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lock and unlock clipboard

Posted on 2001-09-15
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Last Modified: 2007-12-19
how can i lock and unlock the clipboard in code?

thanx

marc
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Question by:marksmall
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3 Comments
 
LVL 9

Accepted Solution

by:
ginsonic earned 200 total points
ID: 6495701
Read this tip . Hope to help you .

How to block pasting of text from the clipboard into an enabled TEdit
-----------------------------------------------------------

I have a TEdit on a form. How do I prevent someone from pasting text from the clipboard into it? The control has to be enabled, so please don't tell me to disable it.

Try this component, which blocks Cut, Copy and Paste:

unit MyEdit;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, stdctrls, clipbrd;

type
  TPreventNotifyEvent = procedure (Sender: TObject; Text: String; var Accept: Boolean) of Object;

type
  TMyEdit = class(TEdit)
  private
    FPreventCut: Boolean;
    FPreventCopy: Boolean;
    FPreventPaste: Boolean;
    FPreventClear: Boolean;

    FOnCut: TPreventNotifyEvent;
    FOnCopy: TPreventNotifyEvent;
    FOnPaste: TPreventNotifyEvent;
    FOnClear: TPreventNotifyEvent;

    procedure WMCut(var Message: TMessage); message WM_CUT;
    procedure WMCopy(var Message: TMessage); message WM_COPY;
    procedure WMPaste(var Message: TMessage); message WM_PASTE;
    procedure WMClear(var Message: TMessage); message WM_CLEAR;
  protected
    { Protected declarations }
  public
    { Public declarations }
  published
    property PreventCut: Boolean read FPreventCut write FPreventCut default False;
    property PreventCopy: Boolean read FPreventCopy write FPreventCopy default False;
    property PreventPaste: Boolean read FPreventPaste write FPreventPaste default False;
    property PreventClear: Boolean read FPreventClear write FPreventClear default False;
    property OnCut: TPreventNotifyEvent read FOnCut write FOnCut;
    property OnCopy: TPreventNotifyEvent read FOnCopy write FOnCopy;
    property OnPaste: TPreventNotifyEvent read FOnPaste write FOnPaste;
    property OnClear: TPreventNotifyEvent read FOnClear write FOnClear;
  end;

procedure Register;

implementation

procedure TMyEdit.WMCut(var Message: TMessage);
var
  Accept: Boolean;
  Handle: THandle;
  HandlePtr: Pointer;
  CText: String;
begin
  if FPreventCut then
    Exit;
  if SelLength = 0 then
    Exit;
  CText := Copy(Text, SelStart + 1, SelLength);
  try
    OpenClipBoard(Self.Handle);
    Accept := True;
    if Assigned(FOnCut) then
      FOnCut(Self, CText, Accept);
    if not Accept then
      Exit;
    Handle := GlobalAlloc(GMEM_MOVEABLE + GMEM_DDESHARE, Length( CText ) + 1);
    if Handle = 0 then
      Exit;
    HandlePtr := GlobalLock(Handle);
    Move((PChar(CText))^, HandlePtr^, Length(CText));
    SetClipboardData(CF_TEXT, Handle);
    GlobalUnlock(Handle);
    CText := Text;
    Delete(CText, SelStart + 1, SelLength);
    Text := CText;
  finally
    CloseClipBoard;
  end;
end;


procedure  TMyEdit.WMCopy(var Message: TMessage);
var
  Accept: Boolean;
  Handle: THandle;
  HandlePtr: Pointer;
  CText: String;
begin
  if FPreventCopy then
    Exit;
  if SelLength = 0 then
    Exit;
  CText := Copy(Text, SelStart + 1, SelLength);
  try
    OpenClipBoard(Self.Handle);
    Accept := True;
    if Assigned(FOnCopy) then
      FOnCopy(Self, CText, Accept);
    if not Accept then
      Exit;
    Handle := GlobalAlