[gtksourceview] SpaceDrawer: document use-case about drawing only unwanted spaces

[Sébastien Wilmet <swilmet src gnome org>]

commit 051f6a6e88aa82346e7aeef1a67d1a4c30eb6e6b
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Oct 19 13:05:09 2016 +0200

    SpaceDrawer: document use-case about drawing only unwanted spaces

 gtksourceview/gtksourcespacedrawer.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/gtksourceview/gtksourcespacedrawer.c b/gtksourceview/gtksourcespacedrawer.c
index e252746..e326d2e 100644
--- a/gtksourceview/gtksourcespacedrawer.c
+++ b/gtksourceview/gtksourcespacedrawer.c
@@ -70,6 +70,15 @@
  *
  * gtk_source_space_drawer_set_enable_matrix (space_drawer, TRUE);
  * ]|
+ *
+ * # Use-case: draw unwanted white spaces
+ *
+ * A possible use-case is to draw only unwanted white spaces. Examples:
+ * - Draw all trailing spaces.
+ * - If the indentation and alignment must be done with spaces, draw tabs.
+ *
+ * And non-breaking spaces can always be drawn, everywhere, to distinguish them
+ * from normal spaces.
  */
 
 /* A drawer specially designed for the International Space Station. It comes by