QGLWidget and QGraphicsScene Program Crash

cazador7907

I've been experimenting with rendering a QGLWidget within a QGraphicsScene. The program compiles just fine. However, when I attempt to render some text to the middle of the widget, the program will run for about a second and then it crashes. I've narrowed the problem down to the paintGL method (code below). However, I can't figure out why it's crashing.

//Main
@
QGraphicsScene scene;
scene.setSceneRect(0,0, 800, 600);
scene.setItemIndexMethod(QGraphicsScene::NoIndex);
scene.addWidget(new BackGroundGLWidget());

QGraphicsView view(&scene);
view.setMaximumSize(800, 600);
view.setAlignment(Qt::AlignCenter);
view.showMaximized();
view.show();

@

PaintGL Code
@
// Clear screen and depth buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glLoadIdentity(); // Reset view matrix
glTranslatef(0.0f, 0.0f, -1.0f); // Move into screen 1 unit

// Pulsing colors based on text position
glColor3f(qMax(0.0, 1.0f * cos(cnt1)),
          qMax(0.0, 1.0 * sin(cnt2)),
          qMin(1.0, 1.0f - 0.5f * cos(cnt1 + cnt2)));

// Print text on the screen
QFont font;
font.setBold(true);
font.setPixelSize(18);

// Print some text without taking the transformation into account
// Very useful class to align some text in OpenGL at the absolute
// borders of the screen!
QFontMetrics metrics(font);
QString bottomRightText("I am always at the bottom right.");
renderText((width() - metrics.width(bottomRightText) - 10)/2,
           (height() - metrics.height() + 10)/2, bottomRightText, font);

@

Franzk

renderText is buggy at best (and about to be obsoleted). Try removing that call and see whether it crashes...

dangelog

You can't put a QGLWidget inside a QGraphicsScene because it paints on screen.

cazador7907

So, how would I set a jpg image as overlay dialogs, buttons, lines and the like?

Laurence -

Franzk

Hm, you should do setViewport(new QGLWidget) on your graphics view. That enables you to do opengl stuff in your scene.

dangelog

[quote author="cazador7907" date="1296309277"]
So, how would I set a jpg image as overlay dialogs, buttons, lines and the like?

Laurence -

[/quote]

I'm not getting it... do you have all of that in a QGraphicsScene or as ordinary widgets? Where and how is OpenGL involved in this?