[gtk+] aboutdialog: Fix code snippets

[Timm Bäder <baedert src gnome org>]

commit bec55e216c6fa62cd3b3d76ff1bdc56cec995e8d
Author: Timm Bäder <mail baedert org>
Date:   Wed Oct 11 12:55:01 2017 +0200

    aboutdialog: Fix code snippets
    
    Define all variables and fix a missing comma in the first
    gtk_show_about_dialog call.

 gtk/gtkaboutdialog.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkaboutdialog.c b/gtk/gtkaboutdialog.c
index 23482c6..1f09c02 100644
--- a/gtk/gtkaboutdialog.c
+++ b/gtk/gtkaboutdialog.c
@@ -90,10 +90,11 @@
  * set the title property explicitly when constructing a GtkAboutDialog,
  * as shown in the following example:
  * |[<!-- language="C" -->
+ * GdkPixbuf *example_logo = gdk_pixbuf_new_from_file ("./logo.png", NULL);
  * gtk_show_about_dialog (NULL,
  *                        "program-name", "ExampleCode",
  *                        "logo", example_logo,
- *                        "title" _("About ExampleCode"),
+ *                        "title", _("About ExampleCode"),
  *                        NULL);
  * ]|
  *
@@ -1771,7 +1772,8 @@ gtk_about_dialog_get_translator_credits (GtkAboutDialog *about)
  * Using gettext(), a simple way to achieve that is to mark the
  * string for translation:
  * |[<!-- language="C" -->
- *  gtk_about_dialog_set_translator_credits (about,
+ * GtkWidget *about = gtk_about_dialog_new ();
+ *  gtk_about_dialog_set_translator_credits (GTK_ABOUT_DIALOG (about),
  *                                           _("translator-credits"));
  * ]|
  * It is a good idea to use the customary msgid “translator-credits” for this