[gnome-calendar/ui-rewrite] gcal-viewport: added :scroll_to method

[Erick Pérez Castellanos <erickpc src gnome org>]

commit 18e9278a229e36238b80cd1f0e831618a2ae12c4
Author: Erick Pérez Castellanos <erick red gmail com>
Date:   Tue Jun 18 09:21:45 2013 -0400

    gcal-viewport: added :scroll_to method
    
    GcalViewport:scroll_to will scroll to a point of it
    children accordingly to a value passed

 src/gcal-viewport.c |   28 ++++++++++++++++++++++++++++
 src/gcal-viewport.h |    3 +++
 2 files changed, 31 insertions(+), 0 deletions(-)
---
diff --git a/src/gcal-viewport.c b/src/gcal-viewport.c
index 87dca1a..a6f0973 100644
--- a/src/gcal-viewport.c
+++ b/src/gcal-viewport.c
@@ -253,3 +253,31 @@ gcal_viewport_add (GcalViewport *viewport,
   g_signal_connect_after (widget, "size-allocate",
                           G_CALLBACK (gcal_viewport_child_allocated), viewport);
 }
+
+/**
+ * gcal_viewport_scroll_to:
+ * @viewport: a #GcalViewport
+ * @value: a value between 0 and 1.0 for scrolling the child.
+ *
+ * If no scrollbar is shown, this method does nothing
+ **/
+void
+gcal_viewport_scroll_to (GcalViewport *viewport,
+                         gdouble       value)
+{
+  GcalViewportPrivate *priv;
+  GtkAdjustment *adj;
+  gdouble lower, upper, page_size;
+
+  priv = viewport->priv;
+
+  value = CLAMP (value, 0.0, 1.0);
+
+  adj = gtk_range_get_adjustment (GTK_RANGE (priv->vscrollbar));
+  page_size = gtk_adjustment_get_page_size (adj);
+  lower = gtk_adjustment_get_lower (adj);
+  upper = gtk_adjustment_get_upper (adj);
+
+  value = ((upper - page_size) - lower) * value;
+  gtk_adjustment_set_value (adj, value);
+}
diff --git a/src/gcal-viewport.h b/src/gcal-viewport.h
index fe659c1..e237fca 100644
--- a/src/gcal-viewport.h
+++ b/src/gcal-viewport.h
@@ -55,6 +55,9 @@ GtkWidget*     gcal_viewport_new                       (void);
 void           gcal_viewport_add                       (GcalViewport *viewport,
                                                        GtkWidget    *widget);
 
+void           gcal_viewport_scroll_to                 (GcalViewport *viewport,
+                                                       gdouble       value);
+
 G_END_DECLS
 
 #endif /* __GCAL_VIEWPORT_H__ */