- Qt 5.5
- Qt Widgets
- Composition Modes
- composition.cpp Example File
- Qt 5.5.1 Reference Documentation

# composition.cpp Example File

painting/composition/composition.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the demonstration applications of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:LGPL21$
    ** Commercial License Usage
    ** Licensees holding valid commercial Qt licenses may use this file in
    ** accordance with the commercial license agreement provided with the
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    ** information use the contact form at http://www.qt.io/contact-us.
    **
    ** GNU Lesser General Public License Usage
    ** Alternatively, this file may be used under the terms of the GNU Lesser
    ** General Public License version 2.1 or version 3 as published by the Free
    ** Software Foundation and appearing in the file LICENSE.LGPLv21 and
    ** LICENSE.LGPLv3 included in the packaging of this file. Please review the
    ** following information to ensure the GNU Lesser General Public License
    ** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
    ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
    **
    ** As a special exception, The Qt Company gives you certain additional
    ** rights. These rights are described in The Qt Company LGPL Exception
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    ** $QT_END_LICENSE$
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    ****************************************************************************/

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

    const int animationInterval = 15; // update every 16 ms = ~60FPS

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

        QGroupBox *mainGroup = new QGroupBox(parent);
        mainGroup->setTitle(tr("Composition Modes"));

        QGroupBox *modesGroup = new QGroupBox(mainGroup);
        modesGroup->setTitle(tr("Mode"));

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

        rbPlus = new QRadioButton(tr("Plus"), modesGroup);
        connect(rbPlus, SIGNAL(clicked()), view, SLOT(setPlusMode()));
        rbMultiply = new QRadioButton(tr("Multiply"), modesGroup);
        connect(rbMultiply, SIGNAL(clicked()), view, SLOT(setMultiplyMode()));
        rbScreen = new QRadioButton(tr("Screen"), modesGroup);
        connect(rbScreen, SIGNAL(clicked()), view, SLOT(setScreenMode()));
        rbOverlay = new QRadioButton(tr("Overlay"), modesGroup);
        connect(rbOverlay, SIGNAL(clicked()), view, SLOT(setOverlayMode()));
        rbDarken = new QRadioButton(tr("Darken"), modesGroup);
        connect(rbDarken, SIGNAL(clicked()), view, SLOT(setDarkenMode()));
        rbLighten = new QRadioButton(tr("Lighten"), modesGroup);
        connect(rbLighten, SIGNAL(clicked()), view, SLOT(setLightenMode()));
        rbColorDodge = new QRadioButton(tr("Color Dodge"), modesGroup);
        connect(rbColorDodge, SIGNAL(clicked()), view, SLOT(setColorDodgeMode()));
        rbColorBurn = new QRadioButton(tr("Color Burn"), modesGroup);
        connect(rbColorBurn, SIGNAL(clicked()), view, SLOT(setColorBurnMode()));
        rbHardLight = new QRadioButton(tr("Hard Light"), modesGroup);
        connect(rbHardLight, SIGNAL(clicked()), view, SLOT(setHardLightMode()));
        rbSoftLight = new QRadioButton(tr("Soft Light"), modesGroup);
        connect(rbSoftLight, SIGNAL(clicked()), view, SLOT(setSoftLightMode()));
        rbDifference = new QRadioButton(tr("Difference"), modesGroup);
        connect(rbDifference, SIGNAL(clicked()), view, SLOT(setDifferenceMode()));
        rbExclusion = new QRadioButton(tr("Exclusion"), modesGroup);
        connect(rbExclusion, SIGNAL(clicked()), view, SLOT(setExclusionMode()));

        QGroupBox *circleColorGroup = new QGroupBox(mainGroup);
        circleColorGroup->setTitle(tr("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->setTitle(tr("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(tr("Show Source"));
    #if defined(USE_OPENGL) && !defined(QT_OPENGL_ES)
        QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
        enableOpenGLButton->setText(tr("Use OpenGL"));
        enableOpenGLButton->setCheckable(true);
        enableOpenGLButton->setChecked(view->usesOpenGL());

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

        QPushButton *animateButton = new QPushButton(mainGroup);
        animateButton->setText(tr("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);
    #if defined(USE_OPENGL) && !defined(QT_OPENGL_ES)
        mainGroupLayout->addWidget(enableOpenGLButton);
    #endif

