xrootdatetime: force update on SIGUSR1

modules/dwm.nix

@@ -50,7 +50,7 @@ in
           xsetroot = getExe pkgs.xorg.xsetroot;
         in
           /* bash */ ''
-          while true; do
+          function update_x_root() {
             set +e # allow errors
             mute="$(${pamixer} --default-source --get-mute)"
             set -e # disallow errors
@@ -63,7 +63,14 @@ in
 
             dateTime=$(date +"<-- %A, %B %d -- %H:%M -->")
             ${xsetroot} -name "$mutedString$dateTime"
-            sleep 1
+          }
+
+          trap update_x_root SIGUSR1
+
+          while true; do
+            sleep 1 &
+            wait
+            update_x_root
           done
         '';
       wantedBy = [ "graphical-session.target" ];