gtk/gtk.h: No file or directory found when compiling...

To do the checking, run this command

    $ pkg-config --cflags gtk+-2.0

If the output is something like this

    Package gtk+-2.0 was not found in the pkg-config search path.
    Perhaps you should add the directory containing `gtk+-2.0.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'gtk+-2.0' found

Install libgtk2.0-dev package

    $ sudo apt-get install libgtk2.0-dev