implement wakelock for sdl2

[brentpicasso]

resolves #1061.

Not sure if this is the best implementation, but seems to work based on my limited testing.

[brentpicasso]

Note, I tried to implement the approach in the pygame implementation, but I didn't get the initial onResume() when the app first fired up. So, I acquired the lock immediately if the flag was set; seemed like there was no reason for it to not work that way.

The pygame implementation seemed cleaner with only one acquire and one release present, however.

Feedback appreciated; interested in getting this merged ASAP as my app needs wakelock. :)

[inclement]

Thanks for the PR, it looks okay but I haven't had time to test it yet.

There's actually an alternative way to do this with SDL2, which in Kivy you can access with from kivy.core.window import Window and Window.allow_screensaver = False. I think this uses FLAG_KEEP_SCREEN_ON rather than a wakelock.

[brentpicasso]

thanks for checking it out. Happy to continue using the official mechanism if it's not being deprecated.

[inclement]

Seems good, thanks.

[ghost]

Not this.mWakeLock.isHeld()?