[evince] libview: Ctrl+mouse wheel zoom should be pointer-centered, not window-centered

[Carlos Garcia Campos <carlosgc src gnome org>]

commit 9d9e14dfa9ae782e879961b7307f55b41b2a60b3
Author: Frédéric Moenne-loccoz <frederic moenne-loccoz sfr fr>
Date:   Sun Feb 15 11:14:30 2015 +0100

    libview: Ctrl+mouse wheel zoom should be pointer-centered, not window-centered
    
    https://bugzilla.gnome.org/show_bug.cgi?id=731669

 libview/ev-view-private.h |    4 ++++
 libview/ev-view.c         |   25 ++++++++++++++++++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)
---
diff --git a/libview/ev-view-private.h b/libview/ev-view-private.h
index c5efeaa..087f3ef 100644
--- a/libview/ev-view-private.h
+++ b/libview/ev-view-private.h
@@ -235,6 +235,10 @@ struct _EvView {
        GtkGesture *zoom_gesture;
        gdouble prev_zoom_gesture_scale;
        EvPanAction pan_action;
+
+       /* Current zoom center */
+       gdouble zoom_center_x;
+       gdouble zoom_center_y;
 };
 
 struct _EvViewClass {
diff --git a/libview/ev-view.c b/libview/ev-view.c
index a9159cd..3fc4584 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -607,6 +607,7 @@ ev_view_set_adjustment_values (EvView         *view,
        gdouble upper;
        double factor;
        gint new_value;
+       gdouble zoom_center;
 
        gtk_widget_get_allocation (widget, &allocation);
 
@@ -614,10 +615,12 @@ ev_view_set_adjustment_values (EvView         *view,
                req_size = view->requisition.width;
                alloc_size = allocation.width;
                adjustment = view->hadjustment;
+               zoom_center = view->zoom_center_x;
        } else {
                req_size = view->requisition.height;
                alloc_size = allocation.height;
                adjustment = view->vadjustment;
+               zoom_center = view->zoom_center_y;
        }
 
        if (!adjustment)
@@ -627,6 +630,8 @@ ev_view_set_adjustment_values (EvView         *view,
        value = gtk_adjustment_get_value (adjustment);
        upper = gtk_adjustment_get_upper (adjustment);
        page_size = gtk_adjustment_get_page_size (adjustment);
+       if (zoom_center < 0)
+               zoom_center = page_size * 0.5;
 
        if (upper != .0) {
                switch (view->pending_scroll) {
@@ -636,8 +641,8 @@ ev_view_set_adjustment_values (EvView         *view,
                        break;
                case SCROLL_TO_PAGE_POSITION:
                        break;
-               case SCROLL_TO_CENTER:
-                       factor = (value + page_size * 0.5) / upper;
+               case SCROLL_TO_CENTER:
+                       factor = (value + zoom_center) / upper;
                        break;
                }
        }
@@ -663,9 +668,12 @@ ev_view_set_adjustment_values (EvView         *view,
                case SCROLL_TO_PAGE_POSITION:
                        ev_view_scroll_to_page_position (view, orientation);
                        break;
-               case SCROLL_TO_CENTER:
-                       new_value = CLAMP (upper * factor - page_size * 0.5 + 0.5,
-                                          0, upper - page_size);
+               case SCROLL_TO_CENTER:
+                       new_value = CLAMP (upper * factor - zoom_center + 0.5, 0, upper - page_size);
+                       if (orientation == GTK_ORIENTATION_HORIZONTAL)
+                               view->zoom_center_x = -1.0;
+                       else
+                               view->zoom_center_y = -1.0;
                        gtk_adjustment_set_value (adjustment, (int)new_value);
                        break;
        }
@@ -3963,6 +3971,9 @@ ev_view_scroll_event (GtkWidget *widget, GdkEventScroll *event)
 
        if (state == GDK_CONTROL_MASK) {
                ev_document_model_set_sizing_mode (view->model, EV_SIZING_FREE);
+               view->zoom_center_x = event->x;
+               view->zoom_center_y = event->y;
+
                switch (event->direction) {
                case GDK_SCROLL_DOWN:
                case GDK_SCROLL_RIGHT:
@@ -7167,6 +7178,8 @@ zoom_gesture_scale_changed_cb (GtkGestureZoom *gesture,
        view->prev_zoom_gesture_scale = scale;
        ev_document_model_set_sizing_mode (view->model, EV_SIZING_FREE);
 
+       gtk_gesture_get_bounding_box_center (GTK_GESTURE (gesture), &view->zoom_center_x, 
&view->zoom_center_y);
+
        if ((factor < 1.0 && ev_view_can_zoom_out (view)) ||
            (factor >= 1.0 && ev_view_can_zoom_in (view)))
                ev_view_zoom (view, factor);
@@ -7223,6 +7236,8 @@ ev_view_init (EvView *view)
        view->caret_enabled = FALSE;
        view->cursor_page = 0;
        view->allow_links_change_zoom = TRUE;
+       view->zoom_center_x = -1;
+       view->zoom_center_y = -1;
 
        g_signal_connect (view, "notify::scale-factor",
                          G_CALLBACK (on_notify_scale_factor), NULL);