I am trying to make a software using QT to measure the FPS of a specific area of the screen. The software is as follows: a main window with a button and label to display the current FPS and average, an overlay window that will represents the area where the measurement will be done.

When the software is launched the two windows appear. The user can change the area where he want to measure the FPS by moving and resizing the overlay window then clicks the button to start.

This is the mission i have been given: Design a cross-platform (windows and macos) Frames Per Seconds measurement tool in an OpenGL context (Qt).

I am trying to use QOpenGLWidget to get the QImage of the area covered by the overlay window but i can’t understand how i am going to get the frame per second from this.

I’ve seen some similiar problems but they usually want the fps of the QT application while what i want is the fps of the whole area covered by the overlaywindow

How to do so? Is there anyone who has an idea on where to start?