.IsSameAs(GetSelectedBitmap()) )
+    {
+        // Nothing to do, this bitmap is already selected.
+        return;
+    }
+
     // make sure that the given wxBitmap is not sharing its data with other
     // wxBitmap instances as its contents will be modified by any drawing
     // operation done on this DC