[gtk/wip/dboles/overlay-docs-3: 1/2] Overlay: Improve overly brief blurbs @ child props

[Daniel Boles <dboles src gnome org>]

commit 816b4b49ee2146151c0c042f105ff253f4054d96
Author: Daniel Boles <dboles src gmail com>
Date:   Wed Jun 12 17:52:58 2019 +0100

    Overlay: Improve overly brief blurbs @ child props
    
    Be a bit clearer about what :pass-through does, and point :index at the
    corresponding reorder_overlay() method that explains what an index means

 gtk/gtkoverlay.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkoverlay.c b/gtk/gtkoverlay.c
index be0788dfc6..5cf956d144 100644
--- a/gtk/gtkoverlay.c
+++ b/gtk/gtkoverlay.c
@@ -771,7 +771,8 @@ gtk_overlay_class_init (GtkOverlayClass *klass)
   /**
    * GtkOverlay:pass-through:
    *
-   * Pass through input, does not affect main child.
+   * Whether to pass input through the overlay child to the main child.
+   * (Of course, this has no effect when set on the main child itself.)
    *
    * Since: 3.18
    */
@@ -783,7 +784,8 @@ gtk_overlay_class_init (GtkOverlayClass *klass)
   /**
    * GtkOverlay:index:
    *
-   * The index of the overlay in the parent, -1 for the main child.
+   * The index of the overlay child in the parent (or -1 for the main child).
+   * See gtk_overlay_reorder_overlay().
    *
    * Since: 3.18
    */