I am going to do my best explaining the problem at hand:

I am trying to develop existing code. When the program finishes loading there are two widgets on the screen, one that I dont care about and can simple cancel from the screen and the other that I am concered about. Basically my goal is to press a button (play button) and data will be read from a text file, placed into memory, and then the widget on the screen will be repainted, displaying the changes. This process will be repeated over and over again until a button like stop is pressed. That's the idea of the program.
So far, I have created a QPlayback .h and .cpp files to work with the overall program. In my MainWindow .cpp 's constructor, I called the "new" operator to create the button that is a play button. In the contructor for the QPlayback .h, I want to connect the buttons clicked( ) from 'this' to the repaint of the widget on the screen.
My confusion is this: first, I do not know which object to use in the connect function to allow the button, the playbutton that is, to take control of the widget. I have read some other posts and I am confused with this process of repaint( ) and update( ). Please do help further ? Given the above scenario, how would I develop such a button, what should I keep in mind when developing play, fast-forward, pause, stop, like a tape player...