new FAQ entry: several Qt versions(was: Re: Ghost points in small app & question about using qt 2.0.1 libs.)

[Falk Brettschneider]

Jeremy Webster wrote:
>     One other question.  Now that I have all the qt 1.44 libs working, how
> do I make it so that I can also use the qt 2.0.1 libs?  I was going through
> some of the toots over at Qt and they seem to really like qvbox.h and some
> other things that apparently aren't in the 1.44 set.   I tried fiddling
> around in the Project Options menu with no success.  Is any of this
> documented anywhere?

Q: I want to develop with a newer Qt version than provided
   with my current Unix distribution. How do I do that?
A: Some things has to be done:
   1.) The newer Qt version must be installed parallely.
       [ For instance like this: /usr/lib/qt-1.44
                                 and
                                 /usr/lib/qt-2.0.2  ]
   2.) The compiler looks in /usr/local/qt or /usr/lib/qt 
       while deciding for the right headers of a Qt library.
       The link
          /usr/local/qt --> /usr/lib/qt
       is set in most of all cases.

       That's why you just need to set one of these links 
       to tell the compiler what to choose:
          /usr/lib/qt --> /usr/lib/qt-2.0.2
            (for compiling Qt2 programs)
          /usr/lib/qt --> /usr/lib/qt-1.44
            (for compiling Qt1.44 programs)

       The command for setting the link is:
          ln -s /usr/lib/qt /usr/lib/qt-2.0.2
       or
          ln -s /usr/lib/qt /usr/lib/qt-1.44

   3.) To make sure that the linker find the right lib simply 
       switch to user "root" and add two lines in /etc/ld.so.conf :
          /usr/lib/qt-2.0.2/lib
          /usr/lib/qt-1.44/lib
       and run:
          /sbin/ldconfig -v

-- 

Ciao,
--Falk