[evince/gestures: 1/2] ev-view: Add pinch/zoom gesture to handle document zooming

[Carlos Garnacho <carlosg src gnome org>]

commit 858ad769f3be4dd4382a4f382b9a2c8cf750c784
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         |   49 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletions(-)
---
diff --git a/libview/ev-view-private.h b/libview/ev-view-private.h
index 4f1721a..82cc241 100644
--- a/libview/ev-view-private.h
+++ b/libview/ev-view-private.h
@@ -221,6 +221,10 @@ struct _EvView {
        gboolean cursor_visible;
        guint    cursor_blink_timeout_id;
        guint    cursor_blink_time;
+
+       /* Gestures */
+       GtkGesture *zoom_gesture;
+       gdouble prev_zoom_scale;
 };
 
 struct _EvViewClass {
diff --git a/libview/ev-view.c b/libview/ev-view.c
index 039e0bf..acb7a7e 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -4633,7 +4633,10 @@ 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);
        }
@@ -4954,6 +4957,9 @@ 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) {
@@ -5110,6 +5116,9 @@ 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;
@@ -6193,6 +6202,9 @@ ev_view_finalize (GObject *object)
                g_object_unref (view->image_dnd_info.image);
        view->image_dnd_info.image = NULL;
 
+       gtk_gesture_detach (view->zoom_gesture);
+       g_object_unref (view->zoom_gesture);
+
        G_OBJECT_CLASS (ev_view_parent_class)->finalize (object);
 }
 
@@ -6712,6 +6724,33 @@ ev_view_class_init (EvViewClass *class)
 }
 
 static void
+zoom_gesture_begin_cb (GtkGesture       *gesture,
+                      GdkEventSequence *sequence,
+                      EvView           *view)
+{
+       view->prev_zoom_scale = 1;
+}
+
+static void
+zoom_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_scale + 1;
+       view->prev_zoom_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;
@@ -6726,6 +6765,7 @@ 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 |
@@ -6760,6 +6800,13 @@ ev_view_init (EvView *view)
        view->pixbuf_cache_size = DEFAULT_PIXBUF_CACHE_SIZE;
        view->caret_enabled = FALSE;
        view->cursor_page = 0;
+
+       view->zoom_gesture = gtk_gesture_zoom_new (GTK_WIDGET (view));
+       gtk_gesture_attach (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_scale_changed_cb), view);
 }
 
 /*** Callbacks ***/