Here is the idea:
I want to modofy a text document in different ways. Coloring it, changing color, resizing it... For that, I want to carry out each operation in a single window. So I want to create a function which will be responsible of opening the text document and preparing it before each above mentioned operation starts. For example, the gap between lines should be removed... In order to avoid opening the same file and proceding the preperation every time, I have decided to perform this step in a seperate window and just to call the function everytime I have to perform an operation, without rewriting the code again. That is the idea.
The real problem is to find and argument for the same function in another window when this function is called. That is the problem I have at the line 10 of second class.cpp

Any help would be welcome.