关于Qt5.4 QOpenGLWidget 和QPainter 混合渲染有关问题

关于Qt5.4 QOpenGLWidget 和QPainter 混合渲染问题
Qt助手上说可以混合渲染：
It is also possible to draw 2D graphics onto a QOpenGLWidget subclass using QPainter:
1.In paintGL(), instead of issuing OpenGL commands, construct a QPainter object for use on the widget.
2.Draw primitives using QPainter's member functions.
3.Direct OpenGL commands can still be issued. However, you must make sure these are enclosed by a call to the painter's beginNativePainting() and endNativePainting().

我做了个实验，计划是显示一个三角形和一行文字，结果只能显示三角形，文字显示不出来。我的代码如下：

class Render : public QOpenGLWidget

{

public:

    Render();

    ~Render();

protected:

    void initializeGL();

    void paintGL();

    void resizeGL(int  w ,int h);

    QOpenGLFunctions_3_3_Core * f;

    QOpenGLBuffer * triangle;

    QOpenGLVertexArrayObject * vao;

    QOpenGLShaderProgram * program;

    QMatrix4x4 mv,p;

    QTimer * time;

    float rota;

    QPainter * painter;

    bool needInit;

    //void paintEvent(QPaintEvent *e);

 

};

.cpp

#include "render.h"

GLfloat tri[] =

{

    0.0f,1.0f,-1.0f,1.0f,

    1.0f,1.0f,-1.0f,1.0f,

    1.0f,0.0f,-1.0f,1.0f,

 

};

Render::Render()

{

    QSurfaceFormat format;

    format.setDepthBufferSize(24);

    format.setStencilBufferSize(8);

    // format.setVersion(3,3);

    //format.setProfile(QSurfaceFormat::CoreProfile);

 

    setFormat( format);

    rota = 1.5;

    needInit = true;

    //setAutoFillBackground(false);

    time =  new QTimer;

    connect(time,SIGNAL(timeout()),this,SLOT(update()));

    time->start(50);

}

 

Render::~Render()

{

 

}

void Render::initializeGL()

{

    f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_3_Core>();

    f->initializeOpenGLFunctions();

 

    //f = context()->functions();

 

}

void Render::resizeGL(int w ,int h)

{

 

    p.setToIdentity();

    p.perspective(35.0f,float(w)/float(h),1.0f,30.0f);

 

}

 

void Render::paintGL()

{

    QPainter pntr(this);

    // painter->setViewport(50,50,100,100);

    pntr.beginNativePainting();

    QOpenGLShaderProgram  programs ;

    programs.addShaderFromSourceCode(QOpenGLShader::Vertex,

                                     "#version 330 core \n\

                                    layout(location = 0) in vec4 vertex;\

           uniform mat4 mvp;\

   void main() \

   {\

       gl_Position = mvp * vertex;\

   }");

 

    programs.addShaderFromSourceCode(QOpenGLShader::Fragment,

                                     "#version 330 core \n\

                                    out vec4 fragColor;\

           void main() \

   { \

       fragColor = vec4(0.0f,1.0f,0.0f,1.0f);\

   }");

    programs.link();

 

    QOpenGLVertexArrayObject vaos;

    vaos.create();

    f->glBindVertexArray(vaos.objectId());

    QOpenGLBuffer triangles(QOpenGLBuffer::VertexBuffer);

    triangles.create();

    f->glBindBuffer(GL_ARRAY_BUFFER,triangles.bufferId());

    triangles.setUsagePattern(QOpenGLBuffer::DynamicDraw);

    triangles.allocate(tri,sizeof(tri));

    programs.enableAttributeArray(0);

    programs.setAttributeBuffer(0,GL_FLOAT,0,4,0);

 

    f->glEnable(GL_DEPTH_TEST);

 

    needInit = false;

 

    // this->makeCurrent();

    f->glViewport(0,0,width(),height());

    f->glClearColor(1.0f,0.5f,0.5f,1.0f);

    f->glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);

 

    programs.bind();

    mv.setToIdentity();

 

    mv.lookAt(QVector3D(0.0f,0.0f,5.0f),QVector3D(0.0f,0.0f,0.0f),QVector3D(0.0f,1.0f,0.0f));

    mv.rotate(0.5+rota,0,1,0);

    programs.setUniformValue("mvp",p*mv);

    f->glBindVertexArray(vaos.objectId());

    f->glDrawArrays(GL_TRIANGLES,0,3);

    rota=rota+1.5;

 

    pntr.endNativePainting();

 

    pntr.drawText(50,100,"Look This!");

 

}

------解决思路----------------------
Qt 5.4这点比较新，全靠你们大力探索了，成功后麻烦写一篇日志。