File: examplewindow.h
#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H
#include <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();
protected:
  virtual void fill_buffers();
  
  //Signal handlers:
  virtual void on_button_quit();
  virtual void on_button_buffer1();
  virtual void on_button_buffer2();
  //Child widgets:
  Gtk::VBox m_VBox;
  Gtk::ScrolledWindow m_ScrolledWindow;
  Gtk::TextView m_TextView;
  
  Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer1, m_refTextBuffer2;
  Gtk::HButtonBox m_ButtonBox;
  Gtk::Button m_Button_Quit, m_Button_Buffer1, m_Button_Buffer2;
};
#endif //GTKMM_EXAMPLEWINDOW_H
File: examplewindow.cc
#include "examplewindow.h"
ExampleWindow::ExampleWindow()
: m_Button_Quit(Gtk::Stock::QUIT),
  m_Button_Buffer1("Use buffer 1"),
  m_Button_Buffer2("Use buffer 2")
{
  set_title("Gtk::TextView example");
  set_border_width(5);
  set_default_size(400, 200);
  add(m_VBox);
  //Add the TreeView, inside a ScrolledWindow, with the button underneath:
  m_ScrolledWindow.add(m_TextView);
  //Only show the scrollbars when they are necessary:
  m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);
  m_VBox.pack_start(m_ScrolledWindow);
  //Add buttons:
  m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
  m_ButtonBox.pack_start(m_Button_Buffer1, Gtk::PACK_SHRINK);
  m_ButtonBox.pack_start(m_Button_Buffer2, Gtk::PACK_SHRINK);
  m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
  m_ButtonBox.set_border_width(5);
  m_ButtonBox.set_spacing(5);
  m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
  //Connect signals:
  m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_quit) );
  m_Button_Buffer1.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_buffer1) );
  m_Button_Buffer2.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_buffer2) );
  fill_buffers();
  on_button_buffer1();
  show_all_children();
}
void ExampleWindow::fill_buffers()
{
  m_refTextBuffer1 = Gtk::TextBuffer::create();
  m_refTextBuffer1->set_text("This is the text from TextBuffer #1.");
  m_refTextBuffer2 = Gtk::TextBuffer::create();
  m_refTextBuffer2->set_text(
          "This is some alternative text, from TextBuffer #2.");
}
ExampleWindow::~ExampleWindow()
{
}
void ExampleWindow::on_button_quit()
{
  hide();
}
void ExampleWindow::on_button_buffer1()
{
  m_TextView.set_buffer(m_refTextBuffer1);
}
void ExampleWindow::on_button_buffer2()
{
  m_TextView.set_buffer(m_refTextBuffer2);
}
File: main.cc
#include <gtkmm/main.h>
#include "examplewindow.h"
int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);
  ExampleWindow window;
  //Shows the window and returns when it is closed.
  Gtk::Main::run(window);
  return 0;
}