Support functions for gl in golang.org/x/mobile/

[Sri Gogineni]

Hi Gophers,

I'm pretty excited about writing Android apps in Go, especially with the ability to leverage OpenGL ES! 

While working on the Android graphics tutorials, I noticed some functions which greatly ease development like Matrix manipulations (e.g. android.opengl.Matrix.*) and camera perspective helper functions (OpenGL GLUT documentation for gluLookAt) are not readily available, to my knowledge, in Go. Where would be the appropriate place to add these functions?

[David Crawshaw]

There's a lot of useful tools in http://github.com/go-gl, some of
which is compatible with Android. Check out the mathgl package.

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[Sri Gogineni]

Thanks David! I'll take a deeper look at those libraries.

I'm also playing around with EGL on Android 4.4. With the current toolchain, I was able to access EGL functionality by adding:

/*
#include <EGL/egl.h>
#include <EGL/eglplatform.h>
#cgo LDFLAGS: -lEGL
*/
import "C"

and an example function:

/*
  eglQueryString(eglGetCurrentDisplay(), EGLint)

  VENDOR      = 0x3053
  VERSION     = 0x3054
  EXTENSIONS  = 0x3055
  CLIENT_APIS = 0x308D
*/
func eglGetQueryString(name int32) string {
  return C.GoString(C.eglQueryString(C.eglGetCurrentDisplay(), C.EGLint(name)))
}

Although this works, it doesn't seem idiomatic at all. Will EGL be included in /x/mobile/egl ?

[Nigel Tao]

On Mon, May 11, 2015 at 7:09 AM, Sri Gogineni
<sriakhil...@gmail.com> wrote:
> Will EGL be included in /x/mobile/egl ?

crawshaw is the person to ask, but he's on vacation right now.

My guess is that the answer is no, and that we're aiming to offer
something a lot more focused than wrapping the entirety of all the
numerous *GL* C APIs.

[Sri Gogineni]

Go coverage of the EGL API allows for obtaining a native window/surface without having to call out to EGL C code. This increases portability and allows for a complete OpenGL ES application to be built entirely in Go.

[David Crawshaw]

EGL only works on Android. A goal of the x/mobile packages is to be
portable across different mobile devices, so the x/mobile/app package
uses EGL on Android but does not expose it directly.

I think there is a place for a good Go EGL binding, but I don't think
it's in the x/mobile repository.

[Anthony Starks]

What is your opinion on devices like the Raspberry Pi, which includes EGL?

Should x/mobile support these kind of devices which tend to have mobile-style GPUs and libraries?

[David Crawshaw]

My only use of a Raspberry Pi was early in its life, running a
headless debian install, so I'm sure EGL wouldn't work there. If there
is a standard Raspberry Pi distribution today that by default uses
EGL, I think it would be reasonable to make the x/mobile/app package
run on it.

Though I do not yet have the mobile sub-repository running
continuously on build.golang.org, which makes it hard to even keep our
current environments building. I would like to see x/mobile trybots
for OS X, linux/x11, android, and iOS before adding more build
configurations.

[Anthony Starks]

On Friday, June 19, 2015 at 11:29:08 AM UTC-4, David Crawshaw wrote:

My only use of a Raspberry Pi was early in its life, running a
headless debian install, so I'm sure EGL wouldn't work there. If there
is a standard Raspberry Pi distribution today that by default uses
EGL, I think it would be reasonable to make the x/mobile/app package
run on it.

That's good news.  FYI, https://github.com/ajstarks/openvg has a Go wrapper for OpenVG which uses a bit of EGL