[gegl] text: fix handling of zero alpha values

[N/A <ell src gnome org>]

commit 13e4f8a034d0af1521ddb22ad939ed6102c39e60
Author: Ell <ell_se yahoo com>
Date:   Fri Dec 23 08:13:32 2016 -0500

    text: fix handling of zero alpha values

 operations/external/text.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/operations/external/text.c b/operations/external/text.c
index babe4c1..04646d2 100644
--- a/operations/external/text.c
+++ b/operations/external/text.c
@@ -182,9 +182,13 @@ static void text_layout_text (GeglOp        *self,
     }
   else
     {
-      cairo_translate (cr, 0, vertical_offset);
+      /* When alpha is 0, Pango goes full alpha (by design).  Go figure... */
+      if (color[3] > 0)
+        {
+          cairo_translate (cr, 0, vertical_offset);
 
-      pango_cairo_show_layout (cr, layout);
+          pango_cairo_show_layout (cr, layout);
+        }
     }
 
   pango_font_description_free (desc);