Qt 5.9 | Qt Quick | Qt Quick Widgets Example | fbitem.cpp Example File

Qt 5.9.9 Reference Documentation

# fbitem.cpp Example File

quickwidgets/quickwidget/fbitem.cpp

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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() : c(0), dir(1) { }

          // 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() {
              qDebug("FbRenderer destroyed");
          }

          void render() {
              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) {
              qDebug() << "Creating FBO" << size;
              QOpenGLFramebufferObjectFormat format;
              format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
              return new QOpenGLFramebufferObject(size, format);
          }

      private:
          float c;
          int dir;
      };
      #endif

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