QGLwidget pops out from qmainwindow even if it's the mainwindow.ui - c++

Question

i have a MainWindow which displays some plots that come from widget promotion. Now i have decided that i want to embed a QGLWidget so that i can draw a 3D image near them.
I created a QGLWidget inside the creator design and i have promoted it to MyGLWidget class
MyGLWidget.h
#ifndef MYGLWIDGET
#define MYGLWIDGET
#include <QtOpenGL>
#include <QGLWidget>
#include <array>
class MyGLWidget : public QGLWidget{
Q_OBJECT // must include this if you use Qt signals/slots
public:
explicit MyGLWidget(QWidget *parent = 0);
std::array<GLfloat, 3> angles;
protected:
// Set up the rendering context, define display lists etc.:
void initializeGL();
// draw the scene:
void paintGL();
// setup viewport, projection etc.:
void resizeGL (int width, int height);
};
#endif // MYGLWIDGET
MyGLWidget.cpp
#include "myglwidget.h"
#include <gl/GLU.h>
#include <iostream>
MyGLWidget::MyGLWidget(QWidget *parent){
angles[0] = 50.0;
angles[1] = 15.0;
}
/*
* Sets up the OpenGL rendering context, defines display lists, etc.
* Gets called once before the first time resizeGL() or paintGL() is called.
*/
void MyGLWidget::initializeGL(){
//activate the depth buffer
glEnable(GL_DEPTH_TEST);
}
/*
* Sets up the OpenGL viewport, projection, etc. Gets called whenever the widget has been resized
* (and also when it is shown for the first time because all newly created widgets get a resize event automatically).
*/
void MyGLWidget::resizeGL (int width, int height){
glViewport( 0, 0, (GLint)width, (GLint)height );
/* create viewing cone with near and far clipping planes */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 30.0);
glMatrixMode( GL_MODELVIEW );
}
/*
* Renders the OpenGL scene. Gets called whenever the widget needs to be updated.
*/
void MyGLWidget::paintGL(){
//delete color and depth buffer
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0f,0.0f,-20.0f); //move along z-axis
glRotatef(angles[0],0.0,1.0,0.0); //rotate 30 degress around y-axis
glRotatef(angles[1],1.0,0.0,0.0); //rotate 15 degress around x-axis
/* create 3D-Cube */
glBegin(GL_QUADS);
//front
glColor3f(1.0,0.0,0.0);
glVertex3f(1.0,1.0,1.0);
glVertex3f(-1.0,1.0,1.0);
glVertex3f(-1.0,-1.0,1.0);
glVertex3f(1.0,-1.0,1.0);
//back
glColor3f(0.0,1.0,0.0);
glVertex3f(1.0,1.0,-1.0);
glVertex3f(-1.0,1.0,-1.0);
glVertex3f(-1.0,-1.0,-1.0);
glVertex3f(1.0,-1.0,-1.0);
//top
glColor3f(0.0,0.0,1.0);
glVertex3f(-1.0,1.0,1.0);
glVertex3f(1.0,1.0,1.0);
glVertex3f(1.0,1.0,-1.0);
glVertex3f(-1.0,1.0,-1.0);
//bottom
glColor3f(0.0,1.0,1.0);
glVertex3f(1.0,-1.0,1.0);
glVertex3f(1.0,-1.0,-1.0);
glVertex3f(-1.0,-1.0,-1.0);
glVertex3f(-1.0,-1.0,1.0);
//right
glColor3f(1.0,0.0,1.0);
glVertex3f(1.0,1.0,1.0);
glVertex3f(1.0,-1.0,1.0);
glVertex3f(1.0,-1.0,-1.0);
glVertex3f(1.0,1.0,-1.0);
//left
glColor3f(1.0,1.0,0.0);
glVertex3f(-1.0,1.0,1.0);
glVertex3f(-1.0,-1.0,1.0);
glVertex3f(-1.0,-1.0,-1.0);
glVertex3f(-1.0,1.0,-1.0);
glEnd();
}
Now in the constructor of mainwindow.cpp i call ui->wgl->show(); where wgl is the ObjectName of the widget promoted to my class.
The cube is rendered but the widget pops out from the mainwindow instead of stay where i designed it

Answer 1

Your widget has no parent, but in Qt widget without parent is a separate window, so try to do this in constructor.
MyGLWidget::MyGLWidget(QWidget *parent) : QGLWidget(parent)
{
angles[0] = 50.0;
angles[1] = 15.0;
}
If you really use Qt Designer, then you have ui->setupUi(this); in your code. It does something like this (allocate memory and set parent):
MyGLWidget *wgl = new MyGLWidget(this);
It passes this as parent, but your current MyGLWidget take it but ignores it. So with code in my answer all should be fine.