Question

In this part of the Ruby GTK programming tutorial, we will introduce dialogs.

Dialog windows or dialogs are an indispensable part of most modern GUI applications. A dialog is defined as a conversation between two or more persons. In a computer application a dialog is a window which is used to "talk" to the application. A dialog is used to input data, modify data, change the application settings etc. Dialogs are important means of communication between a user and a computer program.

Message boxes

Message dialogs are convenient dialogs that provide messages to the user of the application. The message consists of textual and image data.

#!/usr/bin/ruby

'''
ZetCode Ruby GTK tutorial

This example shows message dialogs.

Author: Jan Bodnar
Website: www.zetcode.com
Last modified: May 2014
'''

require 'gtk3'


class RubyApp < Gtk::Window

  def initialize
    super
    
    init_ui
  end
  
  def init_ui
  
    table = Gtk::Table.new 2, 2, true
    
    info = Gtk::Button.new :label => "Information"
    warn = Gtk::Button.new :label => "Warning"
    ques = Gtk::Button.new :label => "Question"
    erro = Gtk::Button.new :label => "Error"

    info.signal_connect "clicked" do
      on_info
    end  
    
    warn.signal_connect "clicked" do
      on_warn
    end
    
    ques.signal_connect "clicked" do
      on_ques
    end
    
    erro.signal_connect "clicked" do
      on_erro
    end
    
    table.attach info, 0, 1, 0, 1
    table.attach warn, 1, 2, 0, 1
    table.attach ques, 0, 1, 1, 2
    table.attach erro, 1, 2, 1, 2
    
    add table
  
    set_title "Messages"
    signal_connect "destroy" do 
      Gtk.main_quit 
    end

    set_default_size 300, 100
    set_window_position :center
    
    show_all    

  end
  
  def on_info
 
    md = Gtk::MessageDialog.new :parent => self, 
      :flags => :destroy_with_parent, :type => :info, 
      :buttons_type => :close, :message => "Download completed"
    md.run
    md.destroy
  end
    
    
  def on_erro

    md = Gtk::MessageDialog.new :parent => self, 
      :flags => :modal, :type => :error, 
      :buttons_type => :close, :message => "Error loading file"
    md.run
    md.destroy
  end
  
  
  def on_ques

    md = Gtk::MessageDialog.new :parent => self, 
      :flags => :destroy_with_parent, :type => :question, 
      :buttons_type => :close, :message => "Are you sure to quit?"
    md.run
    md.destroy
  end
  
  def on_warn

    md = Gtk::MessageDialog.new :parent => self, 
      :flags => :destroy_with_parent, :type =>  :warning, 
      :buttons_type => :close, :message => "Unallowed operation"
    md.run
    md.destroy
  end
end

Gtk.init
  window = RubyApp.new
Gtk.main

In our example, we will show four kinds of message dialogs: information, warning, question and error message dialogs.

info = Gtk::Button.new :label => "Information"
warn = Gtk::Button.new :label => "Warning"
ques = Gtk::Button.new :label => "Question"
erro = Gtk::Button.new :label => "Error"

We have four buttons. Each of these buttons will show a different kind of message dialog.

def on_info

  md = Gtk::MessageDialog.new :parent => self, 
    :flags => :destroy_with_parent, :type => :info, 
    :buttons_type => :close, :message => "Download completed"
  md.run
  md.destroy
end

If we click on the info button, the information dialog is displayed. The Gtk::MessageDialog::INFO specifies the type of the dialog. The Gtk::MessageDialog::BUTTONS_CLOSE specifies the type of a button to be displayed in the dialog. The last parameter is the message displayed. The dialog is displayed with the run method. The programmer must also call either the destroy or the hide method.

AboutDialog

The AboutDialog displays information about the application. It can display a logo, the name of the application, version, copyright, website, or license information. It is also possible to give credits to the authors, documenters, translators, and artists.

#!/usr/bin/ruby

'''
ZetCode Ruby GTK tutorial

This example demonstrates the
Gtk::AboutDialog dialog.

Author: Jan Bodnar
Website: www.zetcode.com
Last modified: May 2014
'''

require 'gtk3'


class RubyApp < Gtk::Window

  def initialize
    super
  
    set_title "About dialog"
    signal_connect "destroy" do 
      Gtk.main_quit 
    end
    
    init_ui

    set_default_size 300, 150
    set_window_position :center
    
    show_all
  end
  
  def init_ui

    button = Gtk::Button.new :label => "About"
    button.set_size_request 80, 30
    
    button.signal_connect "clicked" do
      on_clicked
    end
    
    fix = Gtk::Fixed.new
    fix.put button, 20, 20
   
    add fix
  end
  
  def on_clicked
  
    about = Gtk::AboutDialog.new
    about.set_program_name "Battery"
    about.set_version "0.1"
    about.set_copyright "(c) Jan Bodnar"
    about.set_comments "Battery is a simple tool for battery checking"
    about.set_website "http://www.zetcode.com"    
        
    begin     
      logo = Gdk::Pixbuf.new :file => "batter.png"
      about.set_logo logo
    rescue IOError => e
      puts e
      puts "cannot load image"
      exit      
    end
    
    about.run
    about.destroy
  end
end

Gtk.init
  window = RubyApp.new
Gtk.main

The code example uses a Gtk::AboutDialog with some of its features.

