ZeroCopy.txt

https://bugs.chromium.org/p/chromium/issues/detail?id=322780

Determine if GL_TEXTURE_EXTERNAL_OES can be used as texture target for zero-copy on Android	

Status:	Fixed
Owner:	reve...@chromium.org
Closed:	Mar 2014
Components:	
Internals>GPU
OS:	Android
Type:	Bug

The compositor can use GL_TEXTURE_RECTANGLE_ARB or
GL_TEXTURE_EXTERNAL_OES target for zero-copy texture bindings. We
should verify that this works and performs properly before we enable
it on Android.

Webview for now but will also effect Chrome if we implement zero-copy
support using SurfaceTexture.

UsingMapImage and SurfaceTexture

https://docs.google.com/document/d/1J0fkaGS9Gseczw3wJNXvo_r-O5-SZmTlDvbgn56pdQI/edit

I haven't had a chance to read the doc in #5 yet, but to summarize how
it could be used for zero copy:

It would involve using 'single-buffer' mode on SurfaceTexture (KitKat
only), and using the ANativeWindow_lock/ANativeWindow_unlockAndPost
native APIs to upload data across processes. SurfaceTextures can
either be used as staging transfer buffers (with a GPU copy into a
normal texture when they arrive in the GPU process), or they could be
used as textures themselves. The latter is fairly difficult due to
synchronization issues imposed by Android's SurfaceTexture API, but it
might still be possible, and this would eliminate the GPU copy in the
staging approach.