[Mesa-dev] GL_TEXTURE_2D to wl_buffer

[Jason Ekstrand]

On Sat, Mar 28, 2015 at 6:57 AM, x414e54 <x414e54 at linux.com> wrote:
> I am attempting to pass a GL_TEXTURE_2D directly to a Wayland compositor
by
> first converting it so an EGLImageKHR and then to a wl_buffer.
>
> eglCreateImageKHR appears to work fine but when calling
> glCreateWaylandBufferFromImageWL I get EGL_BAD_MATCH "unsupported image
> format".
>
> The GL_TEXTURE_2D is in GL_RGBA format.
>
> Is this going to be possible or should I look for an alternative way?

I wouldn't expect this to work at all in general. The
glCreateWaylandBufferFromImageWL extension was initially created for nested
compositor. The intention was to take buffers recieved by a nested
compositor from Wayland client and then hand them directly off to the
parent compositor. In other words, the buffers were something that already
came from a Wayland client and so handing them off across the Wayland
protocol was always safe. This was never intended for passing around
arbitrary EGLImages.

Why not? There may be all sorts of tiling, stride, and color format
restrictions required by the compositor half of the graphics stack that may
not be required for a texture. For instance, if you want to be able to scan
out from the buffer directly, the restrictions are usually fairly heavy.

How can you do this?  One way would be to use GBM to allocate your buffer
and then import it into egl to render and then talk the wl_drm protocol
directly.  However, this is far more complicated than you probably want
and, while it will work with mesa, it is not a general solution.

If you gave a more high-level description of what you are trying to do, I
may be able to help better.  It's quite possible that there is a fairly
simple way to do it.

> I was originally blitting the texture to the default framebuffer and then
> trying to use eglSwapBuffers. But for some reason eglSwapBuffers was
> returning EGL_BAD_SURFACE even though eglMakeCurrent had no errors.

Can you render to it?  That sounds like something is wrong in the way
you're setting up your EGLSurface.  Of you can render you should be able to
blit.
--Jason
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