[Development] OpenGL Issues in Qt5.7

[Sean Harmer]

And now Gunnar has just pointed out there is work in this area: :)

https://codereview.qt-project.org/#/c/166202/

Cheers,

Sean

On 26/10/2016 08:54, Sean Harmer wrote:
> Hi,
>
> On 26/10/2016 08:21, Kai Koehne wrote:
>>> -----Original Message-----
>>> From: Liu, Jeff (SRDC SW) [mailto:Jeff1.Liu at amd.com]
>>> Sent: Wednesday, October 26, 2016 7:09 AM
>>> To: gunnar.sletta at jollamobile.com; gunnar at sletta.org; Liang Qi
>>> <Liang.Qi at qt.io>; Kai Koehne <Kai.Koehne at qt.io>; development at qt-
>>> project.org
>>> Subject: RE: OpenGL Issues in Qt5.7
>>>
>>>
>>>
>>> Spread to Qt mail-list to ask for help.
>>>
>>>
>>>
>>> From: Liu, Jeff (SRDC SW)
>>> Sent: Tuesday, October 25, 2016 2:26 PM
>>> To: 'gunnar.sletta at jollamobile.com'; 'gunnar at sletta.org'; 
>>> 'liang.qi at qt.io';
>>> 'kai.koehne at qt.io'
>>> Subject: OpenGL Issues in Qt5.7
>>>
>>>
>>>
>>> Hi Sletta, Qi and Koehne,
>> Hi Jeff!
>>
>>> This is Jeff from AMD, recently a customer reports a game issue with 
>>> AMD
>>> cards, but the game runs well on Nvidia card, after some debug, I 
>>> find out
>>> that the issues are caused by Qt libraries, when Qt programs with 
>>> OpenGL
>>> API, it doesn’t follow the OpenGL programming specification 
>>> strictly, so it will
>>> report errors on AMD platform.
>>>
>>> Now we find out the two following issues, both issues come from Qt 
>>> paint
>>> engine.
>>>
>>> 1.       QTBUG-56234 - OpenGL glVertexAttribArray API usage error in
>>> Qt5Guid.dll
>>>
>>> I submit a ticket to address this issue, and this issue is assigned 
>>> to Sletta, but
>>> it seems no one starts to work on it, the usage of 
>>> glVertexAttribArray API is
>>> wrong, it is still used in the old way (OpenGL 3.0), but it 
>>> apparently violate the
>>> latest OpenGL specification (OpenGL 4.1)
>> Liang already commented on this one. Laszlo (the new assignee) probably
>> has a better idea about this, too.
>
> As commented on the bug, this QOpenGL2PaintEngine is only meant for 
> use with a 2.x OpenGL context. The paint engine will not work properly 
> with a Core Profile context. All the shaders are also legacy 
> (attribute + varying vs in + out).
>
>>
>>> 2.       I don’t submit the ticket for the second issue yet,  Qt 
>>> paint engine uses
>>> GL_RED to upload the texture, so based on the spec, the texture will be
>>> (GL_RED value, 0,0,1), but in pixel shader, it uses src * mask.a, 
>>> which is a
>>> constant 0 value in AMD platform, if changed to src * mask.r, then 
>>> everything
>>> will be correct, I will submit a ticket to address it later.
>> Feel free to report this, too.
>
> Again, this would really require a new OpenGL paint engine for modern 
> OpenGL to be written. Afaik nobody is working on this or even looking 
> into it. Using Qt Quick 2 would be an easier path if it suits your use 
> case. I'd love to have the ability to composite widget painting with 
> modern GL so if you want to work on such a thing then please do feel 
> free to do so.
>
> Cheers,
>
> Sean
>
>
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