[WIP] External display support on Android

[imxieyi]

Just like iOS (#12094), Android also supports external displays (via Miracast, HDMI, etc.). As mentioned by @unknownbrackets, this gives more reason to separate virtual gamepad from game view. I don't have a decent Android device to test. It currently works with virtual display in Android Emulator:

This utilizes Presentation API. There are several similarities about external display support on iOS and Android:

• Each display has its own root Context(Android) or UIViewController(iOS).
• Just like GLKView on iOS, SurfaceView on Android can be easily moved from one display to another.
• A listener can be setup to monitor display plugging and unplugging.

[Florin9doi]

The menus should also remain on the primary display, together with the virtual gamepad. Otherwise, there wont be any way to use them. Just the game view can be moved to a secondary display.

[WeedyWeedSmoker]

@Florin9doi I think the menus should be on the external screen : if you play on a TV, you probably use a joystick for that purpose — and navigating the menus directly with the joystick is easier if they show up on the big screen...

[Florin9doi]

@WeedyWeedSmoker, what you ask for is the way how it already works right now.

[WeedyWeedSmoker]

@Florin9doi Yeah, just voicing some opinion over here... 😄 I've seen cases where the changes have been implemented by request, where the "old" behavior was in fact better for some people... Wouldn't mind if that was an option though ! (Maybe only after actually implementing the virtual gamepad)

[unknownbrackets]

The way I see it, the ideal thing would be to show menus on both. That might be harder, but I'm thinking:

• Virtual controls only on device.
• Game only on display (or potentially on both, but this might have worse performance, so at least an option...)
• Menus on both display and device.
• FPS and debug menus only on device? Optionally both?
• On-screen messages only on display or both.

I wonder how the GL here actually works. The Android docs seem pretty light here - unclear if it's a separate GL context or separate threads or what.

-[Unknown]