How can I get a 30 or 60 frame rate when using QGLWidget? QTimer is not acurate

[ricardo]

Hi friends!

I think I found a way. just a WHILE(1) and use qApp->processEvents() to avoid a blocked UI. This code is executed when PLAY is pressed. There are no timers.

// simulate it for 10 seconds
				m_rendered_frames=0;
				m_time.start();
				while (m_time.elapsed()<=10000) {
					QTime now;
					now.start();
					qApp->processEvents();
  					m_current_level->Update(0);
					m_gl_drawer->updateGL();
					m_rendered_frames++;
					// sleep a while
					if (SIMULATION_UPDATE_INTERVAL_IN_MS-now.elapsed()>0) {
						QTest::qSleep(SIMULATION_UPDATE_INTERVAL_IN_MS-now.elapsed());
					} 
				}
				// info
				float fps=m_rendered_frames/10.0;
				QString m=QString("FPS: %1. rendered frames: %2. Timer interval (ms): %3.").arg(fps).arg(m_rendered_frames).arg(SIMULATION_UPDATE_INTERVAL_IN_MS);
				QMessageBox::warning(this, "Warning", m);

// simulate it for 10 seconds
				m_rendered_frames=0;
				m_time.start();
				while (m_time.elapsed()<=10000) {
					QTime now;
					now.start();
					qApp->processEvents();
  					m_current_level->Update(0);
					m_gl_drawer->updateGL();
					m_rendered_frames++;
					// sleep a while
					if (SIMULATION_UPDATE_INTERVAL_IN_MS-now.elapsed()>0) {
						QTest::qSleep(SIMULATION_UPDATE_INTERVAL_IN_MS-now.elapsed());
					} 
				}
				// info
				float fps=m_rendered_frames/10.0;
				QString m=QString("FPS: %1. rendered frames: %2. Timer interval (ms): %3.").arg(fps).arg(m_rendered_frames).arg(SIMULATION_UPDATE_INTERVAL_IN_MS);
				QMessageBox::warning(this, "Warning", m);

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It works properly. What do you think?

[wysota]

Event processing is sparse, keys might not be responding or might respond with a delay. That's not a good way to do it. But if it suits your needs...