Multi-Platform - What to use? Where to learn?

Hello,
I'm mostly programming in PHP and C#, but I have some experience (pretty basic) in C++. The most "complicated" thing I created was a window with some buttons and lists on it (using Win32 API), and playing with classes.
Now, I want to get deeper into C++ - creating multi-platfrom (Windows, Linux, or even Mac if that is possible).
When I want to open a file I can use Win32 API, but now, do I have to write the same code 2/3 times (for each OS)? And what about the GUI? What can I use and what not? Which IDE to use?
Can anyone give me an online website or anything that can help me begin?

Thanks,
Ori Lahav.

If you stay with standard C++ functions, and do NOT use any Win32 API calls, you can easily write portable code for files and such. There are various GUI libraries (WxWidgets comes to mind) that are available for most platforms.

My real world experience has been that there is some functionallity that is best written using OS specific calls. In these cases, I have created a custom set of libraries that expose a unified interface. Now when I write an application, I simple call MY libraries. Depending on which OS I am targeting, I simply link against a different library.

The cross-platform GUI toolkit I've had the most experience with is GTK+. However, for some reason WxWidgets seems to get pushed a bit more around here, so maybe that might be worth checking out too.

Another alternative is Qt (http://trolltech.com). I use it since its first release. However, to make it REALLY work on every platform and ARCHITECTURE, you need to know a little about makefiles, and stuff.
It's free for *NIX systems. Under Windows you need to compile with "minGW" (gcc clone for Windows). As for an IDE, I use anaconda in *NIX (KDevelop is probably the better alternative). Since I BOUGHT Qt, I can use it (Windows) with VS. If you obtain the open edition, try dev-c++.

Quote:

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Originally Posted by Lindley

The cross-platform GUI toolkit I've had the most experience with is GTK+. However, for some reason WxWidgets seems to get pushed a bit more around here, so maybe that might be worth checking out too.

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To a large degree it is a matter of preference, and what you are familiar with. People with MFC backgrounds seem to prefer WxWidgets. People with a Tk/Tcl (also a viable alternative) seem to prefer GTK+.

For most people I recommend spending some time (more than just a few hours....) with each one of them.

Thank you very much!
I coded wxWidgets and compiled (using wxDev C++ in Windows), switched to Linux, downloaded the packages and compiled for Linux.
Making cross-platform GUI in C++ is so easy!

About files location. In Windows I placed all the config and data files in the same folder as the program. Is it should be like this in Linux and Mac?

Thanks again,
Ori Lahav.