Mailing List Archive

Qt on OpenGL on macOS
This was on the "Qt Interest" mailing list. I thought it worth
repeating here. MythTV doesn't use QQuickWidget, but we might run into
problems whenever Apple gets around to removing OpenGL.

David

-------- Forwarded Message --------
From: Sze Howe Koh <szehowe.koh@gmail.com>
To: Dirk Hohndel <dirk@hohndel.org>, interestqt-project.org
<interest@qt-project.org>
Subject: Re: [Interest] Creating fat binaries for Qt6 on macOS
Date: Wed, 13 Apr 2022 21:52:39 +0800

Apple has let their OpenGL implementation stagnate since 2010 [1].
They then officially deprecated it in 2018, citing significant
advantages of Metal over OpenGL [2]. They have not revealed when
OpenGL will be removed.

Most of Qt Quick works well with Metal -- it's only QQuickWidget that
doesn't. In contrast, the graphics API setting affects all of Qt
Quick. Furthermore, QQuickWidget has limitations [3] compared to other
ways of displaying a Qt Quick UI, so it shouldn't be the first choice
unless you really need to mix widgets with Qt Quick.

Given all this, I don't think it makes sense for Qt to default to
something that can be killed off any day now, just to make it easier
to use QQuickWidget.

In any case, I think the error message "QQuickWidget is only supported
on OpenGL. Use QQuickWindow::setGraphicsApi() to override the default"
is clear enough as a once-off message for those who want to use
QQuickWidget.


Regards,
Sze-Howe

[1] https://support.apple.com/en-us/HT202823
[2]
https://venturebeat.com/2018/06/06/apple-defends-end-of-opengl-as-mac-game-developers-threaten-to-leave/
[3] https://doc.qt.io/qt-6/qquickwidget.html#performance-considerations
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Re: Qt on OpenGL on macOS [ In reply to ]
On Wed, Apr 13, 2022 at 3:31 PM David Hampton via mythtv-dev <
mythtv-dev@mythtv.org> wrote:

> This was on the "Qt Interest" mailing list. I thought it worth
> repeating here. MythTV doesn't use QQuickWidget, but we might run into
> problems whenever Apple gets around to removing OpenGL.
>

I'll caveat this by stating that implementing any macOS updates for OpenGL
and Metal are way out of my current skill set / knowledge base (but I'll be
happy to help where I can).

Would something like Google's ANGLE <https://github.com/google/angle> or
metalANGLE <https://github.com/kakashidinho/metalangle> be helpful?

There's also MGL <https://github.com/openglonmetal/MGL> which seems to be
an implementation of OpenGL 4.6 that runs on top of metal.