[gtk+] docs: Clarify the visibility of buttons in GtkStackSwitcher

[Daniel Boles <dboles src gnome org>]

commit eaae832697658601cebe410d3533e89854e38e74
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Oct 10 10:19:53 2017 +0100

    docs: Clarify the visibility of buttons in GtkStackSwitcher
    
    If a page in the GtkStack is not visible, then the GtkStackSwitcher
    won't show a button for it.

 gtk/gtkstackswitcher.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkstackswitcher.c b/gtk/gtkstackswitcher.c
index 19c887f..77d5670 100644
--- a/gtk/gtkstackswitcher.c
+++ b/gtk/gtkstackswitcher.c
@@ -39,10 +39,12 @@
  * the various pages of the associated stack widget.
  *
  * All the content for the buttons comes from the child properties
- * of the #GtkStack.
+ * of the #GtkStack; the button visibility in a #GtkStackSwitcher
+ * widget is controlled by the visibility of the child in the
+ * #GtkStack.
  *
  * It is possible to associate multiple #GtkStackSwitcher widgets
- * with the same stack widget.
+ * with the same #GtkStack widget.
  *
  * The GtkStackSwitcher widget was added in 3.10.
  *