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composition.cpp Example File
^{demos/composition/composition.cpp}

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 #include "composition.h"
 #include <QBoxLayout>
 #include <QRadioButton>
 #include <QTimer>
 #include <QDateTime>
 #include <QSlider>
 #include <QMouseEvent>
 #include <math.h>

 CompositionWidget::CompositionWidget(QWidget *parent)
     : QWidget(parent)
 {
     CompositionRenderer *view = new CompositionRenderer(this);

     QGroupBox *mainGroup = new QGroupBox(parent);
     mainGroup->setAttribute(Qt::WA_ContentsPropagated);
     mainGroup->setTitle("Composition Modes");

     QGroupBox *modesGroup = new QGroupBox(mainGroup);
     modesGroup->setAttribute(Qt::WA_ContentsPropagated);
     modesGroup->setTitle("Mode");

     rbClear = new QRadioButton("Clear", modesGroup);
     connect(rbClear, SIGNAL(clicked()), view, SLOT(setClearMode()));
     rbSource = new QRadioButton("Source", modesGroup);
     connect(rbSource, SIGNAL(clicked()), view, SLOT(setSourceMode()));
     rbDest = new QRadioButton("Destination", modesGroup);
     connect(rbDest, SIGNAL(clicked()), view, SLOT(setDestMode()));
     rbSourceOver = new QRadioButton("Source Over", modesGroup);
     connect(rbSourceOver, SIGNAL(clicked()), view, SLOT(setSourceOverMode()));
     rbDestOver = new QRadioButton("Destination Over", modesGroup);
     connect(rbDestOver, SIGNAL(clicked()), view, SLOT(setDestOverMode()));
     rbSourceIn = new QRadioButton("Source In", modesGroup);
     connect(rbSourceIn, SIGNAL(clicked()), view, SLOT(setSourceInMode()));
     rbDestIn = new QRadioButton("Dest In", modesGroup);
     connect(rbDestIn, SIGNAL(clicked()), view, SLOT(setDestInMode()));
     rbSourceOut = new QRadioButton("Source Out", modesGroup);
     connect(rbSourceOut, SIGNAL(clicked()), view, SLOT(setSourceOutMode()));
     rbDestOut = new QRadioButton("Dest Out", modesGroup);
     connect(rbDestOut, SIGNAL(clicked()), view, SLOT(setDestOutMode()));
     rbSourceAtop = new QRadioButton("Source Atop", modesGroup);
     connect(rbSourceAtop, SIGNAL(clicked()), view, SLOT(setSourceAtopMode()));
     rbDestAtop = new QRadioButton("Dest Atop", modesGroup);
     connect(rbDestAtop, SIGNAL(clicked()), view, SLOT(setDestAtopMode()));
     rbXor = new QRadioButton("Xor", modesGroup);
     connect(rbXor, SIGNAL(clicked()), view, SLOT(setXorMode()));

     QGroupBox *circleColorGroup = new QGroupBox(mainGroup);
     circleColorGroup->setAttribute(Qt::WA_ContentsPropagated);
     circleColorGroup->setTitle("Circle color");
     QSlider *circleColorSlider = new QSlider(Qt::Horizontal, circleColorGroup);
     circleColorSlider->setRange(0, 359);
     circleColorSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     connect(circleColorSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleColor(int)));

     QGroupBox *circleAlphaGroup = new QGroupBox(mainGroup);
     circleAlphaGroup->setAttribute(Qt::WA_ContentsPropagated);
     circleAlphaGroup->setTitle("Circle alpha");
     QSlider *circleAlphaSlider = new QSlider(Qt::Horizontal, circleAlphaGroup);
     circleAlphaSlider->setRange(0, 255);
     circleAlphaSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     connect(circleAlphaSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleAlpha(int)));

     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText("Show Source");
 #ifdef QT_OPENGL_SUPPORT
     QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
     enableOpenGLButton->setText("Use OpenGL");
     enableOpenGLButton->setCheckable(true);
     enableOpenGLButton->setChecked(view->usesOpenGL());

     if (!QGLFormat::hasOpenGL() || !QGLPixelBuffer::hasOpenGLPbuffers())
         enableOpenGLButton->hide();
 #endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText("What's This?");
     whatsThisButton->setCheckable(true);

