Bug 99033

Created attachment 128389 [details]
nvidia

could you tell us which extensions are actually needed? I am sure you can understand, that we can't simply implement all of the missing ones in a wink of an eye, so we have to prefer the important ones

Looking at the OpenGL 2.1 specification, I haven’t been able to find any extension, that was promoted to a core feature in OpenGL <= 2.1, that is not implemented by Nouveau.

Some of the extensions exposed by NVIDIA are clearly not part of the OpenGL 2.1 specification, such as GL_ARB_shading_language_420pack [0], which was approved in 2011, whereas the OpenGL 2.1 specification is from Dec. 2006.
I had a quick look at about 10 extensions exposed by NVIDIA but not by Nouveau, and they were mostly approved >2008. One extension, GL_EXT_framebuffer_multisample [1], was approved in 2005, but it became a core feature only in OpenGL 3.0.

From what I understand (correct me if I am wrong), OpenGL extensions, as long as they haven’t been made into a core feature, are completely optional in order to support a given OpenGL version.

[0]: https://www.opengl.org/registry/specs/ARB/shading_language_420pack.txt
[1]: https://www.opengl.org/registry/specs/EXT/framebuffer_multisample.txt

> could you tell us which extensions are actually needed?
In the source code, I spent kwin search for extensions by string ("GL_ and revealed the following files, which is held on the expansion test.

./kwin/effects/blur/blurshader.cpp
./kwin/eglonxbackend.cpp
./kwin/libkwineffects/kwinglplatform.cpp
./kwin/libkwineffects/kwingltexture.cpp
./kwin/libkwineffects/kwinglutils.cpp
./kwin/libkwineffects/kwinglutils_funcs.cpp
./kwin/scene_opengl.cpp

And determined the expansion are absent in nouveau, but there is nvidia.

GL_EXT_texture_format_BGRA8888
GL_ARB_framebuffer_object
GL_OES_mapbuffer
GL_OES_texture_3D

And also found that the extension is not in the nvidia, but there is in nouveau.

GL_OES_EGL_image

Problem effect is "Taskbar thumbnail"
./kwin/effects/taskbarthumbnail/*

When you mouse hover over a tab on the taskbar instead of the window shows a blank thumbnail translucent rectangle of the appropriate size.
When you switch on the OpenGL 1.2 kwin thumbnail is displayed.

Created attachment 128441 [details]
kde-workspace-4.11.22.tar.xz

(In reply to Ilya Indigo from comment #4)
> And determined the expansion are absent in nouveau, but there is nvidia.
> 
> GL_EXT_texture_format_BGRA8888
> GL_OES_mapbuffer
> GL_OES_texture_3D

These are ES extensions and not available in a desktop GL profile, on nvidia or nouveau. They should, however, be present on a mesa ES profile. See https://people.freedesktop.org/~imirkin/glxinfo/#p=es&v=Mesa%2010.6.0

> GL_ARB_framebuffer_object

Yeah, we don't support that one while NVIDIA does. It requires a lot of work-arounding to handle all the cases not supported by the HW. Tripping those up gets you off the fastpath in the blob driver and it slows down bigtime. We have no such fallbacks in nouveau.

However GL_EXT_framebuffer_object is supported, and doesn't allow the unsupportable conditions (like attachments of different sizes).

> Problem effect is "Taskbar thumbnail"
> ./kwin/effects/taskbarthumbnail/*
> 
> When you mouse hover over a tab on the taskbar instead of the window shows a
> blank thumbnail translucent rectangle of the appropriate size.
> When you switch on the OpenGL 1.2 kwin thumbnail is displayed.

That sounds like you're hitting a situation where you have a depth buffer that's incompatible with the color buffer. We're supposed to fall back in that situation, but don't. As a result, there's no depth, which can lead to no rendering. Once this is supported, we could probably look at supporting ARB_framebuffer_object, as similar mechanisms would be required.

Is there a link to the code I could glance at to see if that's likely the issue?

> Looking at the OpenGL 2.1 specification, I haven’t been able to find any extension, that was promoted to a core feature in OpenGL <= 2.1, that is not implemented by Nouveau.

If this card is able to support later expansion, which should be implemented to the later video card, which shows a list of nvidia, why not add them to this card?

> could you tell us which extensions are actually needed? I am sure you can understand, that we can't simply implement all of the missing ones in a wink of an eye, so we have to prefer the important ones.

I thought, if in Mesa for nouveau declared support for OpenGL 4.1 at least, the increasingly younger expansion should be implemented already, just depending on the graphics card will connect them to a different set?

Or something I do not understand, and for each GPU you write from scratch every extension?

> Is there a link to the code I could glance at to see if that's likely the issue?
You mean the source code kwin?
I have it attached.
https://bugs.freedesktop.org/attachment.cgi?id=128441

(In reply to Ilya Indigo from comment #7)
> If this card is able to support later expansion, which should be implemented
> to the later video card, which shows a list of nvidia, why not add them to
> this card?

They are using software to work around the hardware's limitations. That software is not written for nouveau.

> I thought, if in Mesa for nouveau declared support for OpenGL 4.1 at least,

For GF100+ GPUs, yes. NV67 is a fair bit older.

> the increasingly younger expansion should be implemented already, just
> depending on the graphics card will connect them to a different set?
> 
> Or something I do not understand, and for each GPU you write from scratch
> every extension?

Each hardware generation supports what it supports. For NV67, which is effectively a NV4x, that's basically the DX9 feature set. ARB_framebuffer_object is, in essence, a DX10 feature, but NVIDIA was able to provide the software fallbacks for the cases in the ext that aren't handled, and fast-path the cases that are. Nouveau hasn't done this. Patches welcome.

(In reply to Ilya Indigo from comment #8)
> > Is there a link to the code I could glance at to see if that's likely the issue?
> You mean the source code kwin?
> I have it attached.
> https://bugs.freedesktop.org/attachment.cgi?id=128441

https://github.com/KDE/kde-workspace/blob/KDE/4.11/kwin/effects/taskbarthumbnail/taskbarthumbnail.cpp

Unfortunately this is too abstract in order for me to tell how it works under the hood.

I might recommend building this with DEBUG_GLRENDERTARGET and seeing if you hit any issues. (At least in the code, this causes a bunch of error checking to be activated.)

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