        QGridLayout *modesLayout = new QGridLayout(modesGroup);
        modesLayout->addWidget(rbClear, 0, 0);
        modesLayout->addWidget(rbSource, 1, 0);
        modesLayout->addWidget(rbDest, 2, 0);
        modesLayout->addWidget(rbSourceOver, 3, 0);
        modesLayout->addWidget(rbDestOver, 4, 0);
        modesLayout->addWidget(rbSourceIn, 5, 0);
        modesLayout->addWidget(rbDestIn, 6, 0);
        modesLayout->addWidget(rbSourceOut, 7, 0);
        modesLayout->addWidget(rbDestOut, 8, 0);
        modesLayout->addWidget(rbSourceAtop, 9, 0);
        modesLayout->addWidget(rbDestAtop, 10, 0);
        modesLayout->addWidget(rbXor, 11, 0);

        modesLayout->addWidget(rbPlus, 0, 1);
        modesLayout->addWidget(rbMultiply, 1, 1);
        modesLayout->addWidget(rbScreen, 2, 1);
        modesLayout->addWidget(rbOverlay, 3, 1);
        modesLayout->addWidget(rbDarken, 4, 1);
        modesLayout->addWidget(rbLighten, 5, 1);
        modesLayout->addWidget(rbColorDodge, 6, 1);
        modesLayout->addWidget(rbColorBurn, 7, 1);
        modesLayout->addWidget(rbHardLight, 8, 1);
        modesLayout->addWidget(rbSoftLight, 9, 1);
        modesLayout->addWidget(rbDifference, 10, 1);
        modesLayout->addWidget(rbExclusion, 11, 1);

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

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

        view->loadDescription(":res/composition/composition.html");
        view->loadSourceFile(":res/composition/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()));
    #if defined(USE_OPENGL) && !defined(QT_OPENGL_ES)
        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_animationTimer = startTimer(animationInterval);
        m_image = QImage(":res/composition/flower.jpg");
        m_image.setAlphaChannel(QImage(":res/composition/flower_alpha.jpg"));
        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 USE_OPENGL
        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::setAnimationEnabled(bool enabled)
    {
        if (m_animation_enabled == enabled)
            return;
        m_animation_enabled = enabled;
        if (enabled) {
            Q_ASSERT(!m_animationTimer);
            m_animationTimer = startTimer(animationInterval);
        } else {
            killTimer(m_animationTimer);
            m_animationTimer = 0;
        }
    }

    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() / qreal(2) + (qCos(t*8/11) + qSin(-t)) * width() / qreal(4);
        qreal y = height() / qreal(2) + (qSin(t*6/7) + qCos(t * qreal(1.5))) * height() / qreal(4);

        setCirclePos(QLineF(m_circle_pos, QPointF(x, y)).pointAt(0.02));
    }

    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 defined(USE_OPENGL) && !defined(QT_OPENGL_ES)
        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);
                p.end();
                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(); // Needed when using the GL1 engine
                p.beginNativePainting(); // Needed when using the GL2 engine

                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.endNativePainting(); // Needed when using the GL2 engine
                p.restore(); // Needed when using the GL1 engine

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

            painter->beginNativePainting(); // Needed when using the GL2 engine
            glWidget()->makeCurrent(); // Needed when using the GL1 engine
            glBindTexture(GL_TEXTURE_2D, m_compositing_tex);
            glEnable(GL_TEXTURE_2D);
            glEnable(GL_BLEND);
            glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
            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);
            painter->endNativePainting(); // Needed when using the GL2 engine
        } 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.byteCount());

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

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

    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;
        }
        if (m_animation_enabled) {
            killTimer(m_animationTimer);
            m_animationTimer = 0;
        }
    }

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

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

        if (m_animation_enabled) {
            Q_ASSERT(!m_animationTimer);
            m_animationTimer = startTimer(animationInterval);
        }
    }

    void CompositionRenderer::timerEvent(QTimerEvent *event)
    {
        if (event->timerId() == m_animationTimer)
            updateCirclePos();
    }

    void CompositionRenderer::setCirclePos(const QPointF &pos)
    {
        const QRect oldRect = rectangle_around(m_circle_pos).toAlignedRect();
        m_circle_pos = pos;
        const QRect newRect = rectangle_around(m_circle_pos).toAlignedRect();
    #if defined(USE_OPENGL) && !defined(QT_OPENGL_ES)
        if (usesOpenGL()) {
            update();
            return;
        }
    #endif
        update(oldRect | newRect);
    }