[Interest] [qt-android] Is it possible to create OpenGL ES 2 context even when ES 3 is available?

[Liang Jian]

     Can you take a look at http://community.arm.com/message/16669
     As you have said, Using GLSL 3 with GL_OES_EGL_image_external is not
permitted, but using GLSL 1 with GL_OES_EGL_image_external under opengl es
3 context is more like a hack according to the post.
GL_OES_EGL_image_external_essl3 should be the right way but I didn't find a
phone support that extension.
     According to my test, at least in my Meizu MX4 (with PowerVR Rogue
Han) I fail to compile the fragment shader with GL_OES_EGL_image_external,
other phone with opengl es 3 works fine. I guess if I can create a opengl
es 2 context maybe I can make it work. But As you have said Qt will request
2.0 context, and it is the implentation choose openges 3 context, then It
seems that it is a bug of the driver. But I am curious about how can this
phone pass through the Android CTS test? Android CTS test will use
SurfaceTexture and GL_OES_EGL_image_external

On Thu, Mar 12, 2015 at 5:42 PM, Agocs Laszlo <laszlo.agocs at theqtcompany.com
> wrote:

>  Qt does exactly what you ask for: it requests a 2.0 context. Now since
> implementations are free to return a later version that is backwards
> compatible with the requested, getting a 3.0 or 3.1 context is perfectly
> fine (and is the standard behavior you will get with any driver that
> supports ES 3.0 and newer).
>
>  There is no reason for GL_OES_EGL_image_external not to work with ES
> 3.x, as long as you use ES2-style (ESSL1) shaders. The typical problem is
> that drivers are free to reject it in ESSL3 shaders, unless they also
> support the fairly fresh GL_OES_EGL_image_external_essl3.
>
>
>
> Now, it could be that your particular driver disables the extension
> completely in non-2.0 contexts (regardless of the shading language version
> in use), but there is no solution to that since there is no standard way to
> force a given context version.
>
>
>
> Best regards,
>
> Laszlo
>
>
>
>
>
> *From:* interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org
> [mailto:interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org] *On
> Behalf Of *Liang Jian
> *Sent:* 12. mars 2015 08:02
> *To:* interest at qt-project.org
> *Subject:* [Interest] [qt-android] Is it possible to create OpenGL ES 2
> context even when ES 3 is available?
>
>
>
>      Now qt-android will create an OpenGL ES 3 context if that ES3 is
> supported by the devices even if I have call
> QSurfaceFormat::setVersion(2,0). Is it a way to just create the specific
> version I wanted using QOpenGLContext?
>
>     The reason why I care about that is: I need to use SurfaceTexture in
> my android app, and that require GL_OES_EGL_image_external extenstion, but
> GL_OES_EGL_image_external is written against OpenGL ES 2. If I create a
> OpenGL ES 3 context, some GPU (such as PowerVR rogue han) driver will fail
> to compile my fragment shader if I add the line to my fragment shader:
>     #extension GL_OES_EGL_image_external : require
>
>     In this case I must create a OpenGL ES 2 context to make it work.
>
>     I think qtmultimedia for android will also suffer from this because it
> will also use GL_OES_EGL_image_external. In fact I tried to deloy qmlvideo
> example to my Meizu MX4 (PowerVR Rogue Han) it didin't work, But I didn't
> see the shader compilation error from debug output.
>
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