[gtksourceview] Add more docs about using icons in the completion

[Paolo Borelli <pborelli src gnome org>]

commit 4bea03e762ccd7529ab1e874ff23fa87786b19d5
Author: Paolo Borelli <pborelli gnome org>
Date:   Sat Aug 15 12:34:43 2015 +0200

    Add more docs about using icons in the completion

 gtksourceview/gtksourcecompletionproposal.c |    9 +++++++++
 gtksourceview/gtksourcecompletionprovider.c |    6 ++++++
 2 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/gtksourceview/gtksourcecompletionproposal.c b/gtksourceview/gtksourcecompletionproposal.c
index 8e063a3..2aeecb2 100644
--- a/gtksourceview/gtksourcecompletionproposal.c
+++ b/gtksourceview/gtksourcecompletionproposal.c
@@ -28,6 +28,15 @@
  * The proposal interface represents a completion item in the completion window.
  * It provides information on how to display the completion item and what action
  * should be taken when the completion item is activated.
+ *
+ * The proposal is displayed in the completion window with a label and
+ * optionally an icon.
+ * The label may be specified using plain text or markup by implementing
+ * the corresponding get function. Only one of those get functions
+ * should return a value different from %NULL.
+ * The icon may be specified as a #GdkPixbuf, as an icon name or as a #GIcon by
+ * implementing the corresponding get function. Only one of those get functions
+ * should return a value different from %NULL.
  */
 
 #include "gtksourcecompletionproposal.h"
diff --git a/gtksourceview/gtksourcecompletionprovider.c b/gtksourceview/gtksourcecompletionprovider.c
index 1b3ad81..248599d 100644
--- a/gtksourceview/gtksourcecompletionprovider.c
+++ b/gtksourceview/gtksourcecompletionprovider.c
@@ -27,6 +27,12 @@
  * @short_description: Completion provider interface
  *
  * You must implement this interface to provide proposals to #GtkSourceCompletion
+ *
+ * The provider may be displayed in the completion window as a header row, showing
+ * its name and optionally an icon.
+ * The icon may be specified as a #GdkPixbuf, as an icon name or as a #GIcon by
+ * implementing the corresponding get function. Only one of those get functions
+ * should return a value different from %NULL.
  */
 
 #include "gtksourcecompletionprovider.h"