Graphics on Raspberry Pi with Qt 5

Given at Raspberry Pi Community meetup #14 at CLBC.
http://raspberrypi-tw-bdfa45.kktix.cc/events/meetup14

* Integrating OpenGL code into Qt 5 with the new QOpenGL* classes.
* Cross-compiling Qt for Raspbian, where those new classes are not generally available.[*]
* Next-generation support libraries Qt 3D and Qt 3D Canvas (not related with each other) coming with Qt 5.7.

[*]: You might also be interested in my cross-compiling notes.
https://gist.github.com/uranusjr/91c0086109e6c35bbbe48a0b6a405f78

Transcript

1. Graphics on Raspberry Pi
   with Qt 5
   

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2. Agenda
   • OpenGL and Gt
   • Cross-compiling Qt 5.6
   • Next generation 3D rendering
   

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3. Me
   • Call me TP
   • Follow @uranusjr
   • https://uranusjr.com
   

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4. www. .com
   

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5. Why Qt?
   • OpenGL is tedious
   • Long history of integration
   • Qt Quick and QML
   • Continuous improvements
   

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6. #include
   #include
   int main(int argc, char *argv[])
   {
   QApplication app(argc, argv);
   QWidget w;
   w.show();
   return app.exec();
   }
   

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8. How?
   • Widgets
   • Put things inside a widget
   • Put widgets in a window
   • Show windows in an application
   

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9. How?
   • Widgets
   • Add common GUI controls
   • Put widgets in a window
   • Show windows in an application
   

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10. How?
    • Widgets
    • Draw things with OpenGL
    • Put widgets in a window
    • Show windows in an application
    

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11. C++ Classes
    • QOpenGLWidget
    • QOpenGLContext
    • QOpenGLFunctions
    

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12. #include
    class MyWidget : public QOpenGLWidget
    {
    protected:
    // One-off settings.
    virtual void initializeGL();
    // Set projection. Called on resizing.
    virtual void resizeGL(int w, int h);
    // Do actual OpenGL painting.
    virtual void paintGL();
    }
    

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13. /usr/lib/x86_64-linux-gnu/qt5/examples/gui/openglwindow/
    

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14. Read the docs.
    http://doc.qt.io/qt-5/qopenglwidget.html
    

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15. Problems?
    • Legacy QtOpenGL module
    • Raspbian updates slowly
    • We want newer Qt
    

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16. Cross-Compiling
    • More up-to-date Qt distribution
    • Better support for add-on modules
    • Advanced tuning (if you want to)
    

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17. Read the wiki.
    https://wiki.qt.io/RaspberryPi_Beginners_Guide
    

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18. Read my notes.
    http://bit.ly/rpi-qt5-cross-compile
    

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19. Demo
    

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20. Qt 3D
    • Based on OpenGL
    • Simple C++ or QML usage
    • Quite powerful
    

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21. Qt 3D Canvas
    • Based on OpenGL
    • JavaScript API in Qt Quick
    • Modelled from WebGL
    • three.js port!
    

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