- Qt 5.5
- Qt OpenGL
- Hello GL2 Example
- glwidget.cpp Example File
- Qt 5.5.1 Reference Documentation

# glwidget.cpp Example File

hellogl2/glwidget.cpp

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
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    #include "glwidget.h"
    #include <QMouseEvent>
    #include <QOpenGLShaderProgram>
    #include <QCoreApplication>
    #include <math.h>

    GLWidget::GLWidget(QWidget *parent)
        : QOpenGLWidget(parent),
          m_xRot(0),
          m_yRot(0),
          m_zRot(0),
          m_program(0)
    {
        m_core = QCoreApplication::arguments().contains(QStringLiteral("--coreprofile"));
        // --transparent causes the clear color to be transparent. Therefore, on systems that
        // support it, the widget will become transparent apart from the logo.
        m_transparent = QCoreApplication::arguments().contains(QStringLiteral("--transparent"));
        if (m_transparent)
            setAttribute(Qt::WA_TranslucentBackground);
    }

    GLWidget::~GLWidget()
    {
        cleanup();
    }

    QSize GLWidget::minimumSizeHint() const
    {
        return QSize(50, 50);
    }

    QSize GLWidget::sizeHint() const
    {
        return QSize(400, 400);
    }

    static void qNormalizeAngle(int &angle)
    {
        while (angle < 0)
            angle += 360 * 16;
        while (angle > 360 * 16)
            angle -= 360 * 16;
    }

    void GLWidget::setXRotation(int angle)
    {
        qNormalizeAngle(angle);
        if (angle != m_xRot) {
            m_xRot = angle;
            emit xRotationChanged(angle);
            update();
        }
    }

    void GLWidget::setYRotation(int angle)
    {
        qNormalizeAngle(angle);
        if (angle != m_yRot) {
            m_yRot = angle;
            emit yRotationChanged(angle);
            update();
        }
    }

    void GLWidget::setZRotation(int angle)
    {
        qNormalizeAngle(angle);
        if (angle != m_zRot) {
            m_zRot = angle;
            emit zRotationChanged(angle);
            update();
        }
    }

    void GLWidget::cleanup()
    {
        makeCurrent();
        m_logoVbo.destroy();
        delete m_program;
        m_program = 0;
        doneCurrent();
    }

    static const char *vertexShaderSourceCore =
        "#version 150\n"
        "in vec4 vertex;\n"
        "in vec3 normal;\n"
        "out vec3 vert;\n"
        "out vec3 vertNormal;\n"
        "uniform mat4 projMatrix;\n"
        "uniform mat4 mvMatrix;\n"
        "uniform mat3 normalMatrix;\n"
        "void main() {\n"
        "   vert = vertex.xyz;\n"
        "   vertNormal = normalMatrix * normal;\n"
        "   gl_Position = projMatrix * mvMatrix * vertex;\n"
        "}\n";

    static const char *fragmentShaderSourceCore =
        "#version 150\n"
        "in highp vec3 vert;\n"
        "in highp vec3 vertNormal;\n"
        "out highp vec4 fragColor;\n"
        "uniform highp vec3 lightPos;\n"
        "void main() {\n"
        "   highp vec3 L = normalize(lightPos - vert);\n"
        "   highp float NL = max(dot(normalize(vertNormal), L), 0.0);\n"
        "   highp vec3 color = vec3(0.39, 1.0, 0.0);\n"
        "   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);\n"
        "   fragColor = vec4(col, 1.0);\n"
        "}\n";

    static const char *vertexShaderSource =
        "attribute vec4 vertex;\n"
        "attribute vec3 normal;\n"
        "varying vec3 vert;\n"
        "varying vec3 vertNormal;\n"
        "uniform mat4 projMatrix;\n"
        "uniform mat4 mvMatrix;\n"
        "uniform mat3 normalMatrix;\n"
        "void main() {\n"
        "   vert = vertex.xyz;\n"
        "   vertNormal = normalMatrix * normal;\n"
        "   gl_Position = projMatrix * mvMatrix * vertex;\n"
        "}\n";

    static const char *fragmentShaderSource =
        "varying highp vec3 vert;\n"
        "varying highp vec3 vertNormal;\n"
        "uniform highp vec3 lightPos;\n"
        "void main() {\n"
        "   highp vec3 L = normalize(lightPos - vert);\n"
        "   highp float NL = max(dot(normalize(vertNormal), L), 0.0);\n"
        "   highp vec3 color = vec3(0.39, 1.0, 0.0);\n"
        "   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);\n"
        "   gl_FragColor = vec4(col, 1.0);\n"
        "}\n";

