GSoC: Integrate new CommonSalLayout in unx/ code

Change-Id: I991cb5cbd2adad4f4c9f62f807990b9fde2a5133

vcl/README.vars

@@ -6,6 +6,7 @@ SAL_USE_VCLPLUGIN - use a VCL plugin
 SAL_NO_NWF - disable native widgets
 SAL_FORCEDPI - force a specific DPI (gtk & gtk3 plugins only)
 SAL_FORCE_HC - force high-contrast mode
+SAL_USE_COMMON_LAYOUT - use CommonSalLayout layout engine for text layout
 
 VCL_DOUBLEBUFFERING_AVOID_PAINT - don't paint the buffer, useful to see where we do direct painting
 VCL_DOUBLEBUFFERING_FORCE_ENABLE - enable double buffered painting

vcl/unx/generic/gdi/cairotextrender.cxx

@@ -42,6 +42,7 @@
 
 #include <cairo.h>
 #include <cairo-ft.h>
+#include "CommonSalLayout.hxx"
 
 namespace {
 
@@ -540,7 +541,10 @@ SalLayout* CairoTextRender::GetTextLayout( ImplLayoutArgs& rArgs, int nFallbackL
         }
         else
 #endif
-            pLayout = new ServerFontLayout( *mpServerFont[ nFallbackLevel ] );
+            if (getenv("SAL_USE_COMMON_LAYOUT"))
+                pLayout = new CommonSalLayout(*mpServerFont[nFallbackLevel]);
+            else
+                pLayout = new ServerFontLayout(*mpServerFont[nFallbackLevel]);
     }
 
     return pLayout;