Simple Example

To begin our introduction to gtkmm, we'll start with the simplest program possible. This program will create an empty 200 x 200 pixel window.

Source Code

File: base.cc (For use with gtkmm 4)

#include <gtkmm.h>

int main(int argc, char* argv[])
{
  auto app = Gtk::Application::create("org.gtkmm.examples.base");

  Gtk::Window window;
  window.set_default_size(200, 200);

  return app->run(window, argc, argv);
}

We will now explain each line of the example

#include <gtkmm.h>

All gtkmm programs must include certain gtkmm headers; gtkmm.h includes the entire gtkmm kit. This is usually not a good idea, because it includes a megabyte or so of headers, but for simple programs, it suffices.

The next statement:

auto app = Gtk::Application::create("org.gtkmm.examples.base");
creates a Gtk::Application object, stored in a Glib::RefPtr smartpointer. This is needed in all gtkmm applications. The create() method for this object initializes gtkmm.

The next two lines of code create a window and set its default (initial) size:

Gtk::Window window;
window.set_default_size(200, 200);

The last line shows the window and enters the gtkmm main processing loop, which will finish when the window is closed. Your main() function will then return with an appropriate success or error code. The argc and argv arguments, passed to your application on the command line, can be checked when run() is called, but this simple application does not use those arguments.

return app->run(window, argc, argv);

After putting the source code in simple.cc you can compile the above program with gcc using:

g++ simple.cc -o simple `pkg-config gtkmm-4.0 --cflags --libs`
Note that you must surround the pkg-config invocation with backquotes. Backquotes cause the shell to execute the command inside them, and to use the command's output as part of the command line. Note also that simple.cc must come before the pkg-config invocation on the command line.