Hi Uwe, many thanks for your help! :)
Yeah, seems that Qt5 && X11 && 'xcb' backend with the Qwt 6.2 and QwtPlotOpenGLCanvas does help a bit. The iMX6 CPU usage now is ~50% (instead of previous 100%). PS: But compilation for latest Qwt version from trunk r2921 fails, please look on this my post: https://www.qtcentre.org/threads/69743-Qwt-6-3-0-(from-qwt-code-r2921-trunk)-compilation-fails-on-Ubuntu-18-04?p=303603#post303603 BR, Denis чт, 30 авг. 2018 г. в 10:46, Uwe Rathmann <uwe.rathm...@tigertal.de>: > On Wed, 29 Aug 2018 16:43:40 +0300, Denis Shienkov wrote: > > > So, there are no way to improve an acceleration and to minimize the CPU > > loading? > > It depends on the requirements of your application, but when it comes to > oscilloscope alike widgets your best choice is Qt4/X11. > > The X11 paint engine is hardware accelerated, it even allows painting > outside of paint events - what is important for incremental painting. > > ( The fact, that Qt 4.8 prefers using raster with the argument of > performance it is totally nonsense, when it comes to any sort of vector > graphics. ) > > Furthermore the X11 paint engine simply has a better quality. The sort of > bugs coming and going with the various Qt versions is a nightmare for any > sort of graphics framework. Actually my job for today is to find a work > around for this one: https://bugreports.qt.io/browse/QTBUG-70101 > > -- > > If you need to go with Qt5 I would recommend to use a platform that > allows for using QOpenGlWidget - X11 again is IMHO not a bad choice. > Actually one of our terminals is a iMX6, where we do this ( because we > needed VNC support ). > > Next I recommend Qwt from SVN trunk, where you can simply assign a > QwtPlotOpenGLCanvas to achieve hardware acceleration. The quality of the > OpenGL paint engine is not as good as X11 or Raster, but for a > oscilloscope things usually do not need to be pixel perfect. > > -- > > Finally you should not ignore algorithmic options to reduce what has to > be painted. How to optimize the rendering process is often quite > individual, but often QwtPlotCurve::FilterPointsAggressive ( since Qwt > 6.2 ) has a significant effect in oscilloscope alike applications. > > In fact I have been contacted quite often with oscilloscope applications > struggling with performance issues and often it could be solved on a > algorithmic level. > > As an inspiration you could also try to run the oscilloscope demo of Qwt > on your board. You will notice, that it runs with almost no CPU usage > because it mostly paints incrementally. Of course this only works because > the design of the user interface is made for this, but maybe you can do > something similar. > > Uwe > > > _______________________________________________ > Development mailing list > Development@qt-project.org > http://lists.qt-project.org/mailman/listinfo/development >
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