bug#41540: Implement %b status to battery-linux-sysfs in emacs 26.3

[Ellington Santos]

This patch implements %b battery status to battery-linux-sysfs in 
emacs-26.3 battery.el

diff --git a/lisp/battery.el b/lisp/battery.el
index e23dab4c91..1d5969762f 100644
--- a/lisp/battery.el
+++ b/lisp/battery.el
@@ -433,13 +433,15 @@ 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
@@ -509,6 +511,8 @@ 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 (format "%.1f" (/ (* 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")))
@@ -522,10 +526,11 @@ 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 (or percentage-now "N/A"))
          (cons ?L (cond
                     ((battery-search-for-one-match-in-files
                       (list "/sys/class/power_supply/AC/online"


--

Atenciosamente,

Ellington Santos