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[gnome-photos/wip/rishi/gesture-zoom: 11/12] Add PhotosGestureZoom

commit 6f360e1524c148dd7f24291d208ce5f427b6f7ab
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Oct 16 15:47:14 2017 +0200

    Add PhotosGestureZoom
    
    It is meant to extend GtkGestureZoom by resetting the initial distance
    whenever the touch points change direction.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=783922

 src/Makefile.am             |    4 +
 src/photos-enums.c.template |    1 +
 src/photos-gesture-zoom.c   |  275 +++++++++++++++++++++++++++++++++++++++++++
 src/photos-gesture-zoom.h   |   48 ++++++++
 src/photos-marshalers.list  |    1 +
 5 files changed, 329 insertions(+), 0 deletions(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index f8ff96a..543f1c9 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -112,6 +112,8 @@ gnome_photos_SOURCES = \
        photos-flickr-item.h \
        photos-gegl.c \
        photos-gegl.h \
+       photos-gesture-zoom.c \
+       photos-gesture-zoom.h \
        photos-glib.c \
        photos-glib.h \
        photos-google-item.c \
@@ -504,6 +506,7 @@ stamp-photos-enums.h: photos-enums.h.template
        $(AM_V_GEN) ( \
                ( glib-mkenums \
                        --template $(srcdir)/photos-enums.h.template \
+                        $(srcdir)/photos-gesture-zoom.h \
                         $(srcdir)/photos-item-manager.h \
                         $(srcdir)/photos-operation-insta-common.h \
                         $(srcdir)/photos-utils.h \
@@ -517,6 +520,7 @@ photos-enums.c: photos-enums.c.template
        $(AM_V_GEN) ( \
                ( glib-mkenums \
                        --template $(srcdir)/photos-enums.c.template \
+                        $(srcdir)/photos-gesture-zoom.h \
                         $(srcdir)/photos-item-manager.h \
                         $(srcdir)/photos-operation-insta-common.h \
                         $(srcdir)/photos-utils.h \
diff --git a/src/photos-enums.c.template b/src/photos-enums.c.template
index e93d20d..07880a8 100644
--- a/src/photos-enums.c.template
+++ b/src/photos-enums.c.template
@@ -3,6 +3,7 @@
 #include "config.h"
 
