Some questions about a CAD software based on QCAD resource

I'm a freshman in Qt,but currently I have some tasks about develop a small CAD software under Linux OS by myself.This CAD only has some simple functions like opening a DXF format file, edit the opened file, draw some circles and lines on it, mirror, cut and delete features on the drawing and some other basic functions.

I think that to develop the whole software by coding myself is too difficult to me. So i decided to do the work by using the QCAD's resource code.For example, I can use it's some existing classes and functions or lib. I hope I can add them into my own CAD.

I have downloaded the resource code from RibbonSoft's website. But I cannot figure out how and where to start my work. Too many files and too many codes. I was totally messed up.

I hope someone can show me a guideline to help me begin my work and tell me the major method about where to start. And what kind of knowledge is needed to complete this tiny simple CAD?

Thanks a lot!Every informations are welcome.Thanks again!

Welcome to the real world! :p

The best place to start is main(). If there is a QApplication subclass, look at it. Then at the top level widgets. Work your way down from there. Your goal is to find out how everything works together (in a general sense). Then you will know how to find the details you need for specific parts of the application.

Thank you very much. Though it is very difficult to me, but i will try my best to complete this work.
If there are some problems when i do this work, I will post on the forum to discuss with you guys.
Thanks again.

You asked for it, so here goes.

Why do u want to write a CAD program?
Are you directing to a special need?
Are you just trying to learn Qt programming.?
Have you any experience with CAD?
Are you sure you aren't talking about modeling?

Enough of this stuff.

I'm a structural engineer involved in the precast concrete industry and have used many different CAD systems dating back to before Microsoft. I am currently writing a vertically integrated, parametrically driven CAD program using Qt and OpenGL myself

You are on the right track with Qcad.
Take a look VariCAD. This what you don't want to do.
Keep the user interface simple.

You should bare in mind that a compter program, other than a game, is only a means to an end, not an end in its self.

If you would like to discuss this with me, send me an e-mail.