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Bug 2170 - Implement SDL_GetPowerInfo() on Linux using UPower
Summary: Implement SDL_GetPowerInfo() on Linux using UPower
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: main (show other bugs)
Version: HG 2.1
Hardware: x86_64 Linux
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-10-21 15:45 UTC by Bastien Nocera
Modified: 2017-08-15 05:17 UTC (History)
2 users (show)

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Description Bastien Nocera 2013-10-21 15:45:50 UTC 
On Linux, OpenBSD and FreeBSD, one can use D-Bus to query the state of batteries.

UPower 1.0, slated for release in 2014 along with GNOME 3.12, introduces a "display" battery that aggregates all the batteries and power state.

This is the output of a command-line call that displays the battery info:
$ gdbus call --system --dest org.freedesktop.UPower --object-path /org/freedesktop/UPower/devices/DisplayDevice --method org.freedesktop.DBus.Properties.GetAll 'org.freedesktop.UPower.Device'

({'NativePath': <''>, 'Vendor': <''>, 'Model': <''>, 'Serial': <''>, 'UpdateTime': <uint64 0>, 'Type': <uint32 2>, 'PowerSupply': <true>, 'HasHistory': <false>, 'HasStatistics': <false>, 'Online': <false>, 'Energy': <44.670000000000002>, 'EnergyEmpty': <0.0>, 'EnergyFull': <44.670000000000002>, 'EnergyFullDesign': <0.0>, 'EnergyRate': <10.019>, 'Voltage': <0.0>, 'Luminosity': <0.0>, 'TimeToEmpty': <int64 16050>, 'TimeToFull': <int64 0>, 'Percentage': <100.0>, 'Temperature': <0.0>, 'IsPresent': <true>, 'State': <uint32 2>, 'IsRechargeable': <false>, 'Capacity': <0.0>, 'Technology': <uint32 0>, 'WarningLevel': <uint32 1>, 'IconName': <'battery-full-symbolic'>},)

And you can see that it makes it easy to implement returning the time-to-empty, the percentage of battery left, and even the state, even if there are multiple batteries.

I haven't implemented it, as it would be quite a bit of code, and I'm wondering whether it's useful to games and other applications before implementing it.
Comment 1 Ryan C. Gordon 2015-06-03 20:13:32 UTC 
I just implemented an updated SDL_GetPowerInfo() that parses the sysfs entries (which is basically what UPower does, I assume), which we would need anyhow for embedded systems that don't offer D-Bus, but I think talking to UPower is the preferred way to do this, so we should implement this at some point and keep the sysfs implementation as a fallback.

The sysfs stuff is here: https://hg.libsdl.org/SDL/rev/d8cc85e50561

I'll take this bug for now, but I won't be hooking up to UPower before SDL 2.0.4 ships.

--ryan.
Comment 2 Sam Lantinga 2017-08-15 05:17:31 UTC 
Ryan implemented this here:
https://hg.libsdl.org/SDL/rev/5be3faa49e54