     QPushButton *animateButton = new QPushButton(mainGroup);
     animateButton->setText("Animated");
     animateButton->setCheckable(true);
     animateButton->setChecked(true);

     QHBoxLayout *viewLayout = new QHBoxLayout(this);
     viewLayout->addWidget(view);
     viewLayout->addWidget(mainGroup);

     QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
     mainGroupLayout->addWidget(circleColorGroup);
     mainGroupLayout->addWidget(circleAlphaGroup);
     mainGroupLayout->addWidget(modesGroup);
     mainGroupLayout->addStretch();
     mainGroupLayout->addWidget(animateButton);
     mainGroupLayout->addWidget(whatsThisButton);
     mainGroupLayout->addWidget(showSourceButton);
 #ifdef QT_OPENGL_SUPPORT
     mainGroupLayout->addWidget(enableOpenGLButton);
 #endif

     QVBoxLayout *modesLayout = new QVBoxLayout(modesGroup);
     modesLayout->addWidget(rbClear);
     modesLayout->addWidget(rbSource);
     modesLayout->addWidget(rbDest);
     modesLayout->addWidget(rbSourceOver);
     modesLayout->addWidget(rbDestOver);
     modesLayout->addWidget(rbSourceIn);
     modesLayout->addWidget(rbDestIn);
     modesLayout->addWidget(rbSourceOut);
     modesLayout->addWidget(rbDestOut);
     modesLayout->addWidget(rbSourceAtop);
     modesLayout->addWidget(rbDestAtop);
     modesLayout->addWidget(rbXor);

     QVBoxLayout *circleColorLayout = new QVBoxLayout(circleColorGroup);
     circleColorLayout->addWidget(circleColorSlider);

     QVBoxLayout *circleAlphaLayout = new QVBoxLayout(circleAlphaGroup);
     circleAlphaLayout->addWidget(circleAlphaSlider);

     view->loadDescription(":res/composition.html");
     view->loadSourceFile(":res/composition.cpp");

     connect(whatsThisButton, SIGNAL(clicked(bool)), view, SLOT(setDescriptionEnabled(bool)));
     connect(view, SIGNAL(descriptionEnabledChanged(bool)), whatsThisButton, SLOT(setChecked(bool)));
     connect(showSourceButton, SIGNAL(clicked()), view, SLOT(showSource()));
 #ifdef QT_OPENGL_SUPPORT
     connect(enableOpenGLButton, SIGNAL(clicked(bool)), view, SLOT(enableOpenGL(bool)));
 #endif
     connect(animateButton, SIGNAL(toggled(bool)), view, SLOT(setAnimationEnabled(bool)));

     circleColorSlider->setValue(270);
     circleAlphaSlider->setValue(200);
     rbSourceOut->animateClick();

     setWindowTitle(tr("Composition Modes"));
 }

 void CompositionWidget::nextMode()
 {
     /*
       if (!m_animation_enabled)
       return;
       if (rbClear->isChecked()) rbSource->animateClick();
       if (rbSource->isChecked()) rbDest->animateClick();
       if (rbDest->isChecked()) rbSourceOver->animateClick();
       if (rbSourceOver->isChecked()) rbDestOver->animateClick();
       if (rbDestOver->isChecked()) rbSourceIn->animateClick();
       if (rbSourceIn->isChecked()) rbDestIn->animateClick();
       if (rbDestIn->isChecked()) rbSourceOut->animateClick();
       if (rbSourceOut->isChecked()) rbDestOut->animateClick();
       if (rbDestOut->isChecked()) rbSourceAtop->animateClick();
       if (rbSourceAtop->isChecked()) rbDestAtop->animateClick();
       if (rbDestAtop->isChecked()) rbXor->animateClick();
       if (rbXor->isChecked()) rbClear->animateClick();
     */
 }