 #include "photos-enums.h"
+#include "photos-gesture-zoom.h"
 #include "photos-item-manager.h"
 #include "photos-operation-insta-common.h"
 #include "photos-utils.h"
diff --git a/src/photos-gesture-zoom.c b/src/photos-gesture-zoom.c
new file mode 100644
index 0000000..8b63573
--- /dev/null
+++ b/src/photos-gesture-zoom.c
@@ -0,0 +1,275 @@
+/*
+ * Photos - access, organize and share your photos on GNOME
+ * Copyright © 2017 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+
+#include "config.h"
+
+#include <math.h>
+
+#include "photos-enums.h"
+#include "photos-gesture-zoom.h"
+#include "photos-marshalers.h"
+#include "photos-utils.h"
+
+
+struct _PhotosGestureZoom
+{
+  GObject parent_instance;
+  GtkGesture *gesture;
+  PhotosGestureZoomDirection previous_direction;
+  gdouble initial_distance;
+  gdouble previous_distance;
+};
+
+enum
+{
+  PROP_0,
+  PROP_GESTURE
+};
+
+enum
+{
+  DIRECTION_CHANGED,
+  SCALE_CHANGED,
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL] = { 0 };
+
+
+G_DEFINE_TYPE (PhotosGestureZoom, photos_gesture_zoom, G_TYPE_OBJECT);
+
+
+static gdouble
+photos_gesture_zoom_calculate_distance (PhotosGestureZoom *self, GdkTouchpadGesturePhase touchpad_phase)
+{
+  GList *sequences = NULL;
+  const GdkEvent *last_event;
+  gdouble ret_val = -1.0;
+
+  g_return_val_if_fail (gtk_gesture_is_recognized (self->gesture), -1.0);
+
+  sequences = gtk_gesture_get_sequences (self->gesture);
+  g_return_val_if_fail (sequences != NULL, -1.0);
+
+  last_event = gtk_gesture_get_last_event (self->gesture, (GdkEventSequence *) sequences->data);
+  if (last_event->type == GDK_TOUCHPAD_PINCH
+      && (GdkTouchpadGesturePhase) last_event->touchpad_pinch.phase == touchpad_phase)
+    {
+      ret_val = last_event->touchpad_pinch.scale;
+    }
+  else
+    {
+      gdouble distance2;
+      gdouble x1;
+      gdouble x2;
+      gdouble y1;
+      gdouble y2;
+
+      g_assert_nonnull (sequences->next);
+
+      gtk_gesture_get_point (self->gesture, (GdkEventSequence *) sequences->data, &x1, &y1);
+      gtk_gesture_get_point (self->gesture, (GdkEventSequence *) sequences->next->data, &x2, &y2);
+
+      distance2 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+      ret_val = sqrt (distance2);
+    }
+
+  g_list_free (sequences);
+  return ret_val;
+}
+
+
+static void
+photos_gesture_zoom_begin (PhotosGestureZoom *self)
+{
+  g_return_if_fail (PHOTOS_IS_GESTURE_ZOOM (self));
+  g_return_if_fail (gtk_gesture_is_recognized (self->gesture));
+
+  self->initial_distance = photos_gesture_zoom_calculate_distance (self, GDK_TOUCHPAD_GESTURE_PHASE_BEGIN);
+  g_return_if_fail (self->initial_distance >= 0.0);
+
+  self->previous_direction = PHOTOS_GESTURE_ZOOM_DIRECTION_NONE;
+  self->previous_distance = self->initial_distance;
+}
+
+
+static void
+photos_gesture_zoom_update (PhotosGestureZoom *self)
+{
+  PhotosGestureZoomDirection direction;
+  gdouble distance;
+  gdouble scale;
+
+  g_return_if_fail (PHOTOS_IS_GESTURE_ZOOM (self));
+  g_return_if_fail ((self->previous_direction == PHOTOS_GESTURE_ZOOM_DIRECTION_NONE
+                     && photos_utils_equal_double (self->initial_distance, self->previous_distance))
+                    || (self->previous_direction != PHOTOS_GESTURE_ZOOM_DIRECTION_NONE
+                        && !photos_utils_equal_double (self->initial_distance, self->previous_distance)));
+
+  distance = photos_gesture_zoom_calculate_distance (self, GDK_TOUCHPAD_GESTURE_PHASE_UPDATE);
+  g_return_if_fail (distance >= 0.0);
+
+  if (photos_utils_equal_double (distance, self->previous_distance))
+    goto out;
+
+  if (self->previous_distance > distance)
+    direction = PHOTOS_GESTURE_ZOOM_DIRECTION_DECREASING;
+  else
+    direction = PHOTOS_GESTURE_ZOOM_DIRECTION_INCREASING;
+
+  if (self->previous_direction != PHOTOS_GESTURE_ZOOM_DIRECTION_NONE && self->previous_direction != 
direction)
+    {
+      self->initial_distance = self->previous_distance;
+      g_signal_emit (self, signals[DIRECTION_CHANGED], 0);
+    }
+
+  scale = distance / self->initial_distance;
+  g_signal_emit (self, signals[SCALE_CHANGED], 0, scale, direction);
+
+  self->previous_direction = direction;
+
+ out:
+  self->previous_distance = distance;
+}
+
+
+static void
+photos_gesture_zoom_constructed (GObject *object)
+{
+  PhotosGestureZoom *self = PHOTOS_GESTURE_ZOOM (object);
+
+  G_OBJECT_CLASS (photos_gesture_zoom_parent_class)->constructed (object);
+
+  g_signal_connect_object (self->gesture, "begin", G_CALLBACK (photos_gesture_zoom_begin), self, 
G_CONNECT_SWAPPED);
+  g_signal_connect_object (self->gesture, "update", G_CALLBACK (photos_gesture_zoom_update), self, 
G_CONNECT_SWAPPED);
+}
+
+
+static void
+photos_gesture_zoom_dispose (GObject *object)
+{
+  PhotosGestureZoom *self = PHOTOS_GESTURE_ZOOM (object);
+