about = Gtk::AboutDialog.new

We create the Gkt::AboutDialog widget.

about.set_program_name "Battery"
about.set_version "0.1"
about.set_copyright "(c) Jan Bodnar"

Here we specify the name, the version, and the copyright.

begin     
  logo = Gdk::Pixbuf.new :file => "batter.png"
  about.set_logo logo
rescue IOError => e
  puts e
  puts "cannot load image"
  exit      
end

This line creates a logo for the dialog. Some error checking is performed.

Figure: Gtk::AboutDialog

Gtk::FontSelectionDialog

The Gtk::FontSelectionDialog is a dialog for selecting fonts. It is typically used in applications that do some text editing or formatting.

#!/usr/bin/ruby

'''
ZetCode Ruby GTK tutorial

This example presents the Gtk::FontSelectionDialog.

Author: Jan Bodnar
Website: www.zetcode.com
Last modified: May 2014
'''

require 'gtk3'


class RubyApp < Gtk::Window

  def initialize
    super
    
    init_ui
  end
  
  def init_ui
  
    set_border_width 10
    @label = Gtk::Label.new "The only victory over love is flight."
    button = Gtk::Button.new :label => "Select font"
    
    button.signal_connect "clicked" do
      on_clicked
    end

    fix = Gtk::Fixed.new
    fix.put button, 100, 30
    fix.put @label, 30, 90
    add fix
    
    set_title "Gtk::FontSelectionDialog"
    signal_connect "destroy" do 
      Gtk.main_quit 
    end    
    
    set_default_size 300, 150
    set_window_position :center
    
    show_all    
  end
  
  def on_clicked

    fdia = Gtk::FontChooserDialog.new :title => "Select font name", 
      :parent => nil
    response = fdia.run
            
    if response == Gtk::ResponseType::OK
 
      font_desc = Pango::FontDescription.new fdia.font_desc
      if font_desc

        @label.override_font font_desc
      end
    end
    
    fdia.destroy
  end   
end

Gtk.init
  window = RubyApp.new
Gtk.main

In the code example, we have a button and a label. We show the Gtk::FontSelectionDialog by clicking on the button.

fdia = Gtk::FontSelectionDialog.new "Select font name"

We create the GtkFontSelectionDialog .

if response == Gtk::ResponseType::OK

  font_desc = Pango::FontDescription.new fdia.font_desc
  if font_desc

    @label.override_font font_desc
  end
end

If we click on the OK button, the font of the label widget changes to the one that we selected in the dialog.

Gtk::ColorSelectionDialog

The Gtk::ColorSelectionDialog is a dialog for selecting a colour.

#!/usr/bin/ruby

'''
ZetCode Ruby GTK tutorial

This example presents the Gtk::ColorSelectionDialog.

Author: Jan Bodnar
Website: www.zetcode.com
Last modified: May 2014
'''

require 'gtk3'


class RubyApp < Gtk::Window

  def initialize
    super
  
    init_ui
  end
  
  def init_ui
  
    set_border_width 10
    @label = Gtk::Label.new "The only victory over love is flight."
    button = Gtk::Button.new :label => "Select colour"
    
    button.signal_connect "clicked" do
      on_clicked
    end

    fix = Gtk::Fixed.new
    fix.put button, 100, 30
    fix.put @label, 30, 90
    add fix
    
    set_title "Gtk::ColorSelectionDialog"
    signal_connect "destroy" do 
      Gtk.main_quit 
    end    

    set_default_size 350, 150
    set_window_position :center
    
    show_all    
  end
  
  def on_clicked

    cdia = Gtk::ColorSelectionDialog.new :title => "Select colour"
    response = cdia.run
        
    if response == Gtk::ResponseType::OK
    
      colorsel = cdia.color_selection
      col = colorsel.current_rgba
      @label.override_color :normal, col
    end
    
    cdia.destroy
  end
end

Gtk.init
  window = RubyApp.new
Gtk.main

The example is very similar to the previous one. This time we change the colour of the label.

cdia = Gtk::ColorSelectionDialog.new :title => "Select colour"

We create the Gtk::ColorSelectionDialog .

if response == Gtk::ResponseType::OK

  colorsel = cdia.color_selection
  col = colorsel.current_rgba
  @label.override_color :normal, col
end

If we press the OK button, we get the colour value and modify the label's colour.

Figure: Gtk::ColorSelectionDialog

In this part of the Ruby GTK tutorial, we presented dialogs.