Table of Contents
Labels are the main method of placing non-editable text in windows, for instance to place a title next to a Entry widget. You can specify the text in the constructor, or with the set_text() method.
The width of the label will be adjusted automatically. You can produce multi-line labels by putting line breaks ("\n") in the label string.
The label text can be justified using the set_justify() method. The widget is also capable of word-wrapping - this can be activated with set_line_wrap().
TODO: gtkmm2: markup.
Below is a short example to illustrate these functions. This example makes use of the Frame widget to better demonstrate the label styles. (The Frame widget is explained in the Frame section.)
File: examplewindow.h
#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H
#include <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();
protected:
  //Child widgets:
  Gtk::HBox m_HBox;
  Gtk::VBox m_VBox, m_VBox2;
  Gtk::Frame m_Frame_Normal, m_Frame_Multi, m_Frame_Left, m_Frame_Right,
    m_Frame_LineWrapped, m_Frame_FilledWrapped, m_Frame_Underlined;
  Gtk::Label m_Label_Normal, m_Label_Multi, m_Label_Left, m_Label_Right,
    m_Label_LineWrapped, m_Label_FilledWrapped, m_Label_Underlined;
};
#endif //GTKMM_EXAMPLEWINDOW_H
File: examplewindow.cc
#include "examplewindow.h"
#include <iostream>
ExampleWindow::ExampleWindow()
:
  m_HBox(false, 5),
  m_VBox(false, 5),
  m_Frame_Normal("Normal Label"),
  m_Frame_Multi("Multi-line Label"),
  m_Frame_Left("Left Justified Label"),
  m_Frame_Right("Right Justified Label"),
  m_Frame_LineWrapped("Line wrapped label"),
  m_Frame_FilledWrapped("Filled, wrapped label"),
  m_Frame_Underlined("Underlined label"),
  m_Label_Normal("_This is a Normal label", true),
  m_Label_Multi("This is a Multi-line label.\nSecond line\nThird line"),
  m_Label_Left("This is a Left-Justified\nMulti-line label.\nThird line"),
  m_Label_Right("This is a Right-Justified\nMulti-line label.\nFourth line, (j/k)"),
  m_Label_Underlined("This label is underlined!\nThis one is underlined in quite a funky fashion")
{
  set_title("Label");
  set_border_width(5);
  add(m_HBox);
  m_HBox.pack_start(m_VBox, Gtk::PACK_SHRINK);
  m_Frame_Normal.add(m_Label_Normal);
  m_VBox.pack_start(m_Frame_Normal, Gtk::PACK_SHRINK);
  m_Frame_Multi.add(m_Label_Multi);
  m_VBox.pack_start(m_Frame_Multi, Gtk::PACK_SHRINK);
  m_Label_Left.set_justify(Gtk::JUSTIFY_LEFT);
  m_Frame_Left.add(m_Label_Left);
  m_VBox.pack_start(m_Frame_Left, Gtk::PACK_SHRINK);
  m_Label_Right.set_justify(Gtk::JUSTIFY_RIGHT);
  m_Frame_Right.add(m_Label_Right);
  m_VBox.pack_start(m_Frame_Right, Gtk::PACK_SHRINK);
  m_HBox.pack_start(m_VBox2, Gtk::PACK_SHRINK);
  m_Label_LineWrapped.set_text("This is an example of a line-wrapped label.  It " \
    "should not be taking up the entire             " /* big space to test spacing */\
    "width allocated to it, but automatically " \
    "wraps the words to fit.  " \
    "The time has come, for all good men, to come to " \
    "the aid of their party.  " \
    "The sixth sheik's six sheep's sick.\n" \
    "     It supports multiple paragraphs correctly, " \
    "and  correctly   adds "\
    "many          extra  spaces. ");
  m_Label_LineWrapped.set_line_wrap();
  m_Frame_LineWrapped.add(m_Label_LineWrapped);
  m_VBox2.pack_start(m_Frame_LineWrapped, Gtk::PACK_SHRINK);
  m_Label_FilledWrapped.set_text("This is an example of a line-wrapped, filled label.  " \
    "It should be taking " \
    "up the entire              width allocated to it.  " \
    "Here is a sentence to prove "\
    "my point.  Here is another sentence. "\
    "Here comes the sun, do de do de do.\n"\
    "    This is a new paragraph.\n"\
    "    This is another newer, longer, better " \
    "paragraph.  It is coming to an end, "\
    "unfortunately.");
  m_Label_FilledWrapped.set_justify(Gtk::JUSTIFY_FILL);
  m_Label_FilledWrapped.set_line_wrap();
  m_Frame_FilledWrapped.add(m_Label_FilledWrapped);
  m_VBox2.pack_start(m_Frame_FilledWrapped, Gtk::PACK_SHRINK);
  m_Label_Underlined.set_justify(Gtk::JUSTIFY_LEFT);
  m_Label_Underlined.set_pattern ("_________________________ _ _________ _ ______     __ _______ ___");
  m_Frame_Underlined.add(m_Label_Underlined);
  m_VBox2.pack_start(m_Frame_Underlined, Gtk::PACK_SHRINK);
  show_all_children();
}
ExampleWindow::~ExampleWindow()
{
}
File: main.cc
#include <gtkmm/main.h>
#include "examplewindow.h"
int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);
  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.
  return 0;
}