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# glwidget.cpp Example File
opengl/pbuffers2/glwidget.cpp

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    **
    ** This file is part of the example classes of the Qt Toolkit.
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    ** accordance with the Qt Preview License Agreement provided with the
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    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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    #include <QtGui/QImage>
    #include "glwidget.h"

    #include <math.h>

    #ifndef GL_MULTISAMPLE
    #define GL_MULTISAMPLE  0x809D
    #endif

    GLWidget::GLWidget(QWidget *parent)
        : QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
    {
        setWindowTitle(tr("OpenGL pbuffers 2"));

        pbuffer = new QGLPixelBuffer(512, 512, format(), this);

        rot_x = rot_y = rot_z = 0.0f;
        scale = 0.1f;
        anim = new QTimeLine(750, this);
        anim->setUpdateInterval(20);
        connect(anim, SIGNAL(valueChanged(qreal)), SLOT(animate(qreal)));
        connect(anim, SIGNAL(finished()), SLOT(animFinished()));

        svg_renderer = new QSvgRenderer(QLatin1String(":/res/bubbles.svg"), this);
        connect(svg_renderer, SIGNAL(repaintNeeded()), this, SLOT(draw()));

        logo = QImage(":/res/qt4-logo.png");
        logo = logo.convertToFormat(QImage::Format_ARGB32);

        makeCurrent(); // need a current context to create the display list
        tile_list = glGenLists(1);
        glNewList(tile_list, GL_COMPILE);
        glBegin(GL_QUADS);
        {
            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);

            glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
            glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);

            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);

            glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
            glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);

            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
            glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);

            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
    }
        glEnd();
        glEndList();

        wave = new GLfloat[logo.width()*logo.height()];
        memset(wave, 0, logo.width()*logo.height());
        startTimer(30); // wave timer

        pbuffer->makeCurrent();
        dynamicTexture = pbuffer->generateDynamicTexture();

        // bind the dynamic texture to the pbuffer - this is a no-op under X11
        pbuffer->bindToDynamicTexture(dynamicTexture);
    }

    GLWidget::~GLWidget()
    {
        delete[] wave;
        glDeleteLists(tile_list, 1);
        pbuffer->releaseFromDynamicTexture();
        glDeleteTextures(1, &dynamicTexture);
        delete pbuffer;
    }

    void GLWidget::paintEvent(QPaintEvent *)
    {
        draw();
    }

    void GLWidget::draw()
    {
        QPainter p(this); // used for text overlay

        // save the GL state set for QPainter
        saveGLState();

        // render the 'bubbles.svg' file into our pbuffer
        QPainter pbuffer_painter(pbuffer);
        svg_renderer->render(&pbuffer_painter);
        pbuffer_painter.end();
        glFlush();

    #if  defined(Q_WS_X11)
        // rendering directly to a texture is not supported on X11, unfortunately
        pbuffer->updateDynamicTexture(dynamicTexture);
    #endif

        makeCurrent();
        // draw into the GL widget
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glFrustum(-1, 1, -1, 1, 10, 100);
        glTranslatef(0.0f, 0.0f, -15.0f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glViewport(0, 0, width(), height());

        glBindTexture(GL_TEXTURE_2D, dynamicTexture);
        glEnable(GL_TEXTURE_2D);
        glEnable(GL_MULTISAMPLE);
        glEnable(GL_CULL_FACE);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        // draw background
        glPushMatrix();
        glScalef(1.7f, 1.7f, 1.7f);
        glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
        glCallList(tile_list);
        glPopMatrix();

        const int w = logo.width();
        const int h = logo.height();

        glRotatef(rot_x, 1.0f, 0.0f, 0.0f);
        glRotatef(rot_y, 0.0f, 1.0f, 0.0f);
        glRotatef(rot_z, 0.0f, 0.0f, 1.0f);
        glScalef(scale/w, scale/w, scale/w);

        glDepthFunc(GL_LESS);
        glEnable(GL_DEPTH_TEST);

