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MFC Topics: The Print Dialog Box

 

Introduction

Printing is usually considered as the ability to draw, on a piece of paper, the contents of a document. The document can be a picture (graphic), simple text, or rich text, etc. To make this possible, a printing device is primarily connected, wired or wirelessly, to a computer. This means that a type of connection must exist between both machines. The machine that holds the document is a computer equipped with a processor and it is loaded with the application that would open the document. The computer is responsible for various early assignments such as drawing the document on the computer screen for the user to preview. This allows the user to have an idea of what the printed result would look like, before sending it to the peripheral responsible for drawing it on paper.

To assist the users with printing, the Microsoft Windows operating system provides a convenient dialog box named Print. Based on this, to print from an application, a user usually clicks File -> PrintÖ from the main menu. In most applications, this action would display the Microsoft Windows Print dialog box.

The Print dialog is implemented in the MFC library through the CPrintDialog class. To programmatically display the Print dialog box, you can declare a variable of type CPrintDialog. The syntax of its constructor is:

CPrintDialog(BOOL bPrintSetupOnly,
	     DWORD dwFlags = PD_ALLPAGES | 
			     PD_USEDEVMODECOPIES | 
			     PD_NOPAGENUMS | 
			     PD_HIDEPRINTTOFILE | 
			     PD_NOSELECTION,
	     CWnd* pParentWnd = NULL );

Only one argument of this constructor is required and it is of type BOOL. To get the Print dialog box, pass this argument with a FALSE value.

Displaying the Print Dialog Box

When the user clicks File -> PrintÖ or decides to initiate printing, you should display the Print dialog box. To do this, after declaring a CPrintDialog variable with a FALSE value, you can call its DoModal() method whose syntax is:

virtual INT_PTR DoModal();

This would display the Print dialog box as it is defined in the Microsoft Windows operating systems:

The way this dialog box appears may depend on the operating system or the application. For example, here is the Print dialog box from Microsoft Office Word 2003:

Although many commercial applications provide a customized version of this dialog box, the functionality is primarily the same.

For the userís standpoint, the Print dialog box provides the various options used to customize the result that would display on a sheet of paper.

For a programmer with the MFC library, the information displayed on a Print dialog box is stored in an object based on a structure named CPrintInfo. As mentioned already, to start printing, the user would call the Print dialog box. When this is done, the application internally creates a CPrintInfo object. This object is made ready and available to you just before the user can see the Print dialog box. This gives you the time to change or customize what the user would see on the dialog box.

At the operating system level, the information of a Print dialog box is stored in a structure named PRINTDLG. To provide access to this structure in MFC, a CPrintDialog object is equipped with a member variable named m_pd. This member is simply a reference to a PRINTDLG object.

The Default Values of a Print Dialog Box

To make printing a little faster, when the Print dialog box comes up, it displays default characteristics that the user can accept and simply click OK to print, as we did in the previous sections. Those default characteristics are stored in (as members of) a PRINTDLG object. To get the default characteristics of the Print dialog that is displaying to the user, you can call the CPrintDialog::GetDefaults(). Its syntax is:

BOOL GetDefaults();

After calling this method, to get a particular value of the dialog box, you can access its corresponding member of the m_pd variable. We will review the members of the PRINTDLG structure in the new sections.

The Functionality of the Print Dialog Box

The Print dialog box displays the word Print as its caption. The right side is equipped with the help and the close buttons. The help button allows you to get information about a section or control on the dialog box. To use it, you can click it and click an object on the window.

Probably the most important section of the dialog box is a group labeled Select Printer or simply, Printer. This section is equipped with either a list view or a combo box named Name. This control displays the list of printers available to the user: it is the list of printers installed or mapped to the current computer. In order to print, this box should show at least one item. If there is no printer installed or mapped, when trying to print, the user may receive a warning or an error.

Before printing, the user must select a printer in the Name control. Because a print must have been installed for the user to select one, you cannot just add a name to this control. On the other hand, after a user has selected one, to get the name of the printer that the user selected, you can call the CPrintDialog::GetDeviceName() method. Its syntax is:

CString GetDeviceName() const;

As you can see, this method returns a string that represents the name of the selected printer.

