(Solved) [QT 5.2 OpenGL] Unable to draw triangles

alelink

Hi everyone,
I'm just stuck trying to draw triangles using QT5.2 and OpenGL 4.3.
Simply nothing is drawn on screen, I get backgroundColor only.

I have an OpenGLViewport class derived from QWindow, and in its constructor I do:
@
// Tell Qt we will use OpenGL for this window
setSurfaceType( OpenGLSurface );

// Specify the format we wish to use
QSurfaceFormat format;
format.setDepthBufferSize( 24 );
format.setMajorVersion( 4 );
format.setMinorVersion( 3 );
format.setSamples( 4 );
format.setProfile&#40; QSurfaceFormat::CoreProfile &#41;;

setFormat( format &#41;;
create();

// Create an OpenGL context
pContext = new QOpenGLContext;
pContext->setFormat( format );
pContext->create();

// Setup our scene
pContext->makeCurrent( this );

//init OpenGL
initializeGL();

// Make sure we tell OpenGL about new window sizes
connect( this, SIGNAL( widthChanged( int ) ), this, SLOT( resizeGL() ) );
connect( this, SIGNAL( heightChanged( int ) ), this, SLOT( resizeGL() ) );
resizeGL();

@

My initializeGL method is the following:
@
this->pContext->makeCurrent( this );

this->pOGLFunctions = pContext->versionFunctions<QOpenGLFunctions_4_3_Core>();
if ( !pOGLFunctions )
{
qFatal("Requires OpenGL >= 4.3");
exit( 1 );
}
this->pOGLFunctions->initializeOpenGLFunctions();

//backgroundColor
this->pOGLFunctions->glClearColor( 0.25f, 0.25f, 0.25f, 1.0f );
// Enable depth testing
this->pOGLFunctions->glEnable( GL_DEPTH_TEST );
this->pOGLFunctions->glEnable( GL_CULL_FACE );
@

this is what I'm doing to render triangles (it is a bit rough, I know, but it is just a test):
@
// Make the context current
this->pContext->makeCurrent( this );

//test code
// Shader sources
const GLchar* vertexSource =
"#version 150 core\n"
"in vec2 position;"
"in vec3 color;"
"out vec3 Color;"
"void main() {"
" Color = color;"
" gl_Position = vec4(position, 0.0, 1.0);"
"}";
const GLchar* fragmentSource =
"#version 150 core\n"
"in vec3 Color;"
"out vec4 outColor;"
"void main() {"
" outColor = vec4(Color, 1.0);"
"}";

// Create Vertex Array Object
GLuint vao;
this->pOGLFunctions->glGenVertexArrays(1, &vao);
this->pOGLFunctions->glBindVertexArray(vao);

// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
this->pOGLFunctions->glGenBuffers(1, &vbo);

GLfloat vertices[] = {
    -0.5f,  0.5f, 1.0f, 0.0f, 0.0f, // Top-left
     0.5f,  0.5f, 0.0f, 1.0f, 0.0f, // Top-right
     0.5f, -0.5f, 0.0f, 0.0f, 1.0f, // Bottom-right
    -0.5f, -0.5f, 1.0f, 1.0f, 1.0f  // Bottom-left
};

this->pOGLFunctions->glBindBuffer(GL_ARRAY_BUFFER, vbo);
this->pOGLFunctions->glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

err += glGetError();
// Create an element array
GLuint ebo;
this->pOGLFunctions->glGenBuffers(1, &ebo);

GLuint elements[] = {
    0, 1, 2,
    2, 3, 0
};

this->pOGLFunctions->glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
this->pOGLFunctions->glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

// Create and compile the vertex shader
GLuint vertexShader = this->pOGLFunctions->glCreateShader(GL_VERTEX_SHADER);
this->pOGLFunctions->glShaderSource(vertexShader, 1, &vertexSource, NULL);
this->pOGLFunctions->glCompileShader(vertexShader);

// Create and compile the fragment shader
GLuint fragmentShader = this->pOGLFunctions->glCreateShader(GL_FRAGMENT_SHADER);
this->pOGLFunctions->glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
this->pOGLFunctions->glCompileShader(fragmentShader);

// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = this->pOGLFunctions->glCreateProgram();
this->pOGLFunctions->glAttachShader(shaderProgram, vertexShader);
this->pOGLFunctions->glAttachShader(shaderProgram, fragmentShader);
this->pOGLFunctions->glBindFragDataLocation(shaderProgram, 0, "outColor");
this->pOGLFunctions->glLinkProgram(shaderProgram);
this->pOGLFunctions->glUseProgram(shaderProgram);

// Specify the layout of the vertex data
GLint posAttrib = this->pOGLFunctions->glGetAttribLocation(shaderProgram, "position");
this->pOGLFunctions->glEnableVertexAttribArray(posAttrib);
this->pOGLFunctions->glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), 0);

GLint colAttrib = this->pOGLFunctions->glGetAttribLocation(shaderProgram, "color");
this->pOGLFunctions->glEnableVertexAttribArray(colAttrib);
this->pOGLFunctions->glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));

// Clear the screen to black
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);

// Draw a rectangle from the 2 triangles using 6 indices
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

//end test code

// Swap front/back buffers
this->pContext->swapBuffers( this );

@

I was using DX11 before swapping to OpenGL and I still feel a bit confused. I'm sure I'm doing something wrong, but can't find the problem: what I got is only the backgroundColor (I tested animating it also, and it works...)
The only clue I have is that if I look at my pContext pointer during execution, its qGLContextHandle is 0x0000...0.

Thanks!

alelink

Nevermind,
I found this working code and modified mine following it:
http://qt-project.org/wiki/Using-QOpenGLFunctions-and-QOpenGLContext

thanks anyway