Checking prerequisites for building Qt from source

Question

The Qt website lists some packages, which need to be installed to build Qt:

http://qt-project.org/doc/qt-4.8/requirements-x11.html

Are they all necessary?

How do I check which one are already installed?

Answer 1

As you noted the Qt website lists out packages that need to be installed for various operating systems. As you noted the x11, I assume you're using some flavor of Linux.

For Ubuntu, if you want to check if a package is already installed you can do this from the terminal:

sudo apt-cache policy libxtst-dev

libxtst-dev:
Installed: (none)
Candidate: 2:1.2.0-4ubuntu0.1
Version table:
  2:1.2.0-4ubuntu0.1 0

That shows us libxtst-dev is not currently installed (this is a Qt package for embedded Linux development to get the framebuffer working)

Then you can install it via:

sudo apt-get install libxtst-dev

Then you can check the cache policy again to see what it looks like if you do have the package installed:

$ sudo apt-cache policy libxtst-dev
libxtst-dev:
  Installed: 2:1.2.0-4ubuntu0.1
  Candidate: 2:1.2.0-4ubuntu0.1
  Version table:
*** 2:1.2.0-4ubuntu0.1 0

Note: it's not really needed to check if the packages are installed first because if you just try to install them the installation program will tell you if it's already present by a message like:

libxtst-dev is already the newest version.

---

If you have a Suse type box you can use a different command such as:

rpm -qa | grep -i <a small substring of the name of software>

So something like:

rpm -qa | grep -i libxtst

will tell you if it's installed or not. Then you can use Yast to install it if required.

---

Now for your question: "Are they all necessary?"

That depends on what you're trying to do/build. Do you want to build Qt from source, or do you just want to use an API like qt creator?

The page you linked to actually tells you some information about what is required:

The QtGui module and the QtCore module, which provides the non-GUI features required by QtGui, depend on the libraries described in the following table.

So, if you want a user interface (and of course you do if you're using Qt) then you need all the packages listed in the table.

To build Qt from its source code, you will also need to install the development packages for these libraries for your system.

And if you're using Qt creator (or some SDK with precompiled Qt libs) you won't need to build from source, so you don't need the list of xxx-dev packages.