make x11 dc could get cairo context, so the graphic module could use in x11. This use cairo xlib backend.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77853 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/x11/dcclient.h

@@ -108,6 +108,8 @@ public:
 
     virtual void ComputeScaleAndOrigin();
 
+    virtual void* GetCairoContext() const wxOVERRIDE;
+
 protected:
     // implementation
     // --------------

src/generic/graphicc.cpp

@@ -1744,6 +1744,12 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, const wxWindowDC&
 #endif
 #endif
 
+#ifdef __WXX11__
+    cairo_t* cr = static_cast<cairo_t*>(dc.GetImpl()->GetCairoContext());
+    if ( cr )
+        Init(cairo_reference(cr));
+#endif
+
 #ifdef __WXMAC__
     CGContextRef cgcontext = (CGContextRef)dc.GetWindow()->MacGetCGContextRef();
     cairo_surface_t* surface = cairo_quartz_surface_create_for_cg_context(cgcontext, width, height);

src/x11/dcclient.cpp

@@ -28,6 +28,8 @@
 #include "wx/x11/dcclient.h"
 #include "wx/x11/dcmemory.h"
 
+#include "cairo-xlib.h"
+
 #if wxUSE_UNICODE
 #include "glib.h"
 #include "pango/pangoxft.h"
@@ -343,6 +345,17 @@ void wxWindowDCImpl::SetUpDC()
     }
 }
 
+void* wxWindowDCImpl::GetCairoContext() const
+{
+    int width, height;
+    DoGetSize(&width, &height);
+    cairo_surface_t *surface;
+    surface = cairo_xlib_surface_create((Display*) m_display, (Drawable) m_x11window,
+                    DefaultVisual((Display*) m_display, 0), width, height);
+    cairo_t *cr = cairo_create(surface);
+    return cr;
+}
+
 void wxWindowDCImpl::DoGetSize( int* width, int* height ) const
 {
     wxCHECK_RET( m_window, wxT("GetSize() doesn't work without window") );