Add battery widget to mowedline

mowedline/.config/mowedline/init.org

@@ -121,6 +121,48 @@ Define a convenience function to add a Font Awesome icon to a widget.
        #:format (compose text-maybe-pad-left (add-fa-icon ""))))
   #+END_SRC
 
+* Battery
+
+  I'm on a laptop and seeing the state of my battery is pretty important.
+
+  #+BEGIN_SRC scheme
+    (define (clamp x low high)
+      (max low (min high x)))
+
+    (define (source:sys)
+      (list
+       (/ (clamp (with-input-from-file
+                     "/sys/class/power_supply/BAT0/capacity"
+                   read)
+                 0 100)
+          100.0)
+       (with-input-from-file
+           "/sys/class/power_supply/BAT0/status"
+         read)))
+
+    (define (widget:battery)
+      (widget:text
+       font: "FontAwesome-10"
+       format:
+       (compose
+        text-maybe-pad-left
+        (match-lambda
+         ((capacity status)
+          (list
+           (list-ref
+            '((color "#a85454" "")
+              (color "#a88654" "")
+              (color "#8d995c" "")
+              (color "#65a854" "")
+              (color "#5476a8" ""))
+            (inexact->exact
+             (round (* 4 capacity))))
+           (if (eq? 'Charging status) " " "")))
+         (val val)))
+       init: (lambda (widget)
+               (widget-update-at-interval widget 5 source:sys))))
+  #+END_SRC
+
 * The window
 
   Create a mowedline window, put it at the bottom.
@@ -154,5 +196,6 @@ Define a convenience function to add a Font Awesome icon to a widget.
             clipboard-widget
             (widget:text #:name "irc" #:format (lambda (text) (text-maybe-pad-left (with-input-from-string text read))))
             email-widget
+            (widget:battery)
             (widget:clock #:format text-maybe-pad-left))
   #+END_SRC