fbitem.cpp Example File

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 #include "fbitem.h"
 #include <QtGui/QOpenGLFramebufferObject>
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QOpenGLFunctions>
 #include <QtCore/QDebug>

 #if QT_CONFIG(opengl)
 class FbRenderer : public QQuickFramebufferObject::Renderer
 {
 public:
     FbRenderer() { }

     // The lifetime of the FBO and this class depends on how QQuickWidget
     // manages the scenegraph and context when it comes to showing and hiding
     // the widget. The actual behavior is proven by the debug prints.
     ~FbRenderer() override {
         qDebug("FbRenderer destroyed");
     }

     void render() override {
         QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
         f->glClearColor(c, 0, 0, 1);
         f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
         c += 0.01f * dir;
         if (c >= 1.0f || c <= 0.0f)
             dir *= -1;
         update();
     }

     QOpenGLFramebufferObject *createFramebufferObject(const QSize &size) override {
         qDebug() << "Creating FBO" << size;
         QOpenGLFramebufferObjectFormat format;
         format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
         return new QOpenGLFramebufferObject(size, format);
     }

 private:
     float c = 0;
     int dir = 1;
 };
 #endif

 QQuickFramebufferObject::Renderer *FbItem::createRenderer() const
 {
 #if QT_CONFIG(opengl)
     return new FbRenderer;
 #else
     return nullptr;
 #endif
 }