Extend INCLUDEPATH using pkg-config?

[Robert Hairgrove]

I am linking in GraphViz libraries to my project. I can add the libraries like this:

unix {
  CONFIG += link_pkgconfig
  PKGCONFIG += libgvc
}

This works OK. However, I am having problems with adding to the INCLUDEPATH variable. If I install GraphViz by building from the sources, the default include directory seems to be /usr/local/include/graphviz. However, if I install the graphviz-dev package from Ubuntu repositories, it puts it in /usr/include/graphviz. Therefore, I need to query pkg-config if I want to avoid hard-coding the include path to the header gvc.h.

Is there another way to use pkg-config in qmake to query the right include path?

[Robert Hairgrove]

Strange, after trying this again, it seems that the proper include path is now picked up as well as the libraries.

EDIT:
I might need to do this on Mac OSX as well ... if I install graphviz using MacPorts on OSX, how would I set up the .pro file to find the headers and libraries similar to the above?

[Robert Hairgrove]

Here is one solution for OSX which even uses GraphViz libraries:
https://github.com/nbergont/qgv/blob/master/QGVCore/GraphViz.pri

which I found after looking at this post on stackoverflow:
https://stackoverflow.com/questions/16972066/using-pkg-config-with-qt-creator-qmake-on-mac-osx

The key to this is to install graphviz using homebrew (and also installing pkg-config with homebrew), then in the .pro file it is necessary to add mac: QT_CONFIG -= no-pkg-config somewhere.

Note that there might be other issues such as setting the PATH environment variable to include /usr/local/bin if building with Qt Creator on OSX.

On Linux Ubuntu, it is sufficient to specify PKGCONFIG += libgvc instead of each library individually. This will output:

-lgvc -lcgraph -lcdt

I will have to test this on OSX if I ever need to actually build this application for that platform.