[devhelp] DhLink: improve dh_link_type_compare()

[Sébastien Wilmet <swilmet src gnome org>]

commit c4ad058236480afe759fd1f262669f7af4367cd4
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Dec 7 17:01:15 2017 +0100

    DhLink: improve dh_link_type_compare()

 src/dh-link.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/src/dh-link.c b/src/dh-link.c
index f1dadb3..493c160 100644
--- a/src/dh-link.c
+++ b/src/dh-link.c
@@ -439,12 +439,17 @@ dh_link_type_compare (DhLinkType a,
         if (a == b)
                 return 0;
 
-        /* Sort page links before other links. The page is more important than a
-         * symbol (typically contained in that page).
+        /* Same order as in a tree: first the top-level book node, then pages,
+         * then keywords (keywords are contained in a page).
          */
-        if (a == DH_LINK_TYPE_PAGE)
+
+        if (a == DH_LINK_TYPE_BOOK)
                 return -1;
+        if (b == DH_LINK_TYPE_BOOK)
+                return 1;
 
+        if (a == DH_LINK_TYPE_PAGE)
+                return -1;
         if (b == DH_LINK_TYPE_PAGE)
                 return 1;