CMake and GTK+ 3: the easy way

If you look at my GitHub repositories you will notice that I’m a big fan of CMake and I use it in all my C projects.

Recently I started playing with GTK+ 3.0 but most of the official projects use the autotools toolchain, so there is little documentation on how to use CMake with GTK+.

But what is CMake and why should you care?
CMake is an open-source system for managing the build process using native building environments such as make.
I like it because it’s really easy to learn, at least compared to other build tools. It also produces a Makefile with a nice looking output.

Before we start

The sofware I’m using for this small guide is:

  • An up-to-date Fedora 17 (yep, I changed distro again. Sigh)
  • CMake version 2.8.8
  • GNU Make version 3.82
  • GTK+ 3.4.4

So if you encounter any problem RTFC (Read The Funny Changelog, of course).

Our sample and simple program

To demostrate how to use CMake we will use the classic GTK+ Hello World.

#include <gtk/gtk.h>
static void
activate(GtkApplication *app,
    gpointer user_data) {
    GtkWidget *window;
    window = gtk_application_window_new(app);
    gtk_window_set_title(GTK_WINDOW(window), "Hello GNOME");
    gtk_widget_show_all(window);
}
int
main(int argc, char **argv) {
    GtkApplication *app;
    int status;
    app = gtk_application_new("org.gtk.example",
        G_APPLICATION_FLAGS_NONE);
    g_signal_connect(app, "activate",
        G_CALLBACK(activate), NULL);
    status = g_application_run(G_APPLICATION(app), argc, argv);
    g_object_unref(app);
    return (status);
}

To compile it from the command line run:

$ gcc -o hello `pkg-config --libs --cflags gtk+-3.0` hello.c
$ ./hello

Enter CMake

The usual steps when using CMake are:

  1. Write a CMakeLists.txt file with the instruction on how to build your software
  2. Make a directory where you will build your software
  3. Run cmake
  4. Run make
  5. Congratulate yourself and use the time saved to troll people on the internet

This post, in an image

We start by writing our CMakeLists.txt file in the directory containing our source.

# Set the name and the supported language of the project
project(hello-world C)
# Set the minimum version of cmake required to build this project
cmake_minimum_required(VERSION 2.6)
# Use the package PkgConfig to detect GTK+ headers/library files
find_package(PkgConfig REQUIRED)
pkg_check_modules(GTK3 REQUIRED gtk+-3.0)
# Setup CMake to use GTK+, tell the compiler where to look for headers
# and to the linker where to look for libraries
include_directories(${GTK3_INCLUDE_DIRS})
link_directories(${GTK3_LIBRARY_DIRS})
# Add other flags to the compiler
add_definitions(${GTK3_CFLAGS_OTHER})
# Add an executable compiled from hello.c
add_executable(hello main.c)
# Link the target to the GTK+ libraries
target_link_libraries(hello ${GTK3_LIBRARIES})

Then we make the build folder

$ mkdir build
$ cd build

And we tell cmake to build the Makefile

$ cmake .. # Point cmake to the folder containing CMakeLists.txt

Finally we use make to build our program and we run it

$ make
$ ./hello

That’s it! I can’t tell you if this process works well for larger projects because I’m just getting started with GTK+ and CMake.
You should also check out some pre-made FindGTK3.cmake modules available, they may be better suited to your needs.

  • nn

    briljant, worked like a charm and out of the box

  • ib

    really good, works with qtcreator too.

  • Tom Nichols

    I've been looking all day for this. THANKS!!!

    Would love to see an explanation as to HOW you figured this out... eg

    • http://francesco-cek.com/ Francesco

      Hi,
      I simply looked at a couple of repositories online (don't remember which ones) and then with a bit of trial and error found the minimum steps necessary. It took me longer than you think to figure this out though.

  • Ronaldo Nascimento

    What if you use a src subdirectory to put all your .c source code files?

    • http://francesco-cek.com/ Francesco

      You need two CMakeLists.txt files, one in the root directory, one the source directory. Look at this link to see an example (the whole page is worth reading). Basically, you need to use the same CMakeLists.txt as in this example in the root directory, but replacing the `add_executable` and `target_link_libraries` with `add_subdirectory`. Then in the CMakeLists.txt file in the source file you use `add_executable` and `target_link_libraries`.

  • John Doe

    Just wanted to say thank you for probably saving me a lot of time 🙂

  • Rautaputki

    Thank you. Your example was all I needed to get started.

  • Dariusz Karolewski

    Very good now i can build tree open cv-gtk