[gtk/mainloop-cleanup: 11/11] docs: Mention gtk_main in the migration guide

[Matthias Clasen <matthiasc src gnome org>]

commit 3dbbd69e05c8e0514e0fa071da51eff3bca12189
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Feb 9 22:47:25 2020 -0500

    docs: Mention gtk_main in the migration guide

 docs/reference/gtk/migrating-3to4.xml | 13 +++++++++++++
 1 file changed, 13 insertions(+)
---
diff --git a/docs/reference/gtk/migrating-3to4.xml b/docs/reference/gtk/migrating-3to4.xml
index 9bb310534b..e08d97f316 100644
--- a/docs/reference/gtk/migrating-3to4.xml
+++ b/docs/reference/gtk/migrating-3to4.xml
@@ -199,6 +199,19 @@
       </para>
     </section>
 
+    <section>
+      <title>Stop using gtk_main() and related APIs</title>
+
+      <para>
+        GTK4 removes the gtk_main_ family of APIs. The recommended replacement
+        is GtkApplication, but you can also iterate the GLib mainloop directly,
+        using GMainContext APIs.
+      </para>
+      <para>
+        The replacement for gtk_events_pending() is g_main_context_pending(),
+        the replacement for gtk_main_iteration() is g_main_context_iteration().
+      </para>
+    </section>
   </section>
 
   <section>