Android platform

[i509VCB]

EDIT: A bit of discussion on this happened in rust-windowing/swbuf#8 (comment)

[MarijnS95]

The most likely way to implement this would be via ANativeWindow_lock(), whose API has been wrapped for the ndk crate at:

https://github.com/MarijnS95/ndk/compare/window-lock

We can merge this into the ndk crate after some slight cleanup.

[ids1024]

Using ANativeWindow_lock, is there a way to request that the window uses an BGRX buffer like SoftBuffer currently assumes? Or would we have to deal with a different pixel format? (And if that could vary, things become even more complicated...)

[MarijnS95]

@ids1024 There is a way to change the format, see how the example has a (commented out) way to do this:

rust-mobile/ndk@master...MarijnS95:ndk:window-lock#diff-f302a34380ff35caef13c0c344aede7c4c0bf4ae4b957e066ad0bc73eb4cc418R10

Unfortunately there's no support for BGRX, only RGBX:

https://docs.rs/ndk/latest/ndk/hardware_buffer_format/enum.HardwareBufferFormat.html
https://developer.android.com/reference/android/hardware/HardwareBuffer

[ids1024]

Right. Hopefully we can at least expect RGBX to always work?

In comparison Wayland's wl_shm has a huge list of formats but only requires a compositor to support argb8888 and xrgb8888 (which a little endian, so the same as formats called BGRA/BGRX elsewhere).

It seems we can't expect to use the same pixel format everywhere while also getting performant no-copy presentation.