slave: kill off clients from display when finished

When we're done with the display we need to kill off any clients
that are lingering and close our own connection to the display.

This is so, for instance, processes from the session don't
stick around on a -noreset Xvnc server (or something)

https://bugzilla.gnome.org/show_bug.cgi?id=776059

1 files changed, 29 insertions, 0 deletions

diff --git a/daemon/gdm-display.c b/daemon/gdm-display.c
index 4b035d6f..0057e2ce 100644
--- a/daemon/gdm-display.c
+++ b/daemon/gdm-display.c
@@ -648,6 +648,35 @@ gdm_display_finish (GdmDisplay *self)
 static void
 gdm_display_disconnect (GdmDisplay *self)
 {
+        /* These 3 bits are reserved/unused by the X protocol */
+        guint32 unused_bits = 0b11100000000000000000000000000000;
+        XID highest_client, client;
+        guint32 client_increment;
+        const xcb_setup_t *setup;
+
+        if (self->priv->xcb_connection == NULL) {
+                return;
+        }
+
+        setup = xcb_get_setup (self->priv->xcb_connection);
+
+        /* resource_id_mask is the bits given to each client for
+         * addressing resources */
+        highest_client = (XID) ~unused_bits & ~setup->resource_id_mask;
+        client_increment = setup->resource_id_mask + 1;
+
+        /* Kill every client but ourselves, then close our own connection
+         */
+        for (client = 0;
+             client <= highest_client;
+             client += client_increment) {
+
+                if (client != setup->resource_id_base)
+                        xcb_kill_client (self->priv->xcb_connection, client);
+        }
+
+        xcb_flush (self->priv->xcb_connection);
+
         g_clear_pointer (&self->priv->xcb_connection, xcb_disconnect);
 }