04 -- QT OpenGL two sets of shaders draw two triangles

qmyopenglwidget.h

#ifndef QMYOPENGLWIDGET_H
#define QMYOPENGLWIDGET_H

#include <QWidget>
#include <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLShaderProgram>

class QMyOpenglWidget : public QOpenGLWidget, QOpenGLFunctions_3_3_Core
{
    Q_OBJECT
public:
    explicit QMyOpenglWidget(QWidget* parent = nullptr);

protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();

public:
    void cretaeShader(QOpenGLShaderProgram& program, QString vShaderFile, QString fShaderFile);
    void initTrianggleData(GLuint &vao, float* vertices, GLuint &ebo);

private:
    unsigned int vao1;
    unsigned int vao2;
    unsigned int ebo1;
    unsigned int ebo2;
    QOpenGLShaderProgram program1;
    QOpenGLShaderProgram program2;


signals:

public slots:


};

#endif // QMYOPENGLWIDGET_H

qmyopenglwidget.cpp

#include "qmyopenglwidget.h"

QMyOpenglWidget::QMyOpenglWidget(QWidget* parent):QOpenGLWidget(parent)
{

}

void QMyOpenglWidget::initializeGL()
{
    initializeOpenGLFunctions();

    float vertices1[] = {
        -1.0, 0, 0,
        1.0, 0, 0,
        0, 1.0f, 0
    };

    float vertices2[] = {
        -1.0, 0, 0,
        1.0, 0, 0,
        0, -0.5f, 0
    };
    QString vShaderFile = ":/shader/vertex.vert";
    QString fShaderFile = ":/shader/frag.frag";
    cretaeShader(program1, vShaderFile, fShaderFile);
    initTrianggleData(vao1, vertices1, ebo1);

    QString vShaderFile2 = ":/shader/vertex2.vert";
    QString fShaderFile2 = ":/shader/frag2.frag";

    cretaeShader(program2, vShaderFile2, fShaderFile2);
    initTrianggleData(vao2, vertices2, ebo2);

}

void QMyOpenglWidget::initTrianggleData(GLuint &vao, float* vertices, GLuint &ebo)
{
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);


    unsigned int vbo1;
    glGenBuffers(1, &vbo1);
    glBindBuffer(GL_ARRAY_BUFFER, vbo1);
    // Is currently bound to target  Create a new data store for the buffer object   //
    glBufferData(GL_ARRAY_BUFFER,  9 * sizeof(GL_FLOAT), vertices, GL_STATIC_DRAW);
    // Tell the graphics card how to parse the attribute value in the buffer 
    glVertexAttribPointer(0, 3, GL_FLOAT, FALSE, 3*sizeof (GL_FLOAT), nullptr);
    // Turn on VAO The first attribute of Management 
    glEnableVertexAttribArray(0);


    unsigned int indexs[] = {
        0, 1, 2
    };
    glGenBuffers(1, &ebo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indexs), indexs, GL_STATIC_DRAW);

    glBindVertexArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}

void QMyOpenglWidget::resizeGL(int w, int h)
{

}

void QMyOpenglWidget::paintGL()
{
    glClearColor(0.2f, 0.2f, 0.1f, 0.1f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo1);
    program1.bind();
    glBindVertexArray(vao1);
    glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, nullptr);
    program2.bind();
    glBindVertexArray(vao2);
    glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, nullptr);
    update();
}

void QMyOpenglWidget::cretaeShader(QOpenGLShaderProgram& program, QString vShaderFile, QString fShaderFile)
{
    program.addShaderFromSourceFile(QOpenGLShader::Vertex, vShaderFile);
    program.addShaderFromSourceFile(QOpenGLShader::Fragment, fShaderFile);
    program.bind();
    program.link();
}

vertex.vert

#version 330 core
in vec3 pos;

void main(void)
{
    gl_Position = vec4(pos, 1.0f);
}

frag.frag

#version 330 core
out vec4 FragColor; // Clip shader output 
void main(void)
{
    FragColor = vec4(0.8, 0.8, 0.1, 1.0);
}

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