bug#39491: 28.0.50; two bugs in battery-upower

[Richard Stallman]

battery-upower crashes on my laptop because there is no BatteryLevel property.
This code

          (cons ?b (cond ((= level 3) "-")
                         ((= level 4) "!")
                         (online-p "+")
                         (t "")))

needs to handle nil.  I don't know what value it should return for that case.

However, that function has a design flaw: it reports on just the first
battery in the list.  battery-upower-device-list correctly returns a
list with an element for each battery, but battery-upower finds only one
of them (the first one in the list) and ignores the others.

The old code handle all the batteries and added the energy quantities
so as to report accurately the total power available and overall
fraction of charge.  I wrote that code myself, around 10 years ago.

Please restore the lost functionality.



In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 2.24.30, cairo 
version 1.14.6)
 of 2020-02-06 built on softly
Repository revision: c4be80112556e06bd7e92138e44051cc8c62e709
Repository branch: master
System Description: Trisquel GNU/Linux Flidas (8.0)

Recent messages:
(("NativePath" . "BAT0") ("Vendor" . "SANYO") ("Model" . "42T4832") ("Serial" . 
"19849") ("UpdateTime" . 1581079789) ("Type" . 2) ("PowerSupply" . t) 
("HasHistory" . t) ("HasStatistics" . t) ("Online") ("Energy" . 35.21) 
("EnergyEmpty" . 0.0) ("EnergyFull" . 35.21) ("EnergyFullDesign" . 43.29) 
("EnergyRate" . 2.237) ("Voltage" . 12.504) ("Luminosity" . 0.0) ("TimeToEmpty" 
. 0) ("TimeToFull" . 0) ("Percentage" . 100.0) ("Temperature" . 0.0) 
("IsPresent" . t) ("State" . 4) ("IsRechargeable" . t) ("Capacity" . 
81.33518133518135) ("Technology" . 1) ("WarningLevel" . 1) ("IconName" . 
"battery-full-charged-symbolic"))
Back to top level
battery-upower
Saving file /home/rms/emacs-git/build-feb-6/lisp/battery.el...
Wrote /home/rms/emacs-git/build-feb-6/lisp/battery.el
Quit
Power on-line, battery fully-charged (100% load, remaining time 0:00)
Mark set [2 times]
(("line_power_AC" . :line-power) ("battery_BAT0" . :battery) ("battery_BAT1" . 
:battery))
completing-read-default: Command attempted to use minibuffer while in minibuffer
Quit
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-- 
Dr Richard Stallman
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)