5. Label

Labels are used to display non-editable text in widgets.You can provide special text type setting markup, also specify selectable & unselectable texts. There are some examples below:

#!/usr/bin/ruby
require "gtk3"

win = Gtk::Window.new
# set window title
win.set_title("Label Example")
multi_line = %{This is an example of a line-wrapped label.  It
                should not be taking up the entire      
                width allocated to it, but automatically 
                     It supports multiple paragraphs correctly, 
                and  correctly   adds 
                many          extra  spaces. }
hbox = Gtk::Box.new(:horizontal, 10)
hbox.set_homogeneous(false)

vbox_left = Gtk::Box.new(:vertical, 10)
vbox_left.set_homogeneous(false)
vbox_right = Gtk::Box.new(:vertical, 10)
vbox_right.set_homogeneous(false)
hbox.pack_start(vbox_left, :expand => true, :fill => true, :padding => 0)
hbox.pack_start(vbox_right, :expand => true, :fill => true, :padding => 0)

# simple label
label = Gtk::Label.new("This is a normal label")
vbox_left.pack_start(label, :expand => true, :fill => true, :padding => 0)

label = Gtk::Label.new
# seperated lines with \n
label.set_text("This is a left-justified label.\nWith multiple lines.")
# label justified by left
label.set_justify(Gtk::Justification::LEFT)
vbox_left.pack_start(label, :expand => true, :fill => true, :padding => 0)

label = Gtk::Label.new("This is a right-justified label.\nWith multiple lines.")
label.set_justify(Gtk::Justification::RIGHT)
vbox_left.pack_start(label, :expand => true, :fill => true, :padding => 0)

label = Gtk::Label.new(multi_line)
label.wrap = true
label.set_justify(Gtk::Justification::FILL)
vbox_right.pack_start(label, :expand => true, :fill => true, :padding => 0)

label = Gtk::Label.new
# use markup language in label text
label.set_markup("Text can be <small>small</small>, <big>big</big>, 
                  <b>bold</b>, <i>italic</i> and even point to
                  somewhere in the <a href=\"http://www.gtk.org\">Visit Gtk offical page</a>")
label.wrap = true
vbox_left.pack_start(label, :expand => true, :fill => true, :padding => 0)

label = Gtk::Label.new("_Press Alt + P to select button to the right", true)
vbox_left.pack_start(label, :expand => true, :fill => true,:padding => 0)
# enable label selection by true
label.set_selectable(true)
button = Gtk::Button.new(:label => "Click at your own risk")
label.set_mnemonic_widget(button)
vbox_right.pack_start(button, :expand => true, :fill => true, :padding => 0)

win.add(hbox)
win.signal_connect("destroy"){Gtk.main_quit}
win.show_all
Gtk.main

Mnemonics can be used in labels, the strings start with underscored character, it is used for keyboard navigation. Label initalizing function can get two arguments, first for text and second enables mnemonic: Gtk::Label.new("_Press Alt + P to select button to the right", true) . You also can initialize label without any argument then after set label with set_text(). Mnemonic is false as default.

We have used %{...} ruby special multi line string definition above. You can set markup using set_markup().

To justify label, you should use set_justify().