[sysprof/wip/visualizers] visualizer-view: avoid overscroll upon zoom change

[Christian Hergert <chergert src gnome org>]

commit 5c53dd5d6e61db735c471ff81654a5302c33825e
Author: Christian Hergert <chergert redhat com>
Date:   Fri Sep 30 17:04:48 2016 -0700

    visualizer-view: avoid overscroll upon zoom change
    
    When changing the zoom (zooming out), we could potentially
    let the scrollbar be past the end. This looks pretty bad when
    the GtkWindow doesn't clip correctly.
    
    This just adjusts things so we push ourselves back into the
    visible area.

 lib/sp-visualizer-view.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/lib/sp-visualizer-view.c b/lib/sp-visualizer-view.c
index b0b9565..4be1efe 100644
--- a/lib/sp-visualizer-view.c
+++ b/lib/sp-visualizer-view.c
@@ -130,6 +130,9 @@ sp_visualizer_view_notify_zoom (SpVisualizerView *self,
   gint64 begin_time = 0.0;
   gint64 end_time;
   gdouble zoom;
+  gdouble page_size;
+  gdouble upper;
+  gdouble value;
 
   g_assert (SP_IS_VISUALIZER_VIEW (self));
   g_assert (SP_IS_ZOOM_MANAGER (zoom_manager));
@@ -144,6 +147,15 @@ sp_visualizer_view_notify_zoom (SpVisualizerView *self,
   sp_visualizer_view_set_time_range (self, begin_time, end_time);
   gtk_adjustment_set_page_size (priv->scroll_adjustment, end_time - begin_time);
 
+  g_object_get (priv->scroll_adjustment,
+                "page-size", &page_size,
+                "upper", &upper,
+                "value", &value,
+                NULL);
+
+  if (value + page_size > upper)
+    gtk_adjustment_set_value (priv->scroll_adjustment, upper - page_size);
+
   if (priv->reader != NULL)
     {
       gint64 real_range;