Strange Behavior with QGLWidget if Fullscreen

**Barry79** · 3rd April 2009, 16:18

Hi,

I have the following very simple class -

Qt Code:

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#ifndef GLTEST_H_
#define GLTEST_H_
 
#include <QtGui>
#include <GL/glew.h>
#include <QGLWidget>
#include <iostream>
 
using namespace std;
 
 class GlTest : public QGLWidget
  {
 
  public:
    Q_OBJECT
 
  public:
 
	  GlTest(){}
 
	  virtual void initWindow(){}
 
	  virtual void initializeGL()
	  {
		  QGLWidget::initializeGL();
	  }
 
	  virtual void paintGL()
	  {
		  cout << "paintGL"<< endl;
		  QGLWidget::paintGL();
	  }
 
	  virtual void swapBuffers()
	  {
	  	QGLWidget::swapBuffers();
	  }
};

#ifndef GLTEST_H_
#define GLTEST_H_

#include <QtGui>
#include <GL/glew.h>
#include <QGLWidget>
#include <iostream>

using namespace std;

 class GlTest : public QGLWidget
  {

  public:
    Q_OBJECT

  public:

	  GlTest(){}

	  virtual void initWindow(){}

	  virtual void initializeGL()
	  {
		  QGLWidget::initializeGL();
	  }

	  virtual void paintGL()
	  {
		  cout << "paintGL"<< endl;
		  QGLWidget::paintGL();
	  }

	  virtual void swapBuffers()
	  {
	  	QGLWidget::swapBuffers();
	  }
};

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which I call via -

Qt Code:

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if(!glWindow.get())
  glWindow.reset(new GlTest());
 
glWindow->showFullScreen();

if(!glWindow.get())
  glWindow.reset(new GlTest());

glWindow->showFullScreen();

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I'm using two screens so the above code will fill the first screen with the gl window. If I then click on another application in the second window, the above program prints - "paintGL". Then, when I click on the gl window again, this message is again printed. However if I use show() instead of showFullScreen() then this behavior does not happen. In other words, I can click on other windows and the paintGL() function is not entered - as expected. Why might this difference between show() and showFullScreen() be? If this is a bug what might a work around be? I don't wish for paintGL() to be called when the gl window stops being active (or when it starts being active again for that matter). I wish it to work as it does with show().

The above code is a very stripped down version of what I am actually doing. At the moment I am having problems when in full screen mode because the scene I wish to show in the gl window is being recalculated each time paintGL() is being called.

Any tips?

Barry.