 CompositionRenderer::CompositionRenderer(QWidget *parent)
     : ArthurFrame(parent)
 {
     m_animation_enabled = true;
     m_image = QImage(":res/flower_2.png");
     m_circle_alpha = 127;
     m_circle_hue = 255;
     m_current_object = NoObject;
     m_composition_mode = QPainter::CompositionMode_SourceOut;

     m_circle_pos = QPoint(200, 100);

     setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
 #ifdef QT_OPENGL_SUPPORT
     m_pbuffer = 0;
     m_pbuffer_size = 1024;
 #endif
 }

 QRectF rectangle_around(const QPointF &p, const QSizeF &size = QSize(250, 200))
 {
     QRectF rect(p, size);
     rect.translate(-size.width()/2, -size.height()/2);
     return rect;
 }

 void CompositionRenderer::updateCirclePos()
 {
     if (m_current_object != NoObject)
         return;
     QDateTime dt = QDateTime::currentDateTime();
     qreal t = (dt.toTime_t() * 1000 + dt.time().msec()) / 1000.0;

     qreal x = width() / 2.0 + (cos(t) + sin(-t*2)) * width() / 2.0;
     qreal y = height() / 2.0 + (sin(t) + cos(t * 3)) * height() / 2.0;

     m_circle_pos = QLineF(m_circle_pos, QPointF(x, y)).pointAt(0.01);
 }

 void CompositionRenderer::drawBase(QPainter &p)
 {
     p.setPen(Qt::NoPen);

     QLinearGradient rect_gradient(0, 0, 0, height());
     rect_gradient.setColorAt(0, Qt::red);
     rect_gradient.setColorAt(.17, Qt::yellow);
     rect_gradient.setColorAt(.33, Qt::green);
     rect_gradient.setColorAt(.50, Qt::cyan);
     rect_gradient.setColorAt(.66, Qt::blue);
     rect_gradient.setColorAt(.81, Qt::magenta);
     rect_gradient.setColorAt(1, Qt::red);
     p.setBrush(rect_gradient);
     p.drawRect(width() / 2, 0, width() / 2, height());

     QLinearGradient alpha_gradient(0, 0, width(), 0);
     alpha_gradient.setColorAt(0, Qt::white);
     alpha_gradient.setColorAt(0.2, Qt::white);
     alpha_gradient.setColorAt(0.5, Qt::transparent);
     alpha_gradient.setColorAt(0.8, Qt::white);
     alpha_gradient.setColorAt(1, Qt::white);

     p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
     p.setBrush(alpha_gradient);
     p.drawRect(0, 0, width(), height());

     p.setCompositionMode(QPainter::CompositionMode_DestinationOver);

     p.setPen(Qt::NoPen);
     p.setRenderHint(QPainter::SmoothPixmapTransform);
     p.drawImage(rect(), m_image);
 }

 void CompositionRenderer::drawSource(QPainter &p)
 {
     p.setPen(Qt::NoPen);
     p.setRenderHint(QPainter::Antialiasing);
     p.setCompositionMode(m_composition_mode);

     QRectF circle_rect = rectangle_around(m_circle_pos);
     QColor color = QColor::fromHsvF(m_circle_hue / 360.0, 1, 1, m_circle_alpha / 255.0);
     QLinearGradient circle_gradient(circle_rect.topLeft(), circle_rect.bottomRight());
     circle_gradient.setColorAt(0, color.light());
     circle_gradient.setColorAt(0.5, color);
     circle_gradient.setColorAt(1, color.dark());
     p.setBrush(circle_gradient);

     p.drawEllipse(circle_rect);
 }

 void CompositionRenderer::paint(QPainter *painter)
 {
     if (m_animation_enabled)
         updateCirclePos();

