Implement wxComboCtrl::GetSizeFromTextSize().

Improve calculation of wxComboCtrl best size which doesn't work correctly for
non-default fonts as shown by r72935. It is still not perfect but better now.

Closes #14825.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/combo.h

@@ -541,7 +541,10 @@ protected:
     void DestroyPopup();
 
     // override the base class virtuals involved in geometry calculations
+    // The common version only sets a default width, so the derived classes
+    // should override it and set the height and change the width as needed.
     virtual wxSize DoGetBestSize() const;
+    virtual wxSize DoGetSizeFromTextSize(int xlen, int ylen = -1) const;
 
     // also set the embedded wxTextCtrl colours
     virtual bool SetForegroundColour(const wxColour& colour);