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Disable paste in a TEdit?

Posted on 2006-07-14
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793 Views
Last Modified: 2012-05-05
Hi,

Is there an easy way to disable pasting (using a mouse)?

I need to fix a program where OnKeyUp is used for input validation. Ofcourse when data is pasted using the mouse, this event is not generated. But the problem is that I cannot simply change all events to an OnChange. So a quick fix would be simply not allowing pasting.

cwwkie
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Question by:cwwkie
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7 Comments
 
LVL 14

Author Comment

by:cwwkie
ID: 17108734
This is a simplified example of what is happening;

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    procedure Edit1KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
    procedure Edit2KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
    procedure FormShow(Sender: TObject);
    procedure EditChange(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  GlobalText1 : AnsiString;
  GlobalText2 : AnsiString;

implementation

{$R *.dfm}

procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  GlobalText1 := Edit1.Text;
  Edit2.Text := '';
end;

procedure TForm1.Edit2KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  GlobalText2 := Edit2.Text;
  Edit1.Text := '';
end;

procedure TForm1.FormShow(Sender: TObject);
begin
  GlobalText1 := 'test';
  GlobalText2 := '';

  Edit1.Text := GlobalText1;
  Edit2.Text := GlobalText2;
end;

procedure TForm1.EditChange(Sender: TObject);
begin
  SendMessage(TEdit(Sender).Handle, WM_KEYUP, 0, 0);
end;

end.

When I simply call the keyup eventhandler from the onchange, it will also be called when the data is manually changed (Edit2.Text := GlobalText2;), which will clear Edit1 on it's turn. So I need to change all the eventhandlers to avoid this, but because this takes time, I like to have an alternative in the mean time.
0
 
LVL 26

Accepted Solution

by:
Russell Libby earned 500 total points
ID: 17109024
You can subclass the edit and discard the message.

Regards,
Rusell

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

type
  TForm1            = class(TForm)
     Edit1:         TEdit;
     procedure      FormCreate(Sender: TObject);
  private
     // Private declarations
     FOldEditProc:  TWndMethod;
  protected
     // Protected declartions
     procedure      EditWndProc(var Message: TMessage);

  public
     // Public declarations
  end;

var
  Form1:            TForm1;

implementation
{$R *.DFM}

procedure TForm1.EditWndProc(var Message: TMessage);
begin

  if (Message.Msg = WM_PASTE) then
     Message.Result:=1
  else
     FOldEditProc(Message);

end;

procedure TForm1.FormCreate(Sender: TObject);
begin

  FOldEditProc:=Edit1.WindowProc;
  Edit1.WindowProc:=EditWndProc;

end;

end.
0
 
LVL 14

Author Comment

by:cwwkie
ID: 17109200
Yes, that will do it.
Thanks!
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LVL 6

Expert Comment

by:House_of_Dexter
ID: 17109292
in your 2nd problem you have a circular reference going on with your events...

Edit1.keyup calls edit1.change which calls keyup and so on and so on...

There's 2 ways to go about this...

one disable the event

procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
var
  aEventHolder: TNotifyEvent;
begin
  aEventHolder := Edit1.OnChange;
  try
    GlobalText1 := Edit1.Text;
    Edit2.Text := '';
  finally
    Edit1.OnChange := aEventHolder;
  end
end;


or better Create a State varible
I usually a Set

//TFormStateType ...use this if you need to know what the state is...
{CAREFUL...if you add to this...change TFormStateType}
const
  cEditKeyUp = 0;
  cEditChange = 1;
....add state that you are interested in here...
  cSomeStateChange =9;
 
 
cFormStateSet = [cEditKeyUp..cSomeStateChange ]

type
    TFormStateType =  cIsInitialize..cIsUpdateStatus;
    TFormStateSet = Set of TFormStateType;

//ususally declare something like this in Private of Form

  FFormState: TFormStateSet ;

procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  GlobalText1 := Edit1.Text;
  Edit2.Text := '';
  FFormState := FFormState + cEditKeyUp ;
end;

procedure TForm1.EditChange(Sender: TObject);
begin
  if cEditKeyUp in FFormState then
    FFormState :=  FFormState - cEditKeyUp
  else
    SendMessage(TEdit(Sender).Handle, WM_KEYUP, 0, 0);
end;

0
 
LVL 6

Expert Comment

by:House_of_Dexter
ID: 17109439
procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
var
  aEventHolder: TNotifyEvent;
begin
  aEventHolder := Edit1.OnChange;
  try
   Edit1.OnChange := nil;  <--forgot this
    GlobalText1 := Edit1.Text;
    Edit2.Text := '';
  finally
    Edit1.OnChange := aEventHolder;
  end
end;
0
 
LVL 14

Author Comment

by:cwwkie
ID: 17111804
> in your 2nd problem you have a circular reference going on with your events...

But If I disable pasting, I don't need the onchange, and have no circular reference. As soon as I have properly implemeted a good OnChange for all edit's, I can enable pasting (and cutting) again.
0
 
LVL 6

Expert Comment

by:House_of_Dexter
ID: 17114413
True...but if you ever implement an OnChange you will need to do something like I showed...
0

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