[mpv] Add auto configuration low power mode

Add low power profile auto-setting if, on opening mpv, the battery mode
is detected. This will not automatically change when laptop is beginning
to charge/discharge *during* mpv being open.

mpv/.config/mpv/scripts/battery.lua

@@ -0,0 +1,17 @@
+-- If the laptop is on battery, the profile 'lq' will be loaded; otherwise 'hq' is used
+local lqprofile = "lq"
+local hqprofile = "hq"
+local utils = require 'mp.utils'
+if mp.get_property_bool("option-info/vo/set-from-commandline") == true then
+    return
+end
+t = {}
+t.args = {"/bin/cat", "/sys/class/power_supply/AC/online"}
+res = utils.subprocess(t)
+if res.stdout == "0\n" then
+    mp.msg.info("On Battery, setting low-quality options.")
+    mp.set_property("profile", lqprofile)
+    mp.set_property("speed", 2)
+else
+    mp.msg.info("On AC, setting high-quality options.")
+end