[Development] [QML] Avoiding graphics flicker in Quick2
Sean Harmer
sean.harmer at kdab.com
Fri Aug 5 11:03:37 CEST 2016
On Friday 05 August 2016 12:02:10 Denis Shienkov wrote:
> > Can you try a plain OpenGL test application with RGBA8 framebuffer
>
> Do you mean: I should take any OpenGL application from the Qt examples? And
> to check there?
You may need to modify it to explicitly request R8G8B8A8 using a
QSurfaceFormat but yes any of those should work to prove/disprove.
Sean
>
> 2016-08-05 11:53 GMT+03:00 Sean Harmer <sean.harmer at kdab.com>:
> > Hi,
> >
> > Can you try a plain OpenGL test application with RGBA8 framebuffer and see
> > if
> > that exhibits the same flashing/flickering problem. If so, it's a
> > driver/hardware issue.
> >
> > If you are forced into then using a 16-bit framebuffer, then you can avoid
> > the
> > banding by using dithering in your gradients. Either apply the dithering
> > offline
> > and store the gradients as images or write a custom material that applies
> > the
> > dithering in the fragment shader.
> >
> > Cheers,
> >
> > Sean
> >
> > On Friday 05 August 2016 08:12:59 Denis Shienkov wrote:
> > > Hi all,
> > >
> > > I have an idea how to avoid flickering, but I don't know about results:
> > > what if I will discard the Open GL support in favor to Quick2 render?
> > >
> > > I have read this documentation: http://doc.qt.io/QtQuick2DRenderer/
> > > which says about the "Qt Quick 2D Renderer" module.
> > >
> > > So, my things is:
> > >
> > > 1. Download && build && install this module:
> > >
> > > git://code.qt.io/qt/qtdeclarative-render2d.git
> > >
> > > 2. Use this env variable:
> > >
> > > export QMLSCENE_DEVICE=softwarecontext
> > >
> > > 3. Run my app...
> > >
> > >
> > > But, I don't understand:
> > >
> > > 1) What of engine is used to 2D rendering in case if I have EGLFS only?
> > >
> > > 2) Should I re-build Qt5 too with the "--no-opengl" option (or I can
> > > keep the "-opengl es2" option) ?
> > >
> > > 04.08.2016 16:10, Denis Shienkov пишет:
> > > > Hi Robin,
> > > >
> > > > > Repeating my last answer...
> > > > > http://lists.qt-project.org/pipermail/development/2016-> >
> > July/026736.html
> >
> > > > I'm sorry, but I did not receive (did not see) your last answer.
> > > >
> > > > > I'm going to guess you're using eglfs or something like that
> > > >
> > > > Yes, I use EGLFS via X11 on Linux Apalis T30 board, where are used
> > > > NVIDIA's drivers.
> > > >
> > > > Seems, the flickering is when are used:
> > > >
> > > > export QT_QPA_EGLFS_FORCE888=1
> > > >
> > > > ENV variable... (I need this variable to smooth the Image's
> > > > gradients... even X11 started with 24-bit depth).
> > > >
> > > > PS: But, I'm not sure about QT_QPA_EGLFS_FORCE888... :(
> > > >
> > > > > Using an overlay to debug item positions (QSG_VISUALIZE=overdraw)
> > > >
> > > > could be handy for trying to rule
> > > > this out, as if it is specific to the application,
> > > >
> > > > Ok, many thanks, I will try it.
> > > >
> > > >
> > > > 2016-08-04 14:57 GMT+03:00 Robin Burchell <robin+qt at viroteck.net
> > > >
> > > > <mailto:robin+qt at viroteck.net>>:
> > > > Repeating my last answer...
> > > >
> > > > http://lists.qt-project.org/pipermail/development/2016-> >
> > July/026736.htm
> >
> > > > l
> > > >
> > > > On Thu, Aug 4, 2016, at 01:50 PM, Denis Shienkov wrote:
> > > > > {quote}
> > > > >
> > > > > Hi all.
> > > > >
> > > > > I have some QML application, where just use QQuickView as QML
> > > >
> > > > container.
> > > >
> > > > > This application uses Qt 5.7.x and running on Linux embedded
> > > >
> > > > board with
> > > >
> > > > > the
> > > > > NVIDIA core (Toradex Apalis T30).
> > > > >
> > > > > But sometimes I got flickering in process of animation. A
> >
> > flickering
> >
> > > > > represents in form of a "white" strips with full-screen width
> > > >
> > > > and 1/5-1/6
> > > >
> > > > > screen heigth. This flickers happens quickly and frequently
> > > >
> > > > (every ~20-60
> > > >
> > > > > seconds, randomly)...
> > > > >
> > > > > I have seen this "Avoiding graphics flicker in Qt / QML" [1]
> > > >
> > > > blog where
> > > >
> > > > > are
> > > > > used QML with Qt 4.x,
> > > > > where were used this trics:
> > > > >
> > > > > {code}
> > > > > int main(int argc, char **argv)
> > > > > {
> > > > >
> > > > > ...
> > > > >
> > > > > view.setAttribute(Qt::WA_OpaquePaintEvent);
> > > > > view.setAttribute(Qt::WA_NoSystemBackground);
> > > > > view.viewport()->setAttribute(Qt::WA_OpaquePaintEvent);
> > > > > view.viewport()->setAttribute(Qt::WA_NoSystemBackground);
> > > > >
> > > > > ...
> > > > >
> > > > > }
> > > > > {code}
> > > > >
> > > > > But, in my case I have use Quick v2, with QQuickView instead of
> > > > > QDeclarativeView,
> > > > > which does not allowed to setup any attributes.
> > > > >
> > > > > So, my questions is: is there are any way to setup
> > > > > Qt::WA_OpaquePaintEvent
> > > > > and/or
> > > > > Qt::WA_NoSystemBackground in Quck2? Or, maybe is it possible to
> >
> > use
> >
> > > > > another
> > > > > tricks?
> > > > >
> > > > > BR,
> > > > > Denis
> > > >
> > > > [1]https://blog.rburchell.com/2011/11/avoiding-graphics-> >
> > flicker-in-qt-> > qml.html>
> >
> > > > > {quote}
> > > > >
> > > > > This flickering present on some HDMI displays...
> > > > >
> > > > > We currently have this flags:
> > > > >
> > > > > {code}
> > > > > ...
> > > > > view.setFlags(Qt::FramelessWindowHint |
> >
> > Qt::WindowStaysOnTopHint);
> >
> > > > > ...
> > > > > {code}
> > > > >
> > > > > Maybe is it an reasons of flikering? Has someone any ideas?
> > > > >
> > > > > BR,
> > > > > Denis
> > > > > _______________________________________________
> > > > > Development mailing list
> > > > > Development at qt-project.org <mailto:Development at qt-project.org>
> > > > > http://lists.qt-project.org/mailman/listinfo/development
> >
> > --
> > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
> > KDAB (UK) Ltd, a KDAB Group company
> > Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
> > Mobile: +44 (0)7545 140604
> > KDAB - Qt Experts
> > _______________________________________________
> > Development mailing list
> > Development at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/development
--
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
KDAB (UK) Ltd, a KDAB Group company
Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
Mobile: +44 (0)7545 140604
KDAB - Qt Experts
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