Hi,
On 26/10/2016 08:21, Kai Koehne wrote:
-----Original Message-----
From: Liu, Jeff (SRDC SW) [mailto:jeff1....@amd.com]
Sent: Wednesday, October 26, 2016 7:09 AM
To: gunnar.sle...@jollamobile.com; gun...@sletta.org; Liang Qi
<liang...@qt.io>; Kai Koehne <kai.koe...@qt.io>; development@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.sle...@jollamobile.com'; 'gun...@sletta.org'; 'liang...@qt.io';
'kai.koe...@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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