[mousetweaks] Use xdg runtime dir for pid file. Fixes bgo #675447.

[Gerd Kohlberger <gerdk src gnome org>]

commit db94513c10c2ca307a0e66464271f87b00ddd312
Author: Gerd Kohlberger <gerdk src gnome org>
Date:   Thu May 10 15:24:05 2012 +0200

    Use xdg runtime dir for pid file. Fixes bgo #675447.

 man/mousetweaks.1 |    7 ++++---
 src/mt-pidfile.c  |   11 ++++++++++-
 2 files changed, 14 insertions(+), 4 deletions(-)
---
diff --git a/man/mousetweaks.1 b/man/mousetweaks.1
index 96914d4..32a1125 100644
--- a/man/mousetweaks.1
+++ b/man/mousetweaks.1
@@ -57,10 +57,11 @@ Start mousetweaks in the background, ie. spawn a child process.
 Start mousetweaks in login mode. Login mode enables workarounds specific
 to GDM. Currently unused.
 .SH FILES
-.I ~/.mousetweaks.pid
+.I mousetweaks.pid
 .RS
-The daemon creates a lock file in the users home directory to keep track
-of its status.
+The daemon creates a lock file in the $XDG_RUNTIME_DIR directory to keep track
+of its state. On systems with no user runtime directory, the $XDG_CACHE_HOME
+directory is used.
 .SH BUGS
 Report bugs to
 .UR http://bugzilla.gnome.org/
diff --git a/src/mt-pidfile.c b/src/mt-pidfile.c
index cac3180..d02170a 100644
--- a/src/mt-pidfile.c
+++ b/src/mt-pidfile.c
@@ -48,8 +48,17 @@ static const char *
 mt_pidfile_proc (void)
 {
     static char fn[512];
+    static int  fn_set = 0;
+
+    if (!fn_set)
+    {
+        snprintf (fn, sizeof (fn),
+                  "%s%smousetweaks.pid",
+                  g_get_user_runtime_dir (),
+                  G_DIR_SEPARATOR_S);
+        fn_set = 1;
+    }
 
-    snprintf (fn, sizeof (fn), "%s/.mousetweaks.pid", g_get_home_dir ());
     return fn;
 }