Question

In this part of the Visual Basic 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.

' ZetCode Mono Visual Basic GTK# tutorial
'
' This program shows message dialogs.
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports Gtk
 
Public Class GtkVBApp
  Inherits Window
 
  Public Sub New
    
    MyBase.New("Message dialogs")
    
    Me.InitUI
    
    Me.SetDefaultSize(250, 100)
    Me.SetPosition(WindowPosition.Center)
    AddHandler Me.DeleteEvent, AddressOf Me.OnDelete

    Me.ShowAll  
    
  End Sub
  
  Private Sub InitUI
  
    Dim table As New Table(2, 2, True)
    
    Dim info As New Button("Information")
    Dim warn As New Button("Warning")
    Dim ques As New Button("Question")
    Dim erro As New Button("Error")

    AddHandler info.Clicked, AddressOf Me.OnInfo
    AddHandler warn.Clicked, AddressOf Me.OnWarning
    AddHandler ques.Clicked, AddressOf Me.OnQuestion
    AddHandler erro.Clicked, AddressOf Me.OnError
  
    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)
    
    Me.Add(table)

  End Sub
  
  Private Sub OnInfo(ByVal sender As Object, ByVal args As EventArgs)
    Dim md As MessageDialog = New MessageDialog(Me, _
      DialogFlags.DestroyWithParent, MessageType.Info, _ 
      ButtonsType.Close, "Download completed")
    md.Run
    md.Destroy
  End Sub
  
  Private Sub OnWarning(ByVal sender As Object, ByVal args As EventArgs)
    Dim md As MessageDialog = New MessageDialog(Me, _
      DialogFlags.DestroyWithParent, MessageType.Warning, _
      ButtonsType.Close, "Unallowed operation")
    md.Run
    md.Destroy
  End Sub
  
  Private Sub OnQuestion(ByVal sender As Object, ByVal args As EventArgs)
    Dim md As MessageDialog = New MessageDialog(Me, _
      DialogFlags.DestroyWithParent, MessageType.Question, _
      ButtonsType.Close, "Are you sure to quit?")
    md.Run
    md.Destroy
  End Sub
  
  Private Sub OnError(ByVal sender As Object, ByVal args As EventArgs)
    Dim md As MessageDialog = New MessageDialog(Me, _
      DialogFlags.DestroyWithParent, MessageType.Error, _
      ButtonsType.Close, "Error loading file")
    md.Run
    md.Destroy
  End Sub
   
  Private Sub OnDelete(ByVal sender As Object, _
      ByVal args As DeleteEventArgs)
    Application.Quit
  End Sub

  Public Shared Sub Main
  
    Application.Init
    Dim app As New GtkVBApp
    Application.Run
    
  End Sub
 
End Class

In our example, we will show four kinds of message dialogs. Information, Warning, Question and Error message dialogs.

Dim info As New Button("Information")
Dim warn As New Button("Warning")
Dim ques As New Button("Question")
Dim erro As New Button("Error")

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

Private Sub OnInfo(ByVal sender As Object, ByVal args As EventArgs)
  Dim md As MessageDialog = New MessageDialog(Me, _
    DialogFlags.DestroyWithParent, MessageType.Info, _ 
    ButtonsType.Close, "Download completed")
  md.Run
  md.Destroy
End Sub

If we click on the info button, the Information dialog is displayed. The MessageType.Info specifies the type of the dialog. The ButtonsType.Close specifies the button to be displayed in the dialog. The last parameter is the message dislayed. 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. AboutDialog can display a logo, the name of the application, version, copyright, website or licence information. It is also possible to give credits to the authors, documenters, translators and artists.

' ZetCode Mono Visual Basic GTK# tutorial
'
' This program shows the about
' dialog
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports Gtk
 
Public Class GtkVBApp
  Inherits Window
 
  Public Sub New
    
    MyBase.New("About dialog")
    
    Me.InitUI
    
    Me.SetDefaultSize(350, 300)
    Me.SetPosition(WindowPosition.Center)
    AddHandler Me.DeleteEvent, AddressOf Me.OnDelete

    Me.ShowAll
    
  End Sub
  
  Private Sub InitUI
  
    Dim button As New Button("About")
    
    AddHandler button.Clicked, AddressOf Me.ShowDialog
    
    Dim fixed As New Fixed
    fixed.Put(button, 20, 20)
    Me.Add(fixed)

  End Sub
  
  Private Sub ShowDialog(ByVal sender As Object, _
      ByVal args As EventArgs)
  
    Dim about As New AboutDialog
    about.ProgramName = "Battery"
    about.Version = "0.1"
    about.Copyright = "(c) Jan Bodnar"
    about.Comments = "Battery is a simple tool for battery checking"
    about.Website = "http://www.zetcode.com"
    about.Logo = New Gdk.Pixbuf("battery.png")
    about.Run
    about.Destroy

  End Sub

   
  Sub OnDelete(ByVal sender As Object, _
      ByVal args As DeleteEventArgs)
    Application.Quit
  End Sub

  Public Shared Sub Main
  
    Application.Init
    Dim app As New GtkVBApp
    Application.Run
    
  End Sub
 
End Class

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

Dim about As New AboutDialog

We create an AboutDialog .

