Introduction to Print Preview

Introduction

If you use the printing process that solely involves the print dialog box, you may send a document to the printer without knowing what the printed document would look like on the piece of paper. In the same way, the user would have to simply accept the way you designed the printed document to appear. One way you can assist the user consists of displaying a preview of what the printed sheet would look like. This is the idea behind the concept of print preview.

Print preview consists of displaying, on the computer monitor, a sample representation of what the document would look like once printed.

  

Providing Print Preview

Print preview is primarily a technique of drawing a sample printed sheet on a form. It is implemented by the PrintPreviewDialog button from the Toolbox. Therefore, at design time, to provide print preview, from the Printing section of the Toolbox and click the form. As its name indicates, the dialog box is already created but like the other dialog boxes of the .NET Framework, you must add it to a form in order to make it available in your application.

In the .NET Framework, print preview is implemented through the PrintPreviewDialog class. This class is derived from the Form class. Based on this, to programmatically create a print preview, you can start by declaring a variable of type PrintPreviewDialog. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Friend WithEvents PrintPreviewer As Button

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            PrintPreviewer = New Button
            PrintPreviewer.Location = New Point(12, 12)
            PrintPreviewer.Text = "&Print Preview..."
            PrintPreviewer.Width = 100

            Controls.Add(PrintPreviewer)
        End Sub

        Private Sub PrintPreviewerClicked(ByVal sender As Object, _
                                 ByVal e As EventArgs) _
                                 Handles PrintPreview.Click
            Dim Previewer As PrintPreviewDialog = New PrintPreviewDialog
        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

As a dialog-based object, to display the print preview, the PrintPreviewDialog class inherits the ShowDialog() method from its parent the Form class. Here is an example:

Private Sub PrintPreviewerClicked(ByVal sender As Object, _
                                 ByVal e As EventArgs) _
                                 Handles PrintPreview.Click
            Dim Previewer As PrintPreviewDialog = New PrintPreviewDialog
            Previewer.ShowDialog()
End Sub

This would produce:

The Print Preview window appears as a finished designed form with a toolbar, a preview area, and two scroll bars.

The preview area shows a sample of what a printed sheet would look like. If the dialog box is not "aware" of what would be printed, it displays the "Document does not contain any pages" string. This means that, in order to display something, you must create and design it. To make this possible, the PrintPreviewDialog class is equipped with a property named Document. The PrintPreviewDialog.Document property is of type PrintDocument. Therefore, in order to design a sample sheet, you should have created and configured a PrintDocument object. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms
Imports System.Drawing.Printing

Module Exercise

    Public Class Starter
        Inherits Form

        Friend WithEvents PrintPreview As Button
        Private Previewer As PrintPreviewDialog
        Private DocumentToPrint As PrintDocument

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            PrintPreview = New Button
            PrintPreview.Location = New Point(12, 12)
            PrintPreview.Text = "&Print Preview..."
            PrintPreview.Width = 100

            Controls.Add(PrintPreview)

            Previewer = New PrintPreviewDialog()
            DocumentToPrint = New PrintDocument()

            Previewer.Document = DocumentToPrint
        End Sub

        Private Sub PrintPreviewClicked(ByVal sender As Object, _
                                 ByVal e As EventArgs) _
                                 Handles PrintPreview.Click
            Previewer.ShowDialog()
        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

This would produce:

As you can see, simply assigning a PrintDocument object to a print preview form only creates a blank sheet. In order to show a preview, you must design it. To make this possible, the PrintDocument class

To assist you with actually designing what you want to display in the preview area, the PrintDocument class fires an event named PrintPage. This event is of type PrintPageEventArgs. The PrintPageEventArgs class is equipped with a property named Graphics, which is of type Graphics. You can then use your knowledge of the Graphics class to create or design the preview. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms
Imports System.Drawing.Printing

Module Exercise

    Public Class Starter
        Inherits Form

        Friend WithEvents PrintPreview As Button
        Private Previewer As PrintPreviewDialog
        Friend WithEvents DocumentToPrint As PrintDocument

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            PrintPreview = New Button
            PrintPreview.Location = New Point(12, 12)
            PrintPreview.Text = "&Print Preview..."
            PrintPreview.Width = 100

            Controls.Add(PrintPreview)

            Previewer = New PrintPreviewDialog()
            DocumentToPrint = New PrintDocument()

            Previewer.Document = DocumentToPrint
        End Sub

        Private Sub PrintPreviewClicked(ByVal sender As Object, _
                                 ByVal e As EventArgs) _
                                 Handles PrintPreview.Click
            Previewer.ShowDialog()
        End Sub

        Private Sub DrawDocument(ByVal sender As Object, _
                                 ByVal e As PrintPageEventArgs) _
                                 Handles DocumentToPrint.PrintPage
            Dim imgPerson As Image = Image.FromFile("E:\Programs\persons1.gif")
            e.Graphics.DrawImage(imgPerson, 10, 10)
        End Sub
    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

On our computer, this produced:

To print the contents of the preview area, the user can click the Print button from the toolbar. Two things would happen. The compiler would select the default printer and the document would be sent directly to that printer. This means that, first there should be a (known) default printer and the user should know what that printer is second, the user would not be able to change the printer if more than one is available. If you want the user to be able to select the printer, you should provide a Print dialog box that the user can probably access from a menu of the application.

By default, when the print preview window appears to the user, it assumes some default dimensions that may make it small. Because it is derived from the Form class, you can maximize it if you want. Here is an example:

Private Sub PrintPreviewClicked(ByVal sender As Object, _
                                 ByVal e As EventArgs) _
                                 Handles PrintPreview.Click
            Previewer.WindowState = FormWindowState.Maximized
            Previewer.ShowDialog()
End Sub

If the print preview is not maximized, the content of the preview area may appear (too) small for the user, especially if it is made of text. To enlarge it, the user has two alternatives. If the user maximizes the window, the preview area would also be enlarged and the content would be easier to see. As an alternative, the user can click the arrow of the Zoom button. This would display a list of the zoom rates:

The user can then click one of the values.

So far, we were assuming that the user was printing a one-page document. With some files, the document may span more than one page. By default, when the print preview comes up, the preview are would display only one page. The user has the choice of displaying two or more pages at a time, even to specify some arrangement of these pages. To support this, the toolbar of the print preview is equipped with various buttons labeled One Page, Two Pages, Three Pages, Four Pages, and Six Pages.

After using the print preview, the user can close it.