mainfrm.pas

《Delphi开发人员指南》配书原码

unit MainFrm;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TMainForm = class(TForm)
    cbPrinters: TComboBox;
    lblPrinter: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure cbPrintersChange(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  MainForm: TMainForm;

implementation
uses IniFiles, Printers;

{$R *.DFM}

procedure TMainForm.FormCreate(Sender: TObject);
begin
  { Copy the printer names to the combobox and set the combobox to
    show the currently selected default printer }
  cbPrinters.Items.Assign(Printer.Printers);
  cbPrinters.Text := Printer.Printers[Printer.PrinterIndex];
  // Update the label to reflect the default printer 
  lblPrinter.Caption := Printer.Printers[Printer.PrinterIndex];
end;

procedure TMainForm.cbPrintersChange(Sender: TObject);
var
  IniFile: TIniFile;
  TempStr1, TempStr2: String;
  S: array[0..64] of char;
begin
  with Printer do
  begin
    // Set the new printer based on the ComboBox's selected printer
    PrinterIndex := cbPrinters.ItemIndex;
    // Store the printer name into a temporary string
    TempStr1 := Printers[PrinterIndex];
    // Delete the unnecessary portion of the printer name
    System.Delete(TempStr1, Pos(' on ', TempStr1), Length(TempStr1));
    // Create a TIniFile class
    IniFile := TIniFile.Create('WIN.INI');
    try
      // Retrieve the device name of the selected printer
      TempStr2 := IniFile.ReadString('Devices', TempStr1, '');
      // Change the default printer to that chosen by the user
      IniFile.WriteString('windows', 'device', TempStr1 + ',' + TempStr2);
      // Tell all windows that the default printer changed. 
      StrCopy(S, 'windows');
      SendMessage(HWND_BROADCAST, WM_WININICHANGE, 0, LongInt(@S));
    finally
      IniFile.Free;
    end;
  end;
  // Update the label to reflect the new printer selection 
  lblPrinter.Caption := Printer.Printers[Printer.PrinterIndex];
end;

end.