Working with gtkmm - A basic intro

I am not attempting to know everything about gtkmm or post an exhaustive tutorial on it. However if you would like to create a basic GUI in a relatively short period of time then you have come to the right place.

Here is a link to a more exhaustive tutorial (where I learned myself):Programming with gtkmm

Also visit this link which has detailed information on each class/namespace/file:
gtkmm 2.4 Documentation

Quick Introduction:

Abstract:
This tutorial covers how to create a GUI including one button arranged within a single frame. In another post I will eventually cover the basics of how to create a "more" section (i.e. hidden widgets). This is a very basic GUI that simply allows you to run commands depending on the callback of the button.

Idea:
The basic idea of gtkmm (GTK in general) is to create a gui where all elements are relative in position and size (for the most part). Each element is considered a widget and the things that hold it, containers. Elements are typically considered children, and containers parent(s).

Main.h
Add:

#include 
#include "gui.h"

Main.cpp
Add:

Gtk::Main kit(argc,argv);
gui gui;
Gtk::Main::run(gui);

gui.h
Add:

class gui : public Gtk::Window
{
public:
   gui();
   virtual ~gui();

protected:
 //Signal handlers:
 virtual void on_button_clicked();

//WINDOW - Child widgets
 Gtk::Frame window_frame;
 Gtk::VBox  window_box;
 Gtk::Button window_button,

gui.cpp
Add:

// Sets the Window Title
   set_title("Window Title");

// Sets the border width of the window
   set_border_width(10);

// Add the box to the window (the window can contain one widget/container)
   add(window_box);

// Add the frame to the box (boxes can contain multiple widgets/containers)
  window_box.pack_start(window_frame);

// Label the frame
  window_frame.set_label("Main");

// Add a button to the frame (frames can contain one widget/container)
  window_frame.add(button);

// This is how you do a call back (to a function where you define whatever you want)
  button.signal_clicked().connect(sigc::mem_fun(*this,
           &gui::on_button_clicked));

That's it. Just define your on_button_clicked() function and you are all set to make a simple GUI.