+  g_clear_object (&self->gesture);
+
+  G_OBJECT_CLASS (photos_gesture_zoom_parent_class)->dispose (object);
+}
+
+
+static void
+photos_gesture_zoom_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
+{
+  PhotosGestureZoom *self = PHOTOS_GESTURE_ZOOM (object);
+
+  switch (prop_id)
+    {
+    case PROP_GESTURE:
+      g_value_set_object (value, self->gesture);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+
+static void
+photos_gesture_zoom_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
+{
+  PhotosGestureZoom *self = PHOTOS_GESTURE_ZOOM (object);
+
+  switch (prop_id)
+    {
+    case PROP_GESTURE:
+      self->gesture = GTK_GESTURE (g_value_dup_object (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+
+static void
+photos_gesture_zoom_init (PhotosGestureZoom *self)
+{
+}
+
+
+static void
+photos_gesture_zoom_class_init (PhotosGestureZoomClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->constructed = photos_gesture_zoom_constructed;
+  object_class->dispose = photos_gesture_zoom_dispose;
+  object_class->get_property = photos_gesture_zoom_get_property;
+  object_class->set_property = photos_gesture_zoom_set_property;
+
+  g_object_class_install_property (object_class,
+                                   PROP_GESTURE,
+                                   g_param_spec_object ("gesture",
+                                                        "Gesture",
+                                                        "The GtkGesture whose behaviour will be extended",
+                                                        GTK_TYPE_GESTURE,
+                                                        G_PARAM_CONSTRUCT_ONLY
+                                                        | G_PARAM_READWRITE));
+
+  signals[DIRECTION_CHANGED] = g_signal_new ("direction-changed",
+                                             G_TYPE_FROM_CLASS (class),
+                                             G_SIGNAL_RUN_LAST,
+                                             0,
+                                             NULL, /* accumulator */
+                                             NULL, /* accu_data */
+                                             g_cclosure_marshal_VOID__VOID,
+                                             G_TYPE_NONE,
+                                             0);
+
+  signals[SCALE_CHANGED] = g_signal_new ("scale-changed",
+                                         G_TYPE_FROM_CLASS (class),
+                                         G_SIGNAL_RUN_LAST,
+                                         0,
+                                         NULL, /* accumulator */
+                                         NULL, /* accu_data */
+                                         _photos_marshal_VOID__DOUBLE_ENUM,
+                                         G_TYPE_NONE,
+                                         2,
+                                         G_TYPE_DOUBLE,
+                                         PHOTOS_TYPE_GESTURE_ZOOM_DIRECTION);
+}
+
+
+PhotosGestureZoom *
+photos_gesture_zoom_new (GtkGesture *gesture)
+{
+  g_return_val_if_fail (GTK_IS_GESTURE (gesture), NULL);
+  return g_object_new (PHOTOS_TYPE_GESTURE_ZOOM, "gesture", gesture, NULL);
+}
+
+
+GtkGesture *
+photos_gesture_zoom_get_gesture (PhotosGestureZoom *self)
+{
+  g_return_val_if_fail (PHOTOS_IS_GESTURE_ZOOM (self), NULL);
+  return self->gesture;
+}
diff --git a/src/photos-gesture-zoom.h b/src/photos-gesture-zoom.h
new file mode 100644
index 0000000..7f550cd
--- /dev/null
+++ b/src/photos-gesture-zoom.h
@@ -0,0 +1,48 @@
+/*
+ * Photos - access, organize and share your photos on GNOME
+ * Copyright © 2017 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef PHOTOS_GESTURE_ZOOM_H
+#define PHOTOS_GESTURE_ZOOM_H
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define PHOTOS_TYPE_GESTURE_ZOOM (photos_gesture_zoom_get_type ())
+G_DECLARE_FINAL_TYPE (PhotosGestureZoom,
+                      photos_gesture_zoom,
+                      PHOTOS,
+                      GESTURE_ZOOM,
+                      GObject);
+
+typedef enum
+{
+  PHOTOS_GESTURE_ZOOM_DIRECTION_NONE,
+  PHOTOS_GESTURE_ZOOM_DIRECTION_DECREASING,
+  PHOTOS_GESTURE_ZOOM_DIRECTION_INCREASING
+} PhotosGestureZoomDirection;
+
+PhotosGestureZoom    *photos_gesture_zoom_new                           (GtkGesture *gesture);
+
+GtkGesture           *photos_gesture_zoom_get_gesture                   (PhotosGestureZoom *self);
+
+G_END_DECLS
+
+#endif /* PHOTOS_GESTURE_ZOOM_H */
diff --git a/src/photos-marshalers.list b/src/photos-marshalers.list
index dbde703..ea1cd27 100644
--- a/src/photos-marshalers.list
+++ b/src/photos-marshalers.list
@@ -1,4 +1,5 @@
 VOID:BOXED,BOXED
+VOID:DOUBLE,ENUM
 VOID:ENUM,ENUM
 VOID:INT,INT
 VOID:STRING,STRING
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