summaryrefslogtreecommitdiff
path: root/gtk/gtkgesturezoom.c
blob: 02e5a086951c791c2b8dbd8b7037e8821d462e55 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
/* 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>
 */

/**
 * SECTION:gtkgesturezoom
 * @Short_description: Zoom gesture
 * @Title: GtkGestureZoom
 * @See_also: #GtkGestureRotate
 *
 * #GtkGestureZoom is a #GtkGesture implementation able to recognize
 * pinch/zoom gestures, whenever the distance between both tracked
 * sequences changes, the #GtkGestureZoom::scale-changed signal is
 * emitted to report the scale factor.
 */

#include "config.h"
#include <math.h>
#include "gtkgesturezoom.h"
#include "gtkgesturezoomprivate.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
   *
   * This signal is emitted whenever the distance between both tracked
   * sequences changes.
   *
   * Since: 3.14
   */
  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)
{
  g_return_val_if_fail (GTK_IS_WIDGET (widget), NULL);

  return g_object_new (GTK_TYPE_GESTURE_ZOOM,
                       "widget", widget,
                       NULL);
}

/**
 * gtk_gesture_zoom_get_scale_delta:
 * @gesture: a #GtkGestureZoom
 *
 * If @gesture is active, this function returns the zooming difference
 * since the gesture was recognized (hence the starting point is
 * considered 1:1). If @gesture is not active, 1 is returned.
 *
 * Returns: the scale delta
 *
 * Since: 3.14
 **/
gdouble
gtk_gesture_zoom_get_scale_delta (GtkGestureZoom *gesture)
{
  GtkGestureZoomPrivate *priv;
  gdouble distance;

  g_return_val_if_fail (GTK_IS_GESTURE_ZOOM (gesture), 1.0);

  if (!_gtk_gesture_zoom_get_distance (gesture, &distance))
    return 1.0;

  priv = gtk_gesture_zoom_get_instance_private (gesture);

  return distance / priv->initial_distance;
}