[f-spot/FSPOT_0_6_0_STABLE] restore the slideshow transitions on gtk+-2.18

[Stephane Delcroix <sdelcroix src gnome org>]

commit 85448c38cff854b8c5e6b0bbd4916043d18d0278
Author: Stephane Delcroix <stephane delcroix org>
Date:   Thu Sep 24 22:04:00 2009 +0200

    restore the slideshow transitions on gtk+-2.18

 src/Widgets/SlideShow.cs |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/Widgets/SlideShow.cs b/src/Widgets/SlideShow.cs
index 7c8ce61..cf67ffb 100644
--- a/src/Widgets/SlideShow.cs
+++ b/src/Widgets/SlideShow.cs
@@ -89,6 +89,7 @@ namespace FSpot.Widgets
 
 				if (animation.IsRunning)
 					animation.Stop ();
+				progress = 0;
 				animation.Start ();
 			}
 		}
@@ -124,8 +125,10 @@ namespace FSpot.Widgets
 		double progress = 0;
 		void HandleProgressChanged (double progress)
 		{
-			this.progress = progress;
-			QueueDraw ();
+			lock (sync_handle) {
+				this.progress = progress;
+				QueueDraw ();
+			}
 		}
 #endregion