From 5af2a76b43a9fd48764988e515f36e62932018c9 Mon Sep 17 00:00:00 2001
From: Timo Wilken
Date: Sun, 22 Jan 2023 22:16:21 +0100
Subject: Only start polybar if its monitor is connected

---
 tw/home/lap.scm | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

(limited to 'tw')

diff --git a/tw/home/lap.scm b/tw/home/lap.scm
index becb74e5..20e23f0c 100644
--- a/tw/home/lap.scm
+++ b/tw/home/lap.scm
@@ -67,12 +67,33 @@
        (".local/bin/mutt_oauth2.py"
         ,(local-file "files/neomutt/contrib/oauth2/mutt_oauth2.py" #:recursive? #t))))))
 
+(define polybar-wrapper
+  (program-file
+   "polybar-wrapper"
+   #~(begin
+       ;; This wrapper program checks that the monitor we want to start
+       ;; polybar on is actually connected.
+       (use-modules (ice-9 popen)
+                    (ice-9 rdelim))
+       (let* ((connected-str (string-append (getenv "POLYBAR_MONITOR") " connected"))
+              (xrandr (open-pipe* OPEN_READ #$(file-append xrandr "/bin/xrandr") "-q"))
+              (monitor-connected?
+               (let loop ((line (read-line xrandr)))
+                 (cond
+                  ((eof-object? line) #f)                   ; we didn't find our monitor connected
+                  ((string-prefix? connected-str line) #t)  ; the monitor we want is connected
+                  (else (loop (read-line xrandr)))))))      ; keep looking
+         (close-pipe xrandr)
+         (when monitor-connected?
+           (execl #$(file-append polybar "/bin/polybar")))))))
+
 (define (polybar-service monitor)
   (shepherd-service
    (documentation (string-append "Polybar desktop bar for monitor " monitor "."))
    (provision (list (string->symbol (string-append "polybar-" monitor))))
+   (requirement '(xorg-setup))
    (start #~(make-forkexec-constructor
-             (list #$(file-append polybar "/bin/polybar"))
+             (list #$polybar-wrapper)
              #:environment-variables
              (cons #$(string-append "POLYBAR_MONITOR=" monitor)
                    (default-environment-variables))))
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