Opengl rendering quad

Question

For some reason, the quad that I'm rendering doesn't show and it only renders a black screen. I've checked the code multiple times and couldn't find the problem maybe someone can see what I don't see!

The purpose is to have a quad that follows the camera, right now I just want to show the quad with a single color, but all I get is a black screen. I am using QOpenGLWindow and QOpenGLFunctions.

void CSLFWindow::renderQuad()
{
    float x0 = -(float)1.f, y0 = -(float)1.f;
    float x1 = (float)1.f, y1 = (float)1.f;

    const QVector3D vertices[4] = {
        QVector3D( x0, y0, 0.0f),
        QVector3D( x0, y1, 0.0f),
        QVector3D( x1, y1, 0.0f),
        QVector3D( x1, y0, 0.0f)
    };

    const QVector3D normals[4] = {
        QVector3D(0.0f, 0.0f,1.0f),
        QVector3D(0.0f, 0.0f,1.0f),
        QVector3D(0.0f, 0.0f,1.0f),
        QVector3D(0.0f, 0.0f,1.0f)
    };
    const QVector2D texcoords[4] = {
        QVector2D(0.0f, 1.0f),
        QVector2D(0.0f, 0.0f),
        QVector2D(1.0f, 0.0f),
        QVector2D(1.0f, 1.0f)
    };

      const unsigned int indices[4] = { 3, 2, 1, 0 };

    m_shaderProgram.enableAttributeArray("vVertices");
    m_shaderProgram.enableAttributeArray("vTexCoords");
    m_shaderProgram.enableAttributeArray("vNormals");

    m_shaderProgram.setAttributeArray("vVertices", vertices);
    m_shaderProgram.setAttributeArray("vTexCoords", texcoords);
    m_shaderProgram.setAttributeArray("vNormals", normals);

    glDrawElements(GL_QUADS, 4, GL_UNSIGNED_INT, indices);

    m_shaderProgram.disableAttributeArray("vVertices");
    m_shaderProgram.disableAttributeArray("vTexCoords");
    m_shaderProgram.disableAttributeArray("vNormals");
}

and the rendering:

void CSLFWindow::paintGL()
{
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

      m_shaderProgram.bind();

      m_model.setToIdentity();
      m_view = m_camera.toMatrix();
      QMatrix4x4 modelMatrix = m_model ;
      QMatrix4x4 modelViewMatrix = m_view * modelMatrix;


      QMatrix4x4 mvp = m_projection * modelViewMatrix;

      m_shaderProgram.setUniformValue("MV", modelViewMatrix);

      m_shaderProgram.setUniformValue("MVP", mvp);           
      m_shaderProgram.setUniformValue("P", m_projection);      

      renderQuad();
      m_shaderProgram.release();
}

I'm setting the projection matrix as:

m_view.setToIdentity();
float aspect = h / w;
m_projection.setToIdentity();
m_projection.perspective(
    m_fov,          
    aspect,         
    0.1f,           
    1000.0f);       

here are my camera parameters:

m_cameraPos   = QVector3D(0.0f, 0.0f,  3.0f);
m_cameraFront = QVector3D(0.0f, 0.0f,  -1.0f);
m_cameraUp    = QVector3D(0.0f, 1.0f,  0.0f); 

QMatrix4x4 toMatrix()
{
     QMatrix4x4 vMatrix;
     vMatrix.setToIdentity();
     vMatrix.lookAt(m_cameraPos,  QVector3D(0.0f, 0.0f,  0.0f), 
                    m_cameraUp);

     return vMatrix;
 }

and here is my vertex shader:

#version 330 core

layout (location = 0)in vec3 vVertices;
layout (location = 1)in vec2 vTexCoords;
layout (location = 2)in vec3 vNormals;

uniform mat4 MV;
uniform mat4 MVP;
uniform mat4 P;

out vec2 FragTexCoord;
out vec3 FragNormals;

void main()
{
   FragTexCoord = vTexCoords;
   FragNormals = vNormals;

   gl_Position = MVP * vec4(vVertices,1);
}

and my fragment shader:

#version 330 core

out vec4 fragmentColor;

in vec2 FragTexCoord;
in vec3 FragNormals;

void main()
{
    fragmentColor = vec4(1.0,1.0,1.0,1.0);
}

Answer 1

I found the problem was in setting the surface format! when I remove format.setProfile(QSurfaceFormat::CoreProfile); I see the quad. but I don't understand why it happens

Change GL_QUAD to GL_TRIANGLE_FAN and it will work:

glDrawElements(GL_TRIANGLE_FAN, 4, GL_UNSIGNED_INT, indices);

GL_QUAD is deprecated and is removed in core profile.

See further Legacy OpenGL - Removed functionality, OpenGL Context and Forward compatibility