Dim about As New AboutDialog
about.ProgramName = "Battery"
about.Version = "0.1"
about.Copyright = "(c) Jan Bodnar"

By setting the properties of the dialog, we specify the name, version and the copyright.

about.Logo = New Gdk.Pixbuf("battery.png")

This line creates a logo.

Figure: AboutDialog

FontSelectionDialog

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

' ZetCode Mono Visual Basic GTK# tutorial
'
' This program shows the FontSelectionDialog
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com

Imports Gtk


Public Class GtkVBApp
  Inherits Window
 
  Dim label As Label 
 
  Public Sub New
    
    MyBase.New("Font dialog")
    
    Me.InitUI
    
    Me.SetDefaultSize(350, 300)
    Me.SetPosition(WindowPosition.Center)
    AddHandler Me.DeleteEvent, AddressOf Me.OnDelete

    Me.ShowAll  
    
  End Sub
  
  Private Sub InitUI 
  
    label = New Label("The only victory over love is flight.")
    Dim button As New Button("Select font")
    
    AddHandler button.Clicked, AddressOf Me.ShowDialog

    Dim fixed As New Fixed
    fixed.Put(button, 100, 30)
    fixed.Put(label, 30, 90)
    Me.Add(fixed)

  End Sub
  
  Private Sub ShowDialog(ByVal sender As Object, _
      ByVal args As EventArgs)
  
    Dim fdia As New FontSelectionDialog("Select font name")
    
    AddHandler fdia.Response, AddressOf Me.SelectFont
   
    fdia.Run
    fdia.Destroy

  End Sub
  
  Private Sub SelectFont(ByVal sender As Object, _
      ByVal args As ResponseArgs)
    
    If args.ResponseId = ResponseType.Ok
      Dim fontdesc As Pango.FontDescription = _
        Pango.FontDescription.FromString(sender.FontName)
      label.ModifyFont(fontdesc)
    End If
  
  End Sub
   
  Sub OnDelete(ByVal sender As Object, _
      ByVal args As DeleteEventArgs)
    Application.Quit
  End Sub

  Public Shared Sub Main
  
    Application.Init
    Dim app As New GtkVBApp
    Application.Run
    
  End Sub
 
End Class

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

Dim fdia As New FontSelectionDialog("Select font name")

We create the FontSelectionDialog .

If args.ResponseId = ResponseType.Ok
  Dim fontdesc As Pango.FontDescription = _
    Pango.FontDescription.FromString(sender.FontName)
  label.ModifyFont(fontdesc)
End If

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

Figure: FontSelectionDialog

ColorSelectionDialog

ColorSelectionDialog is a dialog for selecting a color.

' ZetCode Mono Visual Basic GTK# tutorial
'
' This program shows the ColorSelectionDialog
'
' author jan bodnar
' last modified May 2009
' website www.zetcode.com


Imports Gtk
 
Public Class GtkVBApp
  Inherits Window
 
  Dim label As Label 
 
  Public Sub New
    
    MyBase.New("Color dialog")
    
    Me.InitUI
    
    Me.SetDefaultSize(350, 300)
    Me.SetPosition(WindowPosition.Center)
    AddHandler Me.DeleteEvent, AddressOf Me.OnDelete

    Me.ShowAll  
    
  End Sub
  
  Private Sub InitUI
  
    label = New Label("The only victory over love is flight.")
    Dim button As New Button("Select color")
    
    AddHandler button.Clicked, AddressOf Me.ShowDialog

    Dim fixed As New Fixed
    fixed.Put(button, 100, 30)
    fixed.Put(label, 30, 90)
    Me.Add(fixed)

  End Sub
  
  Private Sub ShowDialog(ByVal sender As Object, _
      ByVal args As EventArgs)
  
    Dim cdia As New ColorSelectionDialog("Select color")
    
    AddHandler cdia.Response, AddressOf Me.SelectColor
   
    cdia.Run
    cdia.Destroy

  End Sub
  
  Private Sub SelectColor(ByVal sender As Object, _
      ByVal args As ResponseArgs)

    If args.ResponseId = ResponseType.Ok
      label.ModifyFg(StateType.Normal, _
        sender.ColorSelection.CurrentColor)
    End If
  
  End Sub

   
  Sub OnDelete(ByVal sender As Object, _
      ByVal args As DeleteEventArgs)
    Application.Quit
  End Sub

  Public Shared Sub Main
  
    Application.Init
    Dim app As New GtkVBApp
    Application.Run
    
  End Sub
 
End Class

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

Dim cdia As New ColorSelectionDialog("Select color")

We create the ColorSelectionDialog .

If args.ResponseId = ResponseType.Ok
  label.ModifyFg(StateType.Normal, _
    sender.ColorSelection.CurrentColor)
End If

If the user pressed OK, we get the color value and modify the label's color.

Figure: ColorSelectionDialog

In this part of the Visual Basic GTK# tutorial, we presented dialogs.