        // draw the Qt icon
        glTranslatef(-w+1, -h+1, 0.0f);
        for (int y=h-1; y>=0; --y) {
            uint *p = (uint*) logo.scanLine(y);
            uint *end = p + w;
            int  x = 0;
            while (p < end) {
                glColor4ub(qRed(*p), qGreen(*p), qBlue(*p), uchar(qAlpha(*p)*.9));
                glTranslatef(0.0f, 0.0f, wave[y*w+x]);
                if (qAlpha(*p) > 128)
                    glCallList(tile_list);
                glTranslatef(0.0f, 0.0f, -wave[y*w+x]);
                glTranslatef(2.0f, 0.0f, 0.0f);
                ++x;
                ++p;
            }
            glTranslatef(-w*2.0f, 2.0f, 0.0f);
        }

        // restore the GL state that QPainter expects
        restoreGLState();

        // draw the overlayed text using QPainter
        p.setPen(QColor(197, 197, 197, 157));
        p.setBrush(QColor(197, 197, 197, 127));
        p.drawRect(QRect(0, 0, width(), 50));
        p.setPen(Qt::black);
        p.setBrush(Qt::NoBrush);
        const QString str1(tr("A simple OpenGL pbuffer example."));
        const QString str2(tr("Use the mouse wheel to zoom, press buttons and move mouse to rotate, double-click to flip."));
        QFontMetrics fm(p.font());
        p.drawText(width()/2 - fm.width(str1)/2, 20, str1);
        p.drawText(width()/2 - fm.width(str2)/2, 20 + fm.lineSpacing(), str2);
    }

    void GLWidget::mousePressEvent(QMouseEvent *e)
    {
        anchor = e->pos();
    }

    void GLWidget::mouseMoveEvent(QMouseEvent *e)
    {
        QPoint diff = e->pos() - anchor;
        if (e->buttons() & Qt::LeftButton) {
            rot_x += diff.y()/5.0f;
            rot_y += diff.x()/5.0f;
        } else if (e->buttons() & Qt::RightButton) {
            rot_z += diff.x()/5.0f;
        }

        anchor = e->pos();
        draw();
    }

    void GLWidget::wheelEvent(QWheelEvent *e)
    {
        e->delta() > 0 ? scale += scale*0.1f : scale -= scale*0.1f;
        draw();
    }

    void GLWidget::mouseDoubleClickEvent(QMouseEvent *)
    {
        anim->start();
    }

    void GLWidget::animate(qreal val)
    {
        rot_y = val * 180;
        draw();
    }

    void GLWidget::animFinished()
    {
        if (anim->direction() == QTimeLine::Forward)
            anim->setDirection(QTimeLine::Backward);
        else
            anim->setDirection(QTimeLine::Forward);
    }

    void GLWidget::saveGLState()
    {
        glPushAttrib(GL_ALL_ATTRIB_BITS);
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
    }

    void GLWidget::restoreGLState()
    {
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glPopAttrib();
    }

    #define PI 3.14159

    void GLWidget::timerEvent(QTimerEvent *)
    {
        if (QApplication::mouseButtons() != 0)
            return;

        static bool scale_in = true;

        if (scale_in && scale > 35.0f)
            scale_in = false;
        else if (!scale_in && scale < .5f)
            scale_in = true;

        scale = scale_in ? scale + scale*0.01f : scale-scale*0.01f;
        rot_z += 0.3f;
        rot_x += 0.1f;

        int dx, dy; // disturbance point
        float s, v, W, t;
        int i, j;
        static float wt[128][128];
        const int width = logo.width();
        const int AMP = 5;

        dx = dy = width >> 1;

        W = .3f;
        v = -4; // wave speed

        for (i = 0; i < width; ++i) {
            for ( j = 0; j < width; ++j) {
                s = sqrt((double) ((j - dx) * (j - dx) + (i - dy) * (i - dy)));
                wt[i][j] += 0.1f;
                t = s / v;
                if (s != 0)
                    wave[i*width + j] = AMP * sin(2 * PI * W * (wt[i][j] + t)) / (0.2*(s + 2));
                else
                    wave[i*width + j] = AMP * sin(2 * PI * W * (wt[i][j] + t));
            }
        }
    }