One QGLWidget that manage QGLWidget childs

Hi.

I would like to know if the following use case is supported by QT.

I have one “Parent” QGLWidget :

Code:

---

class ParentGLWidget : public QGLWidget 
    {
    ...
        ParentGLWidget(QGLContext * context, QWidget *parent = 0) : QGLWidget(context, parent) {... }
    ...
        void initializeGL()
        {
        qglClearColor(qtPurple.dark());
        glEnable(GL_CULL_FACE);
        ...
        }
 
        void paintGL()
        {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        }
 
        void resizeGL(int width, int height)
        {
        glViewport((width - side) / 2, (height - side) / 2, side, side);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrthof(-0.5, +0.5, -0.5, +0.5, 4.0, 15.0);
        glMatrixMode(GL_MODELVIEW);
        }
    }

---

There are other “childs" GLWidget that should be drawn "inside" the parent widget context :

Code:

---

class ChildGLWidget : public QGLWidget 
    {
    ...
        ChildGLWidget(QGLContext * context, QWidget *parent = 0) : QGLWidget(context, parent) {... }
    ...
        void initializeGL()
        {
         // optional
         // at least, should not overwrite what have been done in the top level widget
        }
 
        void paintGL()
        {
        glLoadIdentity();
        glTranslatef(0.0, 0.0, -10.0);
        glRotatef(xRot, 1.0, 0.0, 0.0);
        // draw some object in the gl world
        }
 
        void resizeGL(int width, int height)
        {
         // optional
         // at least, should not overwrite what have been done in the top level widget
        }
    }

---

I would like to use them like this :

Code:

---

QGLContext * context = new QGLContext(QGLFormat(QGL::SampleBuffers));
ParentGLWidget * parent = new ParentGLWidget(context);
ChildGLWidget * child_1 = new ChildGLWidget(context, parent);
ChildGLWidget * child_2 = new ChildGLWidget(context, parent);

---

The childs could be managed (drawing, deletion, …) by the parent (like traditional widgets do), and I would be able to have some part of 3D rendering in "modules".

I haven’t been able to run such a use case.

Is there any design flaw in this use case ? Do you think there are others ways to do that ?

Thank for your help.

Traditional widgets are not managed by their parent in any way. Sharing GL contexts makes it possible to share textures and display lists.

Thank you for your reply.

I thought that the parent widget recursively triggered the display of its childs... So i thought that i would be possible to call the InitializeGL, paintGL, and resizeGL methods of the childs by a parent.

Actualy i have a class that contains a list of object with GL drawing methods that are called inside the paintGL method of an unique QGLWidget. I wondered if it was a good design.

Regards.

Paul.

Quote:

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Originally Posted by polch

I thought that the parent widget recursively triggered the display of its childs...

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No. The parent paints itself on a given canvas and then each of its children paints itself on the same (or different) canvas. Then everything is assembled and rendered to the screen.

Quote:

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So i thought that i would be possible to call the InitializeGL, paintGL, and resizeGL methods of the childs by a parent.

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I don't think stacking GL widgets onto each other would do you any good.

Quote:

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Actualy i have a class that contains a list of object with GL drawing methods that are called inside the paintGL method of an unique QGLWidget. I wondered if it was a good design.

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Seems ok. Just call them from the GL widget's paintGL() implementation and you're done. No need for any extra widgets.

Quote:

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Seems ok. Just call them from the GL widget's paintGL() implementation and you're done. No need for any extra widgets.

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That what i actually do.

Thank you for the discussion.