LPPRINTHOOKPROC callback function (commdlg.h)

Receives messages or notifications intended for the default dialog box procedure of the Print dialog box. This is an application-defined or library-defined callback function that is used with the PrintDlg function.

The LPPRINTHOOKPROC type defines a pointer to this callback function. PrintHookProc is a placeholder for the application-defined or library-defined function name.

Syntax

LPPRINTHOOKPROC Lpprinthookproc;

UINT_PTR Lpprinthookproc(
  HWND unnamedParam1,
  UINT unnamedParam2,
  WPARAM unnamedParam3,
  LPARAM unnamedParam4
)
{...}

Parameters

unnamedParam1

A handle to the Print dialog box for which the message is intended.

unnamedParam2

The identifier of the message being received.

unnamedParam3

Additional information about the message. The exact meaning depends on the value of the unnamedParam2 parameter.

unnamedParam4

Additional information about the message. The exact meaning depends on the value of the unnamedParam2 parameter.

If the unnamedParam2 parameter indicates the WM_INITDIALOG message, unnamedParam4 is a pointer to a PRINTDLG structure containing the values specified when the dialog box was created.

Return value

If the hook procedure returns zero, the default dialog box procedure processes the message.

If the hook procedure returns a nonzero value, the default dialog box procedure ignores the message.

Remarks

When you use the PrintDlg function to create a Print dialog box, you can provide a PrintHookProc hook procedure to process messages or notifications intended for the dialog box procedure. To enable the hook procedure, use the PRINTDLG structure that you passed to the dialog creation function. Specify the address of the hook procedure in the lpfnPrintHook member and specify the PD_ENABLEPRINTHOOK flag in the Flags member.

The default dialog box procedure processes the WM_INITDIALOG message before passing it to the hook procedure. For all other messages, the hook procedure receives the message first. Then, the return value of the hook procedure determines whether the default dialog procedure processes the message or ignores it.

If the hook procedure processes the WM_CTLCOLORDLG message, it must return a valid brush handle to painting the background of the dialog box. In general, if the hook procedure processes any WM_CTLCOLOR* message, it must return a valid brush handle to painting the background of the specified control.

Do not call the EndDialog function from the hook procedure. Instead, the hook procedure can call the PostMessage function to post a WM_COMMAND message with the IDABORT value to the dialog box procedure. Posting IDABORT closes the dialog box and causes the dialog box function to return FALSE. If you need to know why the hook procedure closed the dialog box, you must provide your own communication mechanism between the hook procedure and your application.

You can subclass the standard controls of a common dialog box. However, the dialog box procedure may also subclass the controls. Because of this, you should subclass controls when your hook procedure processes the WM_INITDIALOG message. This ensures that your subclass procedure receives the control-specific messages before the subclass procedure set by the dialog box procedure.

Requirements

   
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header commdlg.h (include Windows.h)

See also

Common Dialog Box Library

Conceptual

EndDialog

PRINTDLG

PostMessage

PrintDlg

Reference

WM_CTLCOLORDLG

WM_INITDIALOG