Ghostty Android renderer port

[IlyaGulya]

Hi!

I've ported and tested Ghostty's Linux renderer for Android (OpenGL ES 3.1) for use in my application, and I'd be interested in contributing it upstream.

I tried to keep the implementation consistent with the existing rendering backends, with Ghostty fully owning rendering and the host application not participating in the rendering process.

Before opening a PR, I wanted to ask what your expectations would be for something like this. In particular:

• What would you want to see for the PR to be considered for acceptance?
• Would Android integration / end-to-end testing on an emulator be expected as part of the PR?
• Are there any other tests or requirements I should plan for?

If you'd prefer, I'm also happy to open a draft PR first so we can discuss the approach there.

Separately, I've also implemented an external_io backend instead of exec, which allows the host application to provide terminal data directly. If that sounds useful, I'd be glad to submit a PR for that as well.

[pandalec]

For Halium Linux Mobile Devices this would be also awesome. I couldn't get Ghostty work on FuriOS due to OpenGL ES. Could you spin up a fork somewhere? I'd love to test this.

[rhodes-b]

Andriod is likely much more suited for a libghostybased application instead of mainstream ghostty, or keeping it as a fork works too
this is the stance that has been taken for other mobile targets like ios and ipad.

[pluiedev]

GLES would be interesting as a way to support devices with lower-end hardware, but we aren't interested in porting Ghostty (the app) to work on Android. If you can condense your changes into just the GLES renderer we might take a look at it.

[mattkanwisher]

related I did a patch for opengl es3.1 and Vulcan for the raspberry pi, in theory should unlock android same way #13907