Question

can i write my own c++ gui library ?? how to proceed in that way ?

Answer 1

basically you can, but if you go and look how GTK+ and Qt has been written you'll see that is is huge amount of work. I suggest to before you start writing your own you to learn how to use one already existing GUI lib, preferably open source, so you can see source code.

Answer 2

Writing your own GUI is like writing your sort algorithm; its a useful exercise if you're learning the ropes of a language, but an utter wise of time otherwise. No point in writing code that has already been written. Look some of them up; they're already complected enough without having to write them from scratch.