[gtk+] Add some more documentation about GDK_SCROLL_SMOOTH

[Matthias Clasen <matthiasc src gnome org>]

commit 3be5c09a9055b04d5d5a4272fd12f854ca20a571
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Apr 30 22:28:08 2012 -0400

    Add some more documentation about GDK_SCROLL_SMOOTH

 README.in       |    5 ++++-
 gdk/gdkevents.h |    8 +++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)
---
diff --git a/README.in b/README.in
index 9622de6..0fe846d 100644
--- a/README.in
+++ b/README.in
@@ -96,7 +96,10 @@ Release notes for 3.4
 * Scroll events have been separated from button events, and smooth
   scrolling has been added with a separate event mask. Widgets now
   need to have either GDK_SCROLL_MASK or GDK_SMOOTH_SCROLL_MASK in
-  their event mask to receive scroll events.
+  their event mask to receive scroll events. In addition, the
+  GdkScrollDirection enumeration has gained a new member,
+  GDK_SCROLL_SMOOTH, so switch statements will have to be amended
+  to cover this case.
 
 * GTK+ now uses <Primary> instead of <Control> in keyboard accelerators,
   for improved cross-platform handling. This should not affect
diff --git a/gdk/gdkevents.h b/gdk/gdkevents.h
index 4c42678..73c9e83 100644
--- a/gdk/gdkevents.h
+++ b/gdk/gdkevents.h
@@ -736,7 +736,8 @@ struct _GdkEventTouch
  *   the modifier keys (e.g. Control, Shift and Alt) and the pointer
  *   buttons. See #GdkModifierType.
  * @direction: the direction to scroll to (one of %GDK_SCROLL_UP,
- *   %GDK_SCROLL_DOWN, %GDK_SCROLL_LEFT and %GDK_SCROLL_RIGHT).
+ *   %GDK_SCROLL_DOWN, %GDK_SCROLL_LEFT, %GDK_SCROLL_RIGHT or
+ *   %GDK_SCROLL_SMOOTH).
  * @device: the device where the event originated.
  * @x_root: the x coordinate of the pointer relative to the root of the
  *   screen.
@@ -746,6 +747,11 @@ struct _GdkEventTouch
  * Generated from button presses for the buttons 4 to 7. Wheel mice are
  * usually configured to generate button press events for buttons 4 and 5
  * when the wheel is turned.
+ *
+ * Some GDK backends can also generate 'smooth' scroll events, which
+ * can be recognized by the %GDK_SCROLL_SMOOTH scroll direction. For
+ * these, the scroll deltas can be obtained with
+ * gdk_event_get_scroll_deltas().
  */
 struct _GdkEventScroll
 {