Add GtkGestureZoom

This gesture interprets and reports relative scale differences when fed
with events from two different GdkEventSequences.

1 files changed, 201 insertions, 0 deletions

diff --git a/gtk/gtkgesturezoom.c b/gtk/gtkgesturezoom.c
new file mode 100644
index 0000000000..f242d6d4eb
--- /dev/null
+++ b/gtk/gtkgesturezoom.c
@@ -0,0 +1,201 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2012, One Laptop Per Child.
+ * Copyright (C) 2014, Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author(s): Carlos Garnacho <carlosg@gnome.org>
+ */
+#include "config.h"
+#include <math.h>
+#include <gtk/gtkgesturezoom.h>
+
+typedef struct _GtkGestureZoomPrivate GtkGestureZoomPrivate;
+
+enum {
+  SCALE_CHANGED,
+  LAST_SIGNAL
+};
+
+struct _GtkGestureZoomPrivate
+{
+  gdouble initial_distance;
+};
+
+static guint signals[LAST_SIGNAL] = { 0 };
+
+G_DEFINE_TYPE_WITH_PRIVATE (GtkGestureZoom, gtk_gesture_zoom, GTK_TYPE_GESTURE)
+
+static void
+gtk_gesture_zoom_init (GtkGestureZoom *gesture)
+{
+}
+
+static GObject *
+gtk_gesture_zoom_constructor (GType                  type,
+                              guint                  n_construct_properties,
+                              GObjectConstructParam *construct_properties)
+{
+  GObject *object;
+
+  object = G_OBJECT_CLASS (gtk_gesture_zoom_parent_class)->constructor (type,
+                                                                        n_construct_properties,
+                                                                        construct_properties);
+  g_object_set (object, "n-points", 2, NULL);
+
+  return object;
+}
+
+static gboolean
+_gtk_gesture_zoom_get_distance (GtkGestureZoom *zoom,
+                                gdouble        *distance)
+{
+  gdouble x1, y1, x2, y2;
+  GtkGesture *gesture;
+  GList *sequences;
+  gdouble dx, dy;
+
+  gesture = GTK_GESTURE (zoom);
+
+  if (!gtk_gesture_is_recognized (gesture))
+    return FALSE;
+
+  sequences = gtk_gesture_get_sequences (gesture);
+  g_assert (sequences && sequences->next);
+
+  gtk_gesture_get_point (gesture, sequences->data, &x1, &y1);
+  gtk_gesture_get_point (gesture, sequences->next->data, &x2, &y2);
+  g_list_free (sequences);
+
+  dx = x1 - x2;
+  dy = y1 - y2;;
+  *distance = sqrt ((dx * dx) + (dy * dy));
+
+  return TRUE;
+}
+
+static gboolean
+_gtk_gesture_zoom_check_emit (GtkGestureZoom *gesture)
+{
+  GtkGestureZoomPrivate *priv;
+  gdouble distance, zoom;
+
+  if (!_gtk_gesture_zoom_get_distance (gesture, &distance))
+    return FALSE;
+
+  priv = gtk_gesture_zoom_get_instance_private (gesture);
+
+  if (distance == 0 || priv->initial_distance == 0)
+    return FALSE;
+
+  zoom = distance / priv->initial_distance;
+  g_signal_emit (gesture, signals[SCALE_CHANGED], 0, zoom);
+
+  return TRUE;
+}
+
+static void
+gtk_gesture_zoom_begin (GtkGesture       *gesture,
+                        GdkEventSequence *sequence)
+{
+  GtkGestureZoom *zoom = GTK_GESTURE_ZOOM (gesture);
+  GtkGestureZoomPrivate *priv;
+
+  priv = gtk_gesture_zoom_get_instance_private (zoom);
+  _gtk_gesture_zoom_get_distance (zoom, &priv->initial_distance);
+}
+
+static void
+gtk_gesture_zoom_update (GtkGesture       *gesture,
+                         GdkEventSequence *sequence)
+{
+  _gtk_gesture_zoom_check_emit (GTK_GESTURE_ZOOM (gesture));
+}
+
+static void
+gtk_gesture_zoom_class_init (GtkGestureZoomClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GtkGestureClass *gesture_class = GTK_GESTURE_CLASS (klass);
+
+  object_class->constructor = gtk_gesture_zoom_constructor;
+
+  gesture_class->begin = gtk_gesture_zoom_begin;
+  gesture_class->update = gtk_gesture_zoom_update;
+
+  /**
+   * GtkGestureZoom::scale-changed:
+   * @controller: the object on which the signal is emitted
+   * @scale: Scale delta, taking the initial state as 1:1
+   */
+  signals[SCALE_CHANGED] =
+    g_signal_new ("scale-changed",
+                  GTK_TYPE_GESTURE_ZOOM,
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GtkGestureZoomClass, scale_changed),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 1, G_TYPE_DOUBLE);
+}
+
+/**
+ * gtk_gesture_zoom_new:
+ * @widget: a #GtkWidget
+ *
+ * Returns a newly created #GtkGesture that recognizes zoom
+ * in/out gestures (usually known as pinch/zoom)
+ *
+ * Returns: a newly created #GtkGestureZoom
+ *
+ * Since: 3.14
+ **/
+GtkGesture *
+gtk_gesture_zoom_new (GtkWidget *widget)
+{
+  return g_object_new (GTK_TYPE_GESTURE_ZOOM,
+                       "widget", widget,
+                       NULL);
+}
+
+/**
+ * gtk_gesture_zoom_get_scale_delta:
+ * @gesture: a #GtkGestureZoom
+ * @scale: (out) (transfer none): zoom delta
+ *
+ * If @controller is active, this function returns %TRUE and fills
+ * in @scale with the zooming difference since the gesture was
+ * recognized (hence the starting point is considered 1:1).
+ *
+ * Returns: %TRUE if @controller is recognizing a zoom gesture
+ *
+ * Since: 3.14
+ **/
+gboolean
+gtk_gesture_zoom_get_scale_delta (GtkGestureZoom *gesture,
+                                  gdouble        *scale)
+{
+  GtkGestureZoomPrivate *priv;
+  gdouble distance;
+
+  g_return_val_if_fail (GTK_IS_GESTURE_ZOOM (gesture), FALSE);
+
+  if (!_gtk_gesture_zoom_get_distance (gesture, &distance))
+    return FALSE;
+
+  priv = gtk_gesture_zoom_get_instance_private (gesture);
+
+  if (scale)
+    *scale = distance / priv->initial_distance;
+
+  return TRUE;
+}