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Does Qt Charts use OpenQL?

  • I made a real-time graph similar to the qmloscilloscope demo that updates at 60fps. It works nicely when small, but if I show it full-screen it noticeably misses frames. The qmloscilloscope demo also skips frames when running full screen.
    Does the QML ChartView use OpenGL for rendering? **

    Reading the documentation for QML Oscilloscope, there are tips to improve performance that lead me to believe it is a legacy component that has not been brought up-to-date with the OpenGL support in Qt 5, such as the recommendation to use the startup parameter: -graphicssystem opengl. "graphicssystem" was removed in Qt 5.1, I'm on Qt 5.5.

    I'm drawing about 600 line segments -- I would not expect that to be an issue for OpenGL. The performance feels like it is not hardware accelerated. Also, my GPU shows 0% utilization while running qmloscilloscope and my graphing app. All evidence points to software rendering. Perhaps it renders to an OpenGL buffer, but I do not think it is uses OpenGL line drawing operations.

  • I got my answer yesterday; the just-released Qt Charts 2.1.0 supports OpenGL, but version 2.0 did not. I re-ran the Oscilloscope demo using the Qt 5.6.0 beta Qt Charts and it is orders of magnitudes faster than before and clearly fast enough for my purposes.

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