[gtksourceview] docs: clarification of gtk_source_gutter_renderer_draw()

[Sébastien Wilmet <swilmet src gnome org>]

commit 55ff40271a86ca0e6d89e9a8e8277053ad90a9e3
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon Nov 24 18:43:08 2014 +0100

    docs: clarification of gtk_source_gutter_renderer_draw()
    
    "without padding or margin" can be interpreted differently: does it mean
    the padding is not taken into account so it actually _includes_ the
    padding, or does it mean that the padding is outside the
    background_area?
    
    It turns out that "without padding" meant that the padding is included
    in the area delimited by background_area.

 gtksourceview/gtksourcegutterrenderer.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/gtksourceview/gtksourcegutterrenderer.c b/gtksourceview/gtksourcegutterrenderer.c
index 2eb8277..e6a1318 100644
--- a/gtksourceview/gtksourcegutterrenderer.c
+++ b/gtksourceview/gtksourcegutterrenderer.c
@@ -827,16 +827,20 @@ gtk_source_gutter_renderer_begin (GtkSourceGutterRenderer *renderer,
  * @end: a #GtkTextIter
  * @state: a #GtkSourceGutterRendererState
  *
- * Main renderering method. Implementations should implement this method to
- * draw onto the cairo context. The @background_area indicates total area of
- * the cell (without padding or margin) to be drawn. The @cell_area indicates
- * the area where content can be drawn (text, images, etc).
+ * Main renderering method. Implementations should implement this method to draw
+ * onto the cairo context. The @background_area indicates the total area of the
+ * cell to be drawn. The @cell_area indicates the area where content can be
+ * drawn (text, images, etc).
+ *
+ * The @background_area is the @cell_area plus the padding on each side (two
+ * times the #GtkSourceGutterRenderer:xpad horizontally and two times the
+ * #GtkSourceGutterRenderer:ypad vertically, so that the @cell_area is centered
+ * inside @background_area).
  *
  * The @state argument indicates the current state of the renderer and should
  * be taken into account to properly draw the different possible states
  * (cursor, prelit, selected) if appropriate.
- *
- **/
+ */
 void
 gtk_source_gutter_renderer_draw (GtkSourceGutterRenderer      *renderer,
                                  cairo_t                      *cr,