[gdm] gdm-session: Calculate fallback session name without ".desktop"

[Ray Strode <halfline src gnome org>]

commit 9606bf42d179dde4fd913fcb9304e01560fd855e
Author: Iain Lane <iain orangesquash org uk>
Date:   Tue Sep 12 13:28:39 2017 +0100

    gdm-session: Calculate fallback session name without ".desktop"
    
    When the user has not ever selected a session from the selector, we will
    log them into the `fallback' session, which is calculated by looking at
    all installed sessions and picking the first one in the list.
    
    There is a bug that the visually selected session presented in the
    greeter can be different from the fallback session calculated inside
    GDM. This happens because the two sort sessions differently.
    
    Inside GDM we calculate the fallback session by comparing the full
    basename of the file:
    
    >>> GLib.strcmp0("gnome-xorg.desktop", "gnome.desktop")
    -1
    
    Whereas gnome-shell calls gdm_get_session_ids(), which returns IDs
    without the ".desktop" extension. Those are then sorted:
    
    >>> GLib.strcmp0("gnome-xorg", "gnome")
    45
    
    which gives a different ordering.
    
    Fix this bug by calculating the fallback session in the same way, by
    removing ".desktop" from the filename.
    
    https://bugs.launchpad.net/ubuntu/+source/gnome-session/+bug/1705157
    
    https://bugzilla.gnome.org/show_bug.cgi?id=787304

 daemon/gdm-session.c |   17 +++++------------
 1 files changed, 5 insertions(+), 12 deletions(-)
---
diff --git a/daemon/gdm-session.c b/daemon/gdm-session.c
index 0b83223..063c5a2 100644
--- a/daemon/gdm-session.c
+++ b/daemon/gdm-session.c
@@ -573,8 +573,8 @@ get_fallback_session_name (GdmSession *self)
                         }
 
                         if (get_session_command_for_file (self, base_name, NULL)) {
-
-                                g_sequence_insert_sorted (sessions, g_strdup (base_name), (GCompareDataFunc) 
g_strcmp0, NULL);
+                                name = g_strndup (base_name, strlen (base_name) - strlen (".desktop"));
+                                g_sequence_insert_sorted (sessions, name, (GCompareDataFunc) g_strcmp0, 
NULL);
                         }
                 } while (base_name != NULL);
 
@@ -589,22 +589,15 @@ get_fallback_session_name (GdmSession *self)
                 g_error ("GdmSession: no session desktop files installed, aborting...");
 
         do {
-               if (g_sequence_get (session)) {
-                       char *base_name;
-
-                       g_free (name);
-                       base_name = g_sequence_get (session);
-                       name = g_strndup (base_name,
-                                         strlen (base_name) -
-                                         strlen (".desktop"));
-
+               name = g_sequence_get (session);
+               if (name) {
                        break;
                }
                session = g_sequence_iter_next (session);
         } while (!g_sequence_iter_is_end (session));
 
         g_free (self->priv->fallback_session_name);
-        self->priv->fallback_session_name = name;
+        self->priv->fallback_session_name = g_strdup (name);
 
         g_sequence_free (sessions);