QOpenGLWidget just works correctly in the first paint - c++

Question

I developed a simple Point Cloud Data viewer (just for learning) and I am using Qt Library. My first implementation used QOpenGLWindow but now I want to use a QOpenGLWidget to uses it such as dynamic library.
Regarding QOpenGLWidget, it just works in the first "painting" (call to PaintGL when I create the widget) and nothing happens on successive paintGL() calls. This problem does not appear in QOpenGLWindow, it works perfectly.
My PaintGL() paint using the next method of my class:
void AEOpenGLViewer::renderGL() {
// Clear
glClear(GL_COLOR_BUFFER_BIT);
shader_program->bind();
shader_program->setUniformValue(u_worldToCamera, camera.toMatrix());
shader_program->setUniformValue(u_cameraToView, projection);
{
for (size_t globjects_index = 0; globjects_index < objects.size(); ++globjects_index) {
objects.at(globjects_index).vao->bind();
shader_program->setUniformValue(u_modelToWorld, objects.at(globjects_index).transform.toMatrix());
glDrawArrays(objects.at(globjects_index).primitive_type, 0, objects.at(globjects_index).vertices.size());
objects.at(globjects_index).vao->release();
}
}
shader_program->release();
}
where "objects" is a std::vector of a local struct that define an OpenGL's object in my applicacion:
typedef struct {
QOpenGLBuffer *vbo;
QOpenGLVertexArrayObject *vao;
GLenum primitive_type;
std::vector<Vertex> vertices;
Transform3D transform;
} GLObject;
The slot "update()" is called using input events (KeyPressEvent, MouseMoveEvent..) just in order to reduce the GPU load.
In case someone is interested, the vbo is allocated as follow:
void AEOpenGLViewer::prepareObjectInGPU(GLObject globject) {
shader_program->bind();
{
// Create Buffer (Do not release until VAO is created) (vbo)
globject.vbo->create();
globject.vbo->bind();
globject.vbo->setUsagePattern(QOpenGLBuffer::StaticDraw);
globject.vbo->allocate(globject.vertices.data(), globject.vertices.size() * sizeof(Vertex));
// Create Vertex Array Object (vao)
globject.vao->create();
globject.vao->bind();
shader_program->enableAttributeArray(0);
shader_program->enableAttributeArray(1);
shader_program->setAttributeBuffer(0, GL_FLOAT, Vertex::positionOffset(), Vertex::PositionTupleSize, Vertex::stride());
shader_program->setAttributeBuffer(1, GL_FLOAT, Vertex::colorOffset(), Vertex::ColorTupleSize, Vertex::stride());
// Release (unbind) all
globject.vbo->release();
globject.vao->release();
}
shader_program->release();
}

Answer 1

The problem is solved, It happened because I have to make the corresponding context current during the allocation of the object in the GPU (my prepareObjectInGPU() method). So, the problem is solved as follow:
void AEOpenGLViewer::prepareObjectInGPU(GLObject globject) {
makeCurrent();
shader_program->bind();
{
...
}
shader_program->release();
doneCurrent();
}
In the QOpenGLWindow, it was not necessary but I recommended to do it as good practices. Remember, during the PaintGL() It is not necessary to call the makeCurrent() because it is called automatically before invoking paintGL().
However, if someone want to answer me then you are welcome.
Thanks!