Expand gtk_init docs

Make it clear that some aspects of GApplication
functionality happen before startup.

Fixes: #5781

diff --git a/gtk/gtkmain.c b/gtk/gtkmain.c
index 85f90f1e4b76744e1a665511845c6dc547bf113d..9c07e3d652ea14a9c97d2f8f7abfc3806544bcdb 100644 (file)
--- a/gtk/gtkmain.c
+++ b/gtk/gtkmain.c
@@ -637,8 +637,10 @@ gtk_init_check (void)
  * applications. It will initialize everything needed to operate the
  * toolkit.
  *
- * If you are using `GtkApplication`, you don't have to call this
- * function; the `GApplication::startup` handler does it for you.
+ * If you are using `GtkApplication`, you usually don't have to call this
+ * function; the `GApplication::startup` handler does it for you. Though,
+ * if you are using GApplication methods that will be invoked before `startup`,
+ * such as `local_command_line`, you may need to initialize stuff explicitly.
  *
  * This function will terminate your program if it was unable to
  * initialize the windowing system for some reason. If you want