Something wrong whit QOpenGLWidget and QOpenGLFunctions.

[zhengbing]

Hello All:
I use QOpenGLShaderProgram, QOpenGLShader, and so on. QT's class can render very successful. But when I try to use opengl's API directly, get nothing on screen. Is there something wrong? Please help me. Thanks! Code as follow:

class Widget : public QOpenGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT
public:
    Widget(QWidget *parent = 0);
    ~Widget();
protected:
    virtual void initializeGL();
    virtual void paintGL();
    virtual void resizeGL(int w, int h);
private:
    QMatrix4x4  m_projectionMat;
    GLint       m_pMatrixUniform;
    GLuint vertexAttributeBuffer;
};

Widget::Widget(QWidget *parent) : QOpenGLWidget(parent)
{
}

Widget::~Widget()
{
}
void Widget::initializeGL()
{
    initializeOpenGLFunctions();
    glViewport(0, 0, width()*devicePixelRatio(), height()*devicePixelRatio());
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
    glClearColor(0, 0, 0, 1);

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    const char * vertexShaderCode =
            "attribute highp vec3 aVertexPosition;  \
             uniform mat4 uPMatrix;                 \
             void main(void) {                      \
                 gl_Position = uPMatrix * vec4(aVertexPosition, 1.0); \
             }";
    glShaderSource(vertexShader,1,&vertexShaderCode,NULL);
    glCompileShader(vertexShader);

    GLint success;
    GLchar infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        qWarning() << "ERROR::SHADER::VERTEX::COMPILATION_FAILED" << infoLog;
    }

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    const char * fragmentShaderCode =
            "void main(void) {                  \
                 gl_FragColor = vec4(1.0, 1.0, 0.0,1.0);    \
             }";
    glShaderSource(fragmentShader, 1, &fragmentShaderCode, NULL);
    glCompileShader(fragmentShader);
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        qWarning() << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED" << infoLog;
    }

    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if(!success)
    {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        qWarning() << "ERROR::SHADER_PROGRAM::LINK_FAILED" << infoLog;
    }
    glUseProgram(shaderProgram);

    GLint positionLocation = glGetAttribLocation(shaderProgram,"aVertexPosition");
    glEnableVertexAttribArray(positionLocation);
    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);
    m_pMatrixUniform = glGetUniformLocation(shaderProgram, "uPMatrix");

    glGenBuffers(1, &vertexAttributeBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexAttributeBuffer);   //缓存对象此刻被真正创建
    GLfloat data[] = {
        0.0, 2.0, -3.0,
        0.0, 0.0, -3.0,
        2.0, 0.0, -3.0
    };
    glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);
}

void Widget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glUniformMatrix4fv(m_pMatrixUniform, 1, GL_FALSE, m_projectionMat.constData());
    glBindBuffer(GL_ARRAY_BUFFER, vertexAttributeBuffer);
    glDrawArrays(GL_TRIANGLES, 0, 3);
}

void Widget::resizeGL(int w, int h)
{
    m_projectionMat.setToIdentity();
    m_projectionMat.perspective(45.0, w/h, 1.0, 6.0);
}

Thanks again.