Prefer more standard names for battery icons

[newhoa]

Problem

mate-power-manager still seems to use the old gnome-power-manager gpm- prefixed names for battery icons. Also, the tray and the power statistics window each prefer different sets of icons (see the bottom of this post for details). These are not used for any other desktops and are not provided in many modern icon themes. They are probably less likely to be provided as time goes on since other desktop environments are using the same naming standard.

Other Desktop Environments

Gnome, Xfce, and Cinnamon use a new icon naming standard. battery-level-##-symbolic for more granular icons in places like panels and trays. And as an example used for less granular places, battery-caution -- this style is the Upower standard and is currently the most common in icon themes.

Granular naming adopted by other desktops (there is no non-symbolic variation):

battery-level-0-charging-symbolic
battery-level-0-symbolic
battery-level-10-charging-symbolic
battery-level-10-symbolic
battery-level-20-charging-symbolic
battery-level-20-symbolic
battery-level-30-charging-symbolic
battery-level-30-symbolic
battery-level-40-charging-symbolic
battery-level-40-symbolic
battery-level-50-charging-symbolic
battery-level-50-symbolic
battery-level-60-charging-symbolic
battery-level-60-symbolic
battery-level-70-charging-symbolic
battery-level-70-symbolic
battery-level-80-charging-symbolic
battery-level-80-symbolic
battery-level-90-charging-symbolic
battery-level-90-symbolic
battery-level-100-charged-symbolic
battery-level-100-symbolic

Upower names -- all of these are also used with the -symbolic suffix:

ac-adapter
battery-missing
battery-empty
battery-empty-charging
battery-caution
battery-caution-charging
battery-low
battery-low-charging
battery-good
battery-good-charging
battery-full
battery-full-charged
battery-full-charging

Solution

For the tray/panel icon, I think preferring the battery-level- names first and falling back to the Upower symbolic names would be the best solution.

For power statistics if symbolic icons are not preferred, prefer Upower non-symbolic first, then fall back to the other two symbolic names.

And then if needed the gpm- icons as a lowest-priority fallback.