    void GLWidget::initializeGL()
    {
        // In this example the widget's corresponding top-level window can change
        // several times during the widget's lifetime. Whenever this happens, the
        // QOpenGLWidget's associated context is destroyed and a new one is created.
        // Therefore we have to be prepared to clean up the resources on the
        // aboutToBeDestroyed() signal, instead of the destructor. The emission of
        // the signal will be followed by an invocation of initializeGL() where we
        // can recreate all resources.
        connect(context(), &QOpenGLContext::aboutToBeDestroyed, this, &GLWidget::cleanup);

        initializeOpenGLFunctions();
        glClearColor(0, 0, 0, m_transparent ? 0 : 1);

        m_program = new QOpenGLShaderProgram;
        m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, m_core ? vertexShaderSourceCore : vertexShaderSource);
        m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, m_core ? fragmentShaderSourceCore : fragmentShaderSource);
        m_program->bindAttributeLocation("vertex", 0);
        m_program->bindAttributeLocation("normal", 1);
        m_program->link();

        m_program->bind();
        m_projMatrixLoc = m_program->uniformLocation("projMatrix");
        m_mvMatrixLoc = m_program->uniformLocation("mvMatrix");
        m_normalMatrixLoc = m_program->uniformLocation("normalMatrix");
        m_lightPosLoc = m_program->uniformLocation("lightPos");

        // Create a vertex array object. In OpenGL ES 2.0 and OpenGL 2.x
        // implementations this is optional and support may not be present
        // at all. Nonetheless the below code works in all cases and makes
        // sure there is a VAO when one is needed.
        m_vao.create();
        QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);

        // Setup our vertex buffer object.
        m_logoVbo.create();
        m_logoVbo.bind();
        m_logoVbo.allocate(m_logo.constData(), m_logo.count() * sizeof(GLfloat));

        // Store the vertex attribute bindings for the program.
        setupVertexAttribs();

        // Our camera never changes in this example.
        m_camera.setToIdentity();
        m_camera.translate(0, 0, -1);

        // Light position is fixed.
        m_program->setUniformValue(m_lightPosLoc, QVector3D(0, 0, 70));

        m_program->release();
    }

    void GLWidget::setupVertexAttribs()
    {
        m_logoVbo.bind();
        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
        f->glEnableVertexAttribArray(0);
        f->glEnableVertexAttribArray(1);
        f->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), 0);
        f->glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), reinterpret_cast<void *>(3 * sizeof(GLfloat)));
        m_logoVbo.release();
    }

    void GLWidget::paintGL()
    {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glEnable(GL_DEPTH_TEST);
        glEnable(GL_CULL_FACE);

        m_world.setToIdentity();
        m_world.rotate(180.0f - (m_xRot / 16.0f), 1, 0, 0);
        m_world.rotate(m_yRot / 16.0f, 0, 1, 0);
        m_world.rotate(m_zRot / 16.0f, 0, 0, 1);

        QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);
        m_program->bind();
        m_program->setUniformValue(m_projMatrixLoc, m_proj);
        m_program->setUniformValue(m_mvMatrixLoc, m_camera * m_world);
        QMatrix3x3 normalMatrix = m_world.normalMatrix();
        m_program->setUniformValue(m_normalMatrixLoc, normalMatrix);

        glDrawArrays(GL_TRIANGLES, 0, m_logo.vertexCount());

        m_program->release();
    }

    void GLWidget::resizeGL(int w, int h)
    {
        m_proj.setToIdentity();
        m_proj.perspective(45.0f, GLfloat(w) / h, 0.01f, 100.0f);
    }

    void GLWidget::mousePressEvent(QMouseEvent *event)
    {
        m_lastPos = event->pos();
    }

    void GLWidget::mouseMoveEvent(QMouseEvent *event)
    {
        int dx = event->x() - m_lastPos.x();
        int dy = event->y() - m_lastPos.y();

        if (event->buttons() & Qt::LeftButton) {
            setXRotation(m_xRot + 8 * dy);
            setYRotation(m_yRot + 8 * dx);
        } else if (event->buttons() & Qt::RightButton) {
            setXRotation(m_xRot + 8 * dy);
            setZRotation(m_zRot + 8 * dx);
        }
        m_lastPos = event->pos();
    }