[glide] Docs and guards for PDF exporter

[Robert Carr <racarr src gnome org>]

commit 15ea9a7699d6300c7c59f8ff4f699be80d8d4e6a
Author: Robert Carr <racarr Valentine localdomain>
Date:   Fri May 7 15:49:57 2010 -0400

    Docs and guards for PDF exporter

 libglide/glide-pdf-exporter.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/libglide/glide-pdf-exporter.c b/libglide/glide-pdf-exporter.c
index 4ccf5fd..65e5c27 100644
--- a/libglide/glide-pdf-exporter.c
+++ b/libglide/glide-pdf-exporter.c
@@ -75,8 +75,18 @@ glide_pdf_exporter_response_callback (GtkDialog *dialog,
   gtk_widget_destroy (GTK_WIDGET (dialog));
 }
 
+/**
+ * glide_pdf_exporter_export:
+ * @document: A #GlideDocument
+ *
+ * Displays a file selection dialog and exports @document to
+ * the selected file in PDF format.
+ *
+ */
 void
 glide_pdf_exporter_export (GlideDocument *document)
 {
+  g_return_if_fail (GLIDE_IS_DOCUMENT (document));
+
   glide_gtk_util_show_save_dialog (G_CALLBACK (glide_pdf_exporter_response_callback), document);
 }