Made one of the arguments to font::draw_string() not be a reference because

some versions of gcc don't end up doing the right thing when -O3 is supplied.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402520

dlib/gui_widgets/fonts.h

@@ -220,14 +220,14 @@ namespace dlib
     // ------------------------------------------------------------------------------------
 
         template <typename T, typename traits, typename alloc, typename pixel_type>
-        const void draw_string (
+        void draw_string (
             const canvas& c,
             const rectangle& rect,
             const std::basic_string<T,traits,alloc>& str,
             const pixel_type& color,
             typename std::basic_string<T,traits,alloc>::size_type first = 0,
             typename std::basic_string<T,traits,alloc>::size_type last = (std::basic_string<T,traits,alloc>::npos),
-            const rectangle& area_ = rectangle(std::numeric_limits<long>::min(), std::numeric_limits<long>::min(),
+            const rectangle area_ = rectangle(std::numeric_limits<long>::min(), std::numeric_limits<long>::min(),
                                             std::numeric_limits<long>::max(), std::numeric_limits<long>::max())
         ) const
         {
@@ -312,7 +312,7 @@ namespace dlib
             }
         }
         template <typename T, typename traits, typename alloc>
-        const void draw_string (
+        void draw_string (
             const canvas& c,
             const rectangle& rect,
             const std::basic_string<T,traits,alloc>& str

dlib/gui_widgets/fonts_abstract.h

@@ -276,14 +276,14 @@ namespace dlib
         !*/
 
         template <typename T, typename traits, typename alloc, typename pixel_type>
-        const void draw_string (
+        void draw_string (
             const canvas& c,
             const rectangle& rect,
             const std::basic_string<T,traits,alloc>& str,
             const pixel_type& color = rgb_pixel(0,0,0),
             typename std::basic_string<T,traits,alloc>::size_type first = 0,
             typename std::basic_string<T,traits,alloc>::size_type last = std::basic_string<T,traits,alloc>::npos,
-            const rectangle& area = rectangle(-infinity,-infinity,infinity,infinity)
+            const rectangle area = rectangle(-infinity,-infinity,infinity,infinity)
         ) const;
         /*!
             requires