[gegl] gegl: add workaroud for interpolation of first keyframed frame

[Øyvind Kolås <ok src gnome org>]

commit 0e6b0d4500fdc2649d3438121e2cf9be06079c4e
Author: Øyvind Kolås <pippin gimp org>
Date:   Fri Apr 21 14:20:10 2017 +0200

    gegl: add workaroud for interpolation of first keyframed frame

 gegl/gegl-serialize.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gegl/gegl-serialize.c b/gegl/gegl-serialize.c
index e39570b..a7fb3ce 100644
--- a/gegl/gegl-serialize.c
+++ b/gegl/gegl-serialize.c
@@ -110,6 +110,8 @@ gegl_create_chain_argv (char    **ops,
           if (strchr (*arg, '}'))
             {
               gdouble y = 0;
+              if (time == 0.0) /* avoiding ugly start interpolation artifact */
+                time = 0.4;
               gegl_path_calc_y_for_x (g_object_get_qdata (G_OBJECT (new),
                                                           g_quark_from_string(
                                                             prop)), time, &y);