It is normal in GUI, where we will set an Input Widget (Scrollbar, slider, textedit, etc) and will be controlled/ displayed to the Output Widget (ProgressBar, LCD, Label)

Can I control the Output widget instead of using the Input widget, but I'm using a predefined text inside a textfile (.txt) which will be loaded inside the QT?

Example:

I open the notepad, type in '60' , save as ".txt" file and execute my QT program. As it launches, the progress bar inside the window will move to "60", or the LCD will display "60".

Can anyone teach me how to do that?

Thanks