Printing a Document

Earlier we saw that many Windows components work together to generate your printed output. Within your .NET code, you will also use many components (classes) to drive the printing process. There are four main steps involved (at least directly) in printing a document from your code.

1.	Create an instance of a PrintDocument class (or add it as a control to your form).
2.	Set the PrintDocument's various printer settings, either by using a PrintDialog (or related) class/control, or by using the default or manual settings.
3.	Add an event handler for the PrintDocument's PrintPage event. This event is called once for each page, and receives a System.Drawing.Graphics object for the printer canvas. Your event handler code prints a single page, and updates a flag telling the document whether there are more pages to come.
4.	Call the PrintDocument's Print method to start the ball rolling.

Let's try a little code to see how this printing beast eats. Or prints. Or whatever it does. How about a simple program that prints a five-page document on the user's selected printer? The output will be a large single-digit page number, perfect for the Sesame Street set. First, let's create a new Windows Forms application, and add a single button to Form1 named ActPrint. We'll also add a PrintDocument control (named CountingDoc), and a PrintDialog control (named UserPrinter). Figure 19-5 shows the form and its supporting controls.

Figure 19-5. A program with only printing on its mind

These controls implement the first two of our four-step printing process. Next, we'll add the source code.

Public Class Form1    Private WhichPage As Integer    Private Sub ActPrint_Click(ByVal sender As System.Object, _          ByVal e As System.EventArgs) Handles ActPrint.Click       ' ----- Prompt the user for printer settings, and       ' start printing.       UserPrinter.Document = CountingDoc       If (UserPrinter.ShowDialog() = _          Windows.Forms.DialogResult.OK) Then _          CountingDoc.Print()    End Sub    Private Sub CountingDoc_BeginPrint(ByVal sender As Object, _          ByVal e As System.Drawing.Printing.PrintEventArgs) _          Handles CountingDoc.BeginPrint       ' ----- Start the counting over.       WhichPage = 1    End Sub    Private Sub CountingDoc_PrintPage(ByVal sender As Object, _          ByVal e As System.Drawing.Printing. _          PrintPageEventArgs) Handles CountingDoc.PrintPage       ' ----- Print a single page.       Dim hugeFont As Font       Dim centeredText As StringFormat       ' ----- Let's go overboard on the font: 256 points!       hugeFont = New Font("Arial", 256)       ' ----- Center the text on the page.       centeredText = New StringFormat()       centeredText.Alignment = StringAlignment.Center       centeredText.LineAlignment = StringAlignment.Center       ' ----- Print the number.       e.Graphics.DrawString(CStr(WhichPage), hugeFont, _          Brushes.Black, e.MarginBounds, centeredText)       ' ----- Draw the page margins to make it clear where       '       they are.       e.Graphics.DrawRectangle(Pens.Blue, e.MarginBounds)       ' ----- Limit the output to five pages.       WhichPage += 1       If (WhichPage <= 5) Then e.HasMorePages = True _          Else e.HasMorePages = False    End Sub End Class 

This code implements steps three (ActPrint_Click) and four (CountingDoc_PrintPage). The ActPrint button's Click event handler links the document and the Print Dialog so that they both refer to the same settings. It then prompts the user to select a printer and various options through the ShowDialog call. If the user clicks the OK button on that dialog, it triggers a call to the document's Print method.

The action then moves to the events of the PrintDocument instance. I've implemented two of the events: a BeginPrint event handler that performs some initialization, and a PrintPage event handler that does the hard work. (Other events include EndPrint, used to clean up when printing is complete, and QueryPageSettings, where you change the orientation and settings of each page of the document.) Actually, it's not all that hard, especially since we saw similar code in the chapter on GDI+. The biggest difference is the amount of space available on a printed page, allowing us to play with fonts in the hundreds of point sizes.

Figure 19-6 shows page two of the output from this program. I printed to the pseudo-printer installed with Microsoft's Windows Journal application. You can see in the bottom-right corner that it did properly record five output pages.

Figure 19-6. This page is brought to you by the number 2