[evolution] Delay saving Evolution version until later in initialization.

[Matthew Barnes <mbarnes src gnome org>]

commit a0957f73f6dace58be61edc5e01f0ec0d27be90f
Author: Matthew Barnes <mbarnes redhat com>
Date:   Mon Jul 2 18:42:16 2012 -0400

    Delay saving Evolution version until later in initialization.
    
    Save the version after the startup wizard has had a chance to
    run.  If the user chooses to restore data and settings from a
    backup, Evolution will restart and the restored data may need
    to be migrated.
    
    If we save the version before the restart, then Evolution will
    think it has already migrated data and settings to the current
    version and the restored data may not be handled properly.

 shell/e-shell-migrate.c |   82 +++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 68 insertions(+), 14 deletions(-)
---
diff --git a/shell/e-shell-migrate.c b/shell/e-shell-migrate.c
index 26901e7..6ebc585 100644
--- a/shell/e-shell-migrate.c
+++ b/shell/e-shell-migrate.c
@@ -753,6 +753,29 @@ shell_migrate_get_version (EShell *shell,
 	g_object_unref (settings);
 }
 
+static gboolean
+shell_migrate_downgraded (gint previous_major,
+                          gint previous_minor,
+                          gint previous_micro)
+{
+	gboolean downgraded;
+
+	/* This could just be a single boolean expression,
+	 * but I find this form easier to understand. */
+
+	if (previous_major == EVO_MAJOR_VERSION) {
+		if (previous_minor == EVO_MINOR_VERSION) {
+			downgraded = (previous_micro > EVO_MICRO_VERSION);
+		} else {
+			downgraded = (previous_minor > EVO_MINOR_VERSION);
+		}
+	} else {
+		downgraded = (previous_major > EVO_MAJOR_VERSION);
+	}
+
+	return downgraded;
+}
+
 static void
 change_dir_modes (const gchar *path)
 {
@@ -794,20 +817,57 @@ fix_folder_permissions (const gchar *data_dir)
 		change_dir_modes (data_dir);
 }
 
+static void
+shell_migrate_save_current_version (void)
+{
+	GSettings *settings;
+	gchar *version;
+
+	/* Save the version after the startup wizard has had a chance to
+	 * run.  If the user chooses to restore data and settings from a
+	 * backup, Evolution will restart and the restored data may need
+	 * to be migrated.
+	 *
+	 * If we save the version before the restart, then Evolution will
+	 * think it has already migrated data and settings to the current
+	 * version and the restored data may not be handled properly.
+	 *
+	 * This implies an awareness of module behavior from within the
+	 * application core, but practical considerations overrule here. */
+
+	settings = g_settings_new ("org.gnome.evolution");
+
+	version = g_strdup_printf (
+		"%d.%d.%d",
+		EVO_MAJOR_VERSION,
+		EVO_MINOR_VERSION,
+		EVO_MICRO_VERSION);
+	g_settings_set_string (settings, "version", version);
+	g_free (version);
+
+	g_object_unref (settings);
+}
+
+static void
+shell_migrate_ready_to_start_event_cb (EShell *shell)
+{
+	shell_migrate_save_current_version ();
+}
+
 gboolean
 e_shell_migrate_attempt (EShell *shell)
 {
 	ESEvent *ese;
-	GSettings *settings;
 	gint major, minor, micro;
-	gchar *string;
 
 	g_return_val_if_fail (E_IS_SHELL (shell), FALSE);
 
-	settings = g_settings_new ("org.gnome.evolution");
-
 	shell_migrate_get_version (shell, &major, &minor, &micro);
 
+	/* Abort all migration if the user downgraded. */
+	if (shell_migrate_downgraded (major, minor, micro))
+		return TRUE;
+
 	/* Migrate to XDG Base Directories first, so shell backends
 	 * don't have to deal with legacy data and cache directories. */
 	shell_migrate_to_xdg_base_dirs (shell);
@@ -821,16 +881,10 @@ e_shell_migrate_attempt (EShell *shell)
 	if (!shell_migrate_attempt (shell, major, minor, micro))
 		_exit (EXIT_SUCCESS);
 
-	/* Record a successful migration. */
-	string = g_strdup_printf (
-		"%d.%d.%d",
-		EVO_MAJOR_VERSION,
-		EVO_MINOR_VERSION,
-		EVO_MICRO_VERSION);
-	g_settings_set_string (settings, "version", string);
-	g_free (string);
-
-	g_object_unref (settings);
+	/* We want our handler to run last, hence g_signal_connect_after(). */
+	g_signal_connect_after (
+		shell, "event::ready-to-start",
+		G_CALLBACK (shell_migrate_ready_to_start_event_cb), NULL);
 
 	/** @Event: Shell attempted upgrade
 	 * @Id: upgrade.done