 #ifdef QT_OPENGL_SUPPORT
     if (usesOpenGL()) {

         int new_pbuf_size = m_pbuffer_size;
         if (size().width() > m_pbuffer_size ||
             size().height() > m_pbuffer_size)
             new_pbuf_size *= 2;

         if (size().width() < m_pbuffer_size/2 &&
             size().height() < m_pbuffer_size/2)
             new_pbuf_size /= 2;

         if (!m_pbuffer || new_pbuf_size != m_pbuffer_size) {
             if (m_pbuffer) {
                 m_pbuffer->deleteTexture(m_base_tex);
                 m_pbuffer->deleteTexture(m_compositing_tex);
                 delete m_pbuffer;
             }

             m_pbuffer = new QGLPixelBuffer(QSize(new_pbuf_size, new_pbuf_size), QGLFormat::defaultFormat(), glWidget());
             m_pbuffer->makeCurrent();
             m_base_tex = m_pbuffer->generateDynamicTexture();
             m_compositing_tex = m_pbuffer->generateDynamicTexture();
             m_pbuffer_size = new_pbuf_size;
         }

         if (size() != m_previous_size) {
             m_previous_size = size();
             QPainter p(m_pbuffer);
             p.setCompositionMode(QPainter::CompositionMode_Source);
             p.fillRect(QRect(0, 0, m_pbuffer->width(), m_pbuffer->height()), Qt::transparent);
             drawBase(p);
             m_pbuffer->updateDynamicTexture(m_base_tex);
         }

         qreal x_fraction = width()/float(m_pbuffer->width());
         qreal y_fraction = height()/float(m_pbuffer->height());

         {
             QPainter p(m_pbuffer);
             p.setCompositionMode(QPainter::CompositionMode_Source);
             p.fillRect(QRect(0, 0, m_pbuffer->width(), m_pbuffer->height()), Qt::transparent);

             p.save();
             glBindTexture(GL_TEXTURE_2D, m_base_tex);
             glEnable(GL_TEXTURE_2D);
             glColor4f(1.,1.,1.,1.);

             glBegin(GL_QUADS);
             {
                 glTexCoord2f(0, 1.0);
                 glVertex2f(0, 0);

                 glTexCoord2f(x_fraction, 1.0);
                 glVertex2f(width(), 0);

                 glTexCoord2f(x_fraction, 1.0-y_fraction);
                 glVertex2f(width(), height());

                 glTexCoord2f(0, 1.0-y_fraction);
                 glVertex2f(0, height());
             }
             glEnd();

             glDisable(GL_TEXTURE_2D);
             p.restore();

             drawSource(p);
             m_pbuffer->updateDynamicTexture(m_compositing_tex);
         }

         glWidget()->makeCurrent();
         glBindTexture(GL_TEXTURE_2D, m_compositing_tex);
         glEnable(GL_TEXTURE_2D);
         glColor4f(1.,1.,1.,1.);
         glBegin(GL_QUADS);
         {
             glTexCoord2f(0, 1.0);
             glVertex2f(0, 0);

             glTexCoord2f(x_fraction, 1.0);
             glVertex2f(width(), 0);

             glTexCoord2f(x_fraction, 1.0-y_fraction);
             glVertex2f(width(), height());

             glTexCoord2f(0, 1.0-y_fraction);
             glVertex2f(0, height());
         }
         glEnd();
         glDisable(GL_TEXTURE_2D);
     } else
 #endif
     {
         // using a QImage
         if (m_buffer.size() != size()) {
             m_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
             m_base_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);

             m_base_buffer.fill(0);

             QPainter p(&m_base_buffer);

             drawBase(p);
         }

         memcpy(m_buffer.bits(), m_base_buffer.bits(), m_buffer.numBytes());

         {
             QPainter p(&m_buffer);
             drawSource(p);
         }

         painter->drawImage(0, 0, m_buffer);
     }

     if (m_animation_enabled)
         update();
 }

 void CompositionRenderer::mousePressEvent(QMouseEvent *e)
 {
     setDescriptionEnabled(false);

     QRectF circle = rectangle_around(m_circle_pos);

     if (circle.contains(e->pos())) {
         m_current_object = Circle;
         m_offset = circle.center() - e->pos();
     } else {
         m_current_object = NoObject;
     }
 }

 void CompositionRenderer::mouseMoveEvent(QMouseEvent *e)
 {
     if (m_current_object == Circle) setCirclePos(e->pos() + m_offset);
 }

 void CompositionRenderer::mouseReleaseEvent(QMouseEvent *)
 {
     m_current_object = NoObject;
 }