unit1.pas

在delphi中实现windows核心编程.原书光盘代码核心编程.原书光盘代码

unit Unit1;

interface

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

type
  TPasswordEdit = class(TEdit)
  private
    FFalsePassword: TCaption;
    FAllowPasswordRead: Boolean;
    FAllowPasswordCharChange: Boolean;
    function GetPasswordChar: Char;
    function GetText: TCaption;
    procedure SetPasswordChar(const Value: Char);
    procedure SetText(const Value: TCaption);
  public
    constructor Create(AOwner: TComponent); override;
    procedure DefaultHandler(var Message); override;
  published
    property AllowPasswordCharChange: Boolean read FAllowPasswordCharChange write FAllowPasswordCharChange;
    property AllowPasswordRead: Boolean read FAllowPasswordRead write FAllowPasswordRead;
    property PasswordChar: Char read GetPasswordChar write SetPasswordChar default '*';
    property FalsePassword: TCaption read FFalsePassword write FFalsePassword;
    property Text: TCaption read GetText write SetText;
  end;

  TForm1 = class(TForm)
    Edit1: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    PasswordEdit1: TPasswordEdit;
  end;
var
  Form1: TForm1;

implementation

{$R *.DFM}

constructor TPasswordEdit.Create(AOwner: TComponent);
begin
  AllowPasswordCharChange := true;
  AllowPasswordRead := true;
  inherited Create(AOwner);
  AllowPasswordCharChange := false;
  AllowPasswordRead := false;
  PasswordChar := '*'; {显示*}
end;

procedure TPasswordEdit.SetPasswordChar(const Value: Char);
var
  OldAPCC, OldAPR: boolean;
begin
  OldAPCC := FAllowPasswordCharChange;
  OldAPR := FAllowPasswordRead;
  FAllowPasswordCharChange := true;
  FAllowPasswordRead := true;
  if HandleAllocated then
    inherited PasswordChar := Char(Sendmessage(Handle, EM_GETPASSWORDCHAR, 0, 0));
  inherited PasswordChar := Value;
  FAllowPasswordCharChange := OldAPCC;
  FAllowPasswordRead := OldAPR;
end;

function TPasswordEdit.GetPasswordChar: Char;
begin
  if HandleAllocated then
    Result := Char(Sendmessage(Handle, EM_GETPASSWORDCHAR, 0, 0))
  else
    Result := inherited PasswordChar;
end;

procedure TPasswordEdit.SetText(const Value: TCaption);
begin
  inherited Text := Value;
end;

function TPasswordEdit.GetText: TCaption;
var
  OldAPCC, OldAPR: boolean;
begin
  OldAPCC := FAllowPasswordCharChange;
  OldAPR := FAllowPasswordRead;
  FAllowPasswordCharChange := true;
  FAllowPasswordRead := true;
  Result := inherited Text;
  FAllowPasswordCharChange := OldAPCC;
  FAllowPasswordRead := OldAPR;
end;

procedure TPasswordEdit.DefaultHandler(var Message);
var
  P: PChar;
begin
  if (csDesigning in ComponentState) or (csCreating in ControlState) then
    inherited
  else
    with TMessage(Message) do
      case msg of
        EM_SETPASSWORDCHAR: if FAllowPasswordCharChange then
            inherited;
        WM_GETTEXT: if FAllowPasswordRead then inherited
          else begin
            P := PChar(FFalsePassword);
            Result := StrLen(StrLCopy(PChar(LParam), P, WParam - 1));
          end;
        WM_GETTEXTLENGTH: if FAllowPasswordRead then inherited
          else
            if PChar(FFalsePassword) = nil then Result := 0
            else Result := StrLen(PChar(FFalsePassword));
      else
        inherited;
      end
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  PasswordEdit1 := TPasswordEdit.Create(self);
  PasswordEdit1.parent := form1;
  PasswordEdit1.Width := 150;
  PassWordEdit1.Height := 21;
  PasswordEdit1.Top := 115;
  PasswordEdit1.Left := 80;
  PasswordEdit1.PasswordChar := '*';
  PasswordEdit1.AllowPasswordRead := false;
  PasswordEdit1.Visible := true;
  PasswordEdit1.Text:='Hello';
  PasswordEdit1.FalsePassword:= '想读我？没门！'
end;

end.