Some applications, such as Adobe Acrobat, allow a user to start the process of printing but not actually print. The application would instead save the document to a file. Whether the user has such an application or not, the Print dialog box provides an alternative. It is equipped with a Print To File check box. The presence, behavior, or absence of the Print To File check box is controlled by three flags. To display the check box, you should add the PD_PRINTTOFILE value. Here is an example:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_PRINTTOFILE);
	dlg.DoModal();
}

If the user uses this check box and prints, he or she would be prompted to specify a name of a file in the Print To File dialog box:

After the user has entered a name and clicks OK, a file would be created and saved in the My Documents folder: this is the standard in Microsoft Windows. Some applications, such as Internet Explorer, allow you to specify the options:

In this case, you can specify a directory, using the Folders control, where to save the file and the file would receive a .prn extension. If you donít want the user to have the option of creating such a file, add the PD_DISABLEPRINTTOFILE flag to the dwFlags argument of the CPrintDialog constructor:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_ALLPAGES | PD_SELECTION | 
				PD_DISABLEPRINTTOFILE);
	
	dlg.DoModal();
}

This would only disable the control but to show the user that the operation cannot be carried at this time. As an alternative, if you donít even want the user to be aware of it, you can hide it. To do this, add the PD_HIDEPRINTTOFILE flag to the dwFlags argument:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_HIDEPRINTTOFILE);

	dlg.DoModal();
}

One of the options the user has (or may have) when printing is to decide whether to print the whole or part of the document. This is controlled in the Page Range section that displays three radio buttons. By default, the user is supposed to print the whole document. For this reason, the All radio button can be selected. This is the default-selected button of the Print Range section. In fact, if you create a CPrintDialog object with only the FALSE value as argument, only the All radio button would be allowed and it would be selected:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE);

	dlg.DoModal();
}

The option to have the All radio button is done with the PD_ALLPAGES flag of the dwFlags argument of the CPrintDialog() constructor. Suppose the document to print is made of text. Instead of printing everything, the user may want to first select a section of the document. Here is an example:

In this case, you can give the user the option to print the whole document or only the selected section. To print only the selection, the user can click the Selection radio button. To make this possible, you can simply add the PD_ALLPAGES flag when creating a CPrintDialog object. Here is an example:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_ALLPAGES);

	dlg.DoModal();
}

In this case, to print a selected section of the document, the user can click the Selection radio button. If you omit the PD_ALLPAGES flag, the Selection radio button is automatically disabled. As an alternative, if you want the Selection control to be selected by default when the Print dialog box comes up, add the PD_SELECTION flag to the dwFlags argument of the CPrintDialog object:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_ALLPAGES | PD_SELECTION);
	dlg.DoModal();
}

Imagine the document is made of various pages, such 12, after or without primarily selecting a section of the document, the user may want to print only one, two, or a range of pages, such as pages 4 to 6. To make this possible, the Print dialog box is equipped with the Pages radio button. By default, this option is not available. This is because the PD_NOPAGENUMS flag is set. You can reinforce this by adding the PD_NOPAGENUMS flag to the dwFlags argument of the CPrintDialog constructor. Here is an example:

void CExerciseDlg::OnBnClickedPrintBtn()
{
	// TODO: Add your control notification handler code here
	CPrintDialog dlg(FALSE, PD_ALLPAGES | PD_SELECTION |
				PD_NOPAGENUMS);
	dlg.DoModal();
}

If you want the user to be able to print a range of pages, the first action you must take is to enable this button. To do this, first add a PD_PAGENUMS flag to the dwFlags of the CPrintDialog constructor. There are other details to actually allow the user to print a range of pages.

By default, when the user decides to print, the dialog assumes that only one sample would be needed. In some cases, the user may want to print more than one sheet of paper. To specify the number of samples, the user can change the value of the Number Of Copies spin button.

If the user changes the value of the Number Of Copies control higher than one, the Collate check box becomes enabled. It allows the user to specify the sequence of printing the group of pages for each job.

After accepting the defaults or specifying the options on the Print dialog box, the user can click OK to send the job to the device.

 

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