Add support for custom attributes to wxGTK wxDataViewCustomRenderer.

Call SetAttr() to store them in wxDataViewCustomRenderer before rendering it
and also honour the attributes in RenderText() (by reusing the same code we
already use for wxDataViewTextRenderer).

The attributes now work correctly in dataview sample under wxGTK as well.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62596 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dvrenderers.h

@@ -13,6 +13,7 @@
 #define _WX_GTK_DVRENDERERS_H_
 
 typedef struct _GdkRectangle GdkRectangle;
+typedef struct _GtkCellRendererText GtkCellRendererText;
 
 // ---------------------------------------------------------
 // wxDataViewTextRenderer
@@ -44,6 +45,7 @@ public:
     virtual void SetAlignment( int align );
 
     virtual bool GtkSupportsAttrs() const { return true; }
+    virtual bool GtkSetAttr(const wxDataViewItemAttr& attr);
 
 protected:
     // implementation of Set/GetValue()
@@ -128,13 +130,23 @@ public:
         m_renderParams.flags = flags;
     }
 
+    // we may or not support attributes, as we don't know it, return true to
+    // make it possible to use them
+    virtual bool GtkSupportsAttrs() const { return true; }
+
+    virtual bool GtkSetAttr(const wxDataViewItemAttr& attr)
+    {
+        SetAttr(attr);
+        return !attr.IsDefault();
+    }
+
 protected:
     bool Init(wxDataViewCellMode mode, int align);
 
 private:
     wxDC        *m_dc;
 
-    GtkCellRenderer      *m_text_renderer;
+    GtkCellRendererText      *m_text_renderer;
 
     // parameters of the original render() call stored so that we could pass
     // them forward to m_text_renderer if our RenderText() is called