Improve battery status display via GNU/Linux sysfs

* lisp/battery.el (battery-linux-sysfs): Support %b format.
Improve the display of %p.  (Bug#41542)

Copyright-paperwork-exempt: yes

1 files changed, 12 insertions, 5 deletions

diff --git a/lisp/battery.el b/lisp/battery.el
index 7027b254480..b8855a8ce37 100644
--- a/lisp/battery.el
+++ b/lisp/battery.el
@@ -441,13 +441,15 @@ The following %-sequences are provided:
 %c Current capacity (mAh or mWh)
 %r Current rate
 %B Battery status (verbose)
+%b Battery status, empty means high, `-' means low,
+   `!' means critical, and `+' means charging
 %d Temperature (in degrees Celsius)
 %p Battery load percentage
 %L AC line status (verbose)
 %m Remaining time (to charge or discharge) in minutes
 %h Remaining time (to charge or discharge) in hours
 %t Remaining time (to charge or discharge) in the form `h:min'"
-  (let (charging-state temperature hours
+  (let (charging-state temperature hours percentage-now
         ;; Some batteries report charges and current, other energy and power.
         ;; In order to reliably be able to combine those data, we convert them
         ;; all to energy/power (since we can't combine different charges if
@@ -515,6 +517,8 @@ The following %-sequences are provided:
                                  energy-now
                                (- energy-full energy-now))))
               (setq hours (/ remaining power-now)))))))
+    (when (and (> energy-full 0) (> energy-now 0))
+      (setq percentage-now (/ (* 100 energy-now) energy-full)))
     (list (cons ?c (cond ((or (> energy-full 0) (> energy-now 0))
                           (number-to-string (/ energy-now voltage-now)))
                          (t "N/A")))
@@ -528,10 +532,13 @@ The following %-sequences are provided:
                      "N/A"))
           (cons ?d (or temperature "N/A"))
           (cons ?B (or charging-state "N/A"))
-          (cons ?p (cond ((and (> energy-full 0) (> energy-now 0))
-                          (format "%.1f"
-                                  (/ (* 100 energy-now) energy-full)))
-                         (t "N/A")))
+          (cons ?b (or (and (string= charging-state "Charging") "+")
+                       (and percentage-now (< percentage-now battery-load-critical) "!")
+                       (and percentage-now (< percentage-now battery-load-low) "-")
+                       ""))
+          (cons ?p (cond
+                    ((and percentage-now (format "%.1f" percentage-now)))
+                    (t "N/A")))
           (cons ?L (cond
                     ((battery-search-for-one-match-in-files
                       (list "/sys/class/power_supply/AC/online"