Stupid question about QT6 and OpenGL support

[Mattia Verga]

While in the process of updating celestia package to the latest
snapshot, I was trying to build it with qt interface and opengl_ES for
rendering. But looking at the build logs of qt6-qtbase:
OpenGL:
     Desktop OpenGL ....................... yes
     OpenGL ES 2.0 ........................ no
     OpenGL ES 3.0 ........................ no
     OpenGL ES 3.1 ........................ no
     OpenGL ES 3.2 ........................ no

it doesn't seem that qt6-qtbase is built with OpenGL_ES support.
Is it something it can be easily enabled, so that I can, perhaps, use
openGL_ES rendering on aarch64 for celestia? Or there's no advantage to
have both Desktop and ES support? Can I expect any performance
improvement on aarch64 by using ES? (I don't have any raspberry or other
device for testing)

Mattia

[Neal Gompa]

On Sat, Dec 3, 2022 at 9:25 AM Mattia Verga via devel
<devel(a)lists.fedoraproject.org&gt; wrote:
>  While in the process of updating celestia package to the latest
>  snapshot, I was trying to build it with qt interface and opengl_ES for
>  rendering. But looking at the build logs of qt6-qtbase:
>  OpenGL:
>       Desktop OpenGL ....................... yes
>       OpenGL ES 2.0 ........................ no
>       OpenGL ES 3.0 ........................ no
>       OpenGL ES 3.1 ........................ no
>       OpenGL ES 3.2 ........................ no
>
>  it doesn't seem that qt6-qtbase is built with OpenGL_ES support.
>  Is it something it can be easily enabled, so that I can, perhaps, use
>  openGL_ES rendering on aarch64 for celestia? Or there's no advantage to
>  have both Desktop and ES support? Can I expect any performance
>  improvement on aarch64 by using ES? (I don't have any raspberry or other
>  device for testing)
>  
As far as I know, Qt can only be built with one mode or another. So
it's a mutually exclusive choice. Also, it looks like we don't have
the GLES libraries from Mesa at all to even make that choice. :(



-- 
真実はいつも一つ！/ Always, there's only one truth!

[Mattia Verga]

Il 03/12/22 16:29, Neal Gompa ha scritto:

>  As far as I know, Qt can only be built with one mode or another. So
>  it's a mutually exclusive choice. Also, it looks like we don't have
>  the GLES libraries from Mesa at all to even make that choice. :( 
So, why glxinfo on my system returns:

>  OpenGL vendor string: AMD
>  OpenGL renderer string: AMD Radeon Graphics (renoir, LLVM 15.0.0, DRM 3.48,
> 6.0.10-300.fc37.
>  x86_64)
>  OpenGL core profile version string: 4.6 (Core Profile) Mesa 22.2.3
>  OpenGL core profile shading language version string: 4.60
>  OpenGL core profile context flags: (none)
>  OpenGL core profile profile mask: core profile
>
>  OpenGL version string: 4.6 (Compatibility Profile) Mesa 22.2.3
>  OpenGL shading language version string: 4.60
>  OpenGL context flags: (none)
>  OpenGL profile mask: compatibility profile
>
>  OpenGL ES profile version string: OpenGL ES 3.2 Mesa 22.2.3
>  OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

[Neal Gompa]

On Sat, Dec 3, 2022 at 12:43 PM Mattia Verga via devel
<devel(a)lists.fedoraproject.org&gt; wrote:
>  Il 03/12/22 16:29, Neal Gompa ha scritto:
>
>
>  As far as I know, Qt can only be built with one mode or another. So
>  it's a mutually exclusive choice. Also, it looks like we don't have
>  the GLES libraries from Mesa at all to even make that choice. :(
>
>  So, why glxinfo on my system returns:
>
>  OpenGL vendor string: AMD
>  OpenGL renderer string: AMD Radeon Graphics (renoir, LLVM 15.0.0, DRM 3.48,
> 6.0.10-300.fc37.
>  x86_64)
>  OpenGL core profile version string: 4.6 (Core Profile) Mesa 22.2.3
>  OpenGL core profile shading language version string: 4.60
>  OpenGL core profile context flags: (none)
>  OpenGL core profile profile mask: core profile
>
>  OpenGL version string: 4.6 (Compatibility Profile) Mesa 22.2.3
>  OpenGL shading language version string: 4.60
>  OpenGL context flags: (none)
>  OpenGL profile mask: compatibility profile
>
>  OpenGL ES profile version string: OpenGL ES 3.2 Mesa 22.2.3
>  OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
>  
Good question, I don't know. Seems glvnd provides the libraries, maybe
that's enough?



-- 
真実はいつも一つ！/ Always, there's only one truth!

[Mattia Verga]

Il 03/12/22 19:01, Neal Gompa ha scritto:
>  Good question, I don't know. Seems glvnd provides the libraries, maybe
>  that's enough? 
I had a look at mesa specfile, first it is build with
   -Dgles1=disabled \
   -Dgles2=enabled \

but then:

# XXX can we just not build this
rm -vf %{buildroot}%{_libdir}/libGLES*

... I wonder why... AFAIK, GLES should be better for low resource
systems like raspberry, isn't it?

Mattia

[Kevin Kofler]

Mattia Verga via devel wrote:
>  ... I wonder why... AFAIK, GLES should be better for low resource
>  systems like raspberry, isn't it? 
Probably yes. KDE upstream recommends it for Plasma Mobile, and Manjaro ARM 
builds a few qt5-es2-* packages (conflicting with the regular qt5-* ones) 
for the components where it makes a difference. Fedora could do the same on 
aarch64.

And proprietary drivers for ARM often support ONLY OpenGL ES, so if we do 
not have Qt builds built for ES, Qt will not support OpenGL with those 
drivers at all. (Though it can be argued that that is a feature. ;-) )

As I understand it, Mesa now supports desktop OpenGL everywhere, but missing 
functionality is emulated in software, which is obviously slow.

        Kevin Kofler