[evince] ev-view: Add pinch/zoom gesture to handle document zooming

[Carlos Garnacho <carlosg src gnome org>]

commit 36c7f21f5c0f96cd5f4761aa5c99c6e9f4bff861
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Mar 28 19:55:03 2014 +0100

    ev-view: Add pinch/zoom gesture to handle document zooming
    
    This is delegated on a GtkGestureZoom. When triggered, the document
    will be zoomed based on the distance changes between both fingers.
    When the gesture is not active, regular event handling (text selection,
    clicking, etc...) will happen.

 libview/ev-view-private.h |    4 +++
 libview/ev-view.c         |   50 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 1 deletions(-)
---
diff --git a/libview/ev-view-private.h b/libview/ev-view-private.h
index 7727bbb..66a47c4 100644
--- a/libview/ev-view-private.h
+++ b/libview/ev-view-private.h
@@ -222,6 +222,10 @@ struct _EvView {
        gboolean cursor_visible;
        guint    cursor_blink_timeout_id;
        guint    cursor_blink_time;
+
+       /* Gestures */
+       GtkGesture *zoom_gesture;
+       gdouble prev_zoom_gesture_scale;
 };
 
 struct _EvViewClass {
diff --git a/libview/ev-view.c b/libview/ev-view.c
index 4b64e22..1737139 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -4707,7 +4707,10 @@ ev_view_button_press_event (GtkWidget      *widget,
 
        if (!view->document)
                return FALSE;
-       
+
+       if (gtk_gesture_is_recognized (view->zoom_gesture))
+               return TRUE;
+
        if (!gtk_widget_has_focus (widget)) {
                gtk_widget_grab_focus (widget);
        }
@@ -5028,6 +5031,9 @@ ev_view_motion_notify_event (GtkWidget      *widget,
        if (!view->document)
                return FALSE;
 
+       if (gtk_gesture_is_recognized (view->zoom_gesture))
+               return TRUE;
+
        window = gtk_widget_get_window (widget);
 
         if (event->is_hint || event->window != window) {
@@ -5184,6 +5190,9 @@ ev_view_button_release_event (GtkWidget      *widget,
 
        view->image_dnd_info.in_drag = FALSE;
 
+       if (gtk_gesture_is_recognized (view->zoom_gesture))
+               return TRUE;
+
        if (view->scroll_info.autoscrolling) {
                ev_view_autoscroll_stop (view);
                view->pressed_button = -1;
@@ -6303,6 +6312,8 @@ ev_view_finalize (GObject *object)
                g_object_unref (view->image_dnd_info.image);
        view->image_dnd_info.image = NULL;
 
+       g_object_unref (view->zoom_gesture);
+
        G_OBJECT_CLASS (ev_view_parent_class)->finalize (object);
 }
 
@@ -6986,6 +6997,33 @@ on_notify_scale_factor (EvView     *view,
 }
 
 static void
+zoom_gesture_begin_cb (GtkGesture       *gesture,
+                      GdkEventSequence *sequence,
+                      EvView           *view)
+{
+       view->prev_zoom_gesture_scale = 1;
+}
+
+static void
+zoom_gesture_scale_changed_cb (GtkGestureZoom *gesture,
+                              gdouble         scale,
+                              EvView         *view)
+{
+       gdouble factor;
+
+       view->drag_info.in_drag = FALSE;
+       view->image_dnd_info.in_drag = FALSE;
+
+       factor = scale - view->prev_zoom_gesture_scale + 1;
+       view->prev_zoom_gesture_scale = scale;
+       ev_document_model_set_sizing_mode (view->model, EV_SIZING_FREE);
+
+       if ((factor < 1.0 && ev_view_can_zoom_out (view)) ||
+           (factor >= 1.0 && ev_view_can_zoom_in (view)))
+               ev_view_zoom (view, factor);
+}
+
+static void
 ev_view_init (EvView *view)
 {
        GtkStyleContext *context;
@@ -7000,6 +7038,7 @@ ev_view_init (EvView *view)
        gtk_style_context_add_class (context, "view");
 
        gtk_widget_set_events (GTK_WIDGET (view),
+                              GDK_TOUCH_MASK |
                               GDK_EXPOSURE_MASK |
                               GDK_BUTTON_PRESS_MASK |
                               GDK_BUTTON_RELEASE_MASK |
@@ -7037,6 +7076,15 @@ ev_view_init (EvView *view)
 
        g_signal_connect (view, "notify::scale-factor",
                          G_CALLBACK (on_notify_scale_factor), NULL);
+
+       view->zoom_gesture = gtk_gesture_zoom_new (GTK_WIDGET (view));
+       gtk_event_controller_set_propagation_phase (GTK_EVENT_CONTROLLER (view->zoom_gesture),
+                                                   GTK_PHASE_CAPTURE);
+
+       g_signal_connect (view->zoom_gesture, "begin",
+                         G_CALLBACK (zoom_gesture_begin_cb), view);
+       g_signal_connect (view->zoom_gesture, "scale-changed",
+                         G_CALLBACK (zoom_gesture_scale_changed_cb), view);
 }
 
 /*** Callbacks ***/