[gtk+/gestures] scrolledwindow: Handle directional cancellation if there is a single scroll direction

[Carlos Garnacho <carlosg src gnome org>]

commit 6723449afbd85d80f42191cfc764857491ab429a
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri May 16 18:35:45 2014 +0200

    scrolledwindow: Handle directional cancellation if there is a single scroll direction
    
    A pan gesture is optionally attached if there is only one scrolling direction, the pan
    gesture orientation is changed so movements tangential to the scroll direction get
    scrolling cancelled (The pan gesture is automatically denied when that happens, and
    that state change spreads to the others gestures in the group). If the pan direction
    happens in the expected directions, no cancellation happens, and scrolling eventually
    takes place.

 gtk/gtkscrolledwindow.c |   38 ++++++++++++++++++++++++++++++++++++--
 1 files changed, 36 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index cf17c55..dca4067 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -149,9 +149,13 @@ struct _GtkScrolledWindowPrivate
   gint     min_content_height;
 
   /* Kinetic scrolling */
-  GtkGesture *drag_gesture;
-  GtkGesture *swipe_gesture;
   GtkGesture *long_press_gesture;
+  GtkGesture *swipe_gesture;
+
+  /* These two gestures are mutually exclusive */
+  GtkGesture *drag_gesture;
+  GtkGesture *pan_gesture;
+
   gdouble drag_start_x;
   gdouble drag_start_y;
 
@@ -718,6 +722,30 @@ scrolled_window_long_press_cancelled_cb (GtkScrolledWindow *scrolled_window,
 }
 
 static void
+gtk_scrolled_window_check_attach_pan_gesture (GtkScrolledWindow *sw)
+{
+  GtkScrolledWindowPrivate *priv = sw->priv;
+
+  if (priv->kinetic_scrolling &&
+      ((priv->hscrollbar_visible && !priv->vscrollbar_visible) ||
+       (!priv->hscrollbar_visible && priv->vscrollbar_visible)))
+    {
+      GtkPanOrientation orientation;
+
+      if (priv->hscrollbar_visible)
+        orientation = GTK_PAN_ORIENTATION_HORIZONTAL;
+      else
+        orientation = GTK_PAN_ORIENTATION_VERTICAL;
+
+      gtk_gesture_pan_set_orientation (GTK_GESTURE_PAN (priv->pan_gesture),
+                                       orientation);
+      gtk_gesture_attach (priv->pan_gesture, GTK_PHASE_CAPTURE);
+    }
+  else
+    gtk_gesture_detach (priv->pan_gesture);
+}
+
+static void
 gtk_scrolled_window_init (GtkScrolledWindow *scrolled_window)
 {
   GtkWidget *widget = GTK_WIDGET (scrolled_window);
@@ -752,6 +780,10 @@ gtk_scrolled_window_init (GtkScrolledWindow *scrolled_window)
                             G_CALLBACK (scrolled_window_drag_end_cb),
                             scrolled_window);
 
+  priv->pan_gesture = gtk_gesture_pan_new (widget, GTK_PAN_ORIENTATION_VERTICAL);
+  gtk_gesture_group (priv->pan_gesture, priv->drag_gesture);
+  gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (priv->pan_gesture), 1);
+
   priv->swipe_gesture = gtk_gesture_swipe_new (widget);
   gtk_gesture_group (priv->swipe_gesture, priv->drag_gesture);
   gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (priv->swipe_gesture), 1);
@@ -1247,6 +1279,7 @@ gtk_scrolled_window_set_kinetic_scrolling (GtkScrolledWindow *scrolled_window,
     return;
 
   priv->kinetic_scrolling = kinetic_scrolling;
+  gtk_scrolled_window_check_attach_pan_gesture (scrolled_window);
 
   if (priv->kinetic_scrolling)
     {
@@ -2296,6 +2329,7 @@ gtk_scrolled_window_size_allocate (GtkWidget     *widget,
     }
 
   _gtk_scrolled_window_allocate_overshoot_window (scrolled_window);
+  gtk_scrolled_window_check_attach_pan_gesture (scrolled_window);
 }
 
 static gboolean