view: add :will_add_event vfunc and stub methods

Note: this commit probably won't build, but this is the right order of
keeping history.

src/gcal-view.h

@@ -20,10 +20,7 @@
 #ifndef __GCAL_VIEW_H__
 #define __GCAL_VIEW_H__
 
-#include <glib-object.h>
-#include <gtk/gtk.h>
-
-#include <libical/icaltime.h>
+#include "gcal-event-widget.h"
 
 G_BEGIN_DECLS
 
@@ -73,6 +70,9 @@ struct _GcalViewIface
   gboolean        (*draw_event)                         (GcalView *view, icaltimetype *start_date, icaltimetype *end_date);
   GtkWidget*      (*get_by_uuid)                        (GcalView *view, const gchar *uuid);
   void            (*clear)                              (GcalView *view);
+
+  /* Newer API */
+  gboolean        (*will_add_event)                     (GcalView *view, GcalEventWidget *event);
 };
 
 GType         gcal_view_get_type                      (void);
@@ -113,6 +113,9 @@ GtkWidget*    gcal_view_get_by_uuid                   (GcalView     *view,
 
 void          gcal_view_clear                         (GcalView     *view);
 
+gboolean      gcal_view_will_add_event                (GcalView     *view,
+						       GcalEventWidget *event);
+
 G_END_DECLS
 
 #endif /* __GCAL_MONTH_VIEW_H__ */