The battery popout already surfaces the UPower energy rate, but the bar
widget could only show percentage and remaining time, so telling how fast
the battery is charging or draining meant opening the popout (or running a
third-party plugin that polls /sys/class/power_supply).
Add two independent, opt-in toggles to the battery widget - "Show Charge
Rate" and "Show Discharge Rate" - that render the signed rate next to the
existing text, e.g. "+28W" while charging and "77% (2h 11m) -19W" while
draining. Both default to off, and follow the established pattern: a global
default in SettingsData plus a per-widget-instance override.
The value comes from BatteryService.changeRate, so there is no extra process
or polling. It hides itself when the rate is below 0.05W (idle, fully
charged, or sitting at a charge limit) so it costs no bar space unless it
has something to say. Precision adapts to keep the pill narrow: one decimal
below 10W, whole watts above; vertical bars get a whole-watt line.
Spyros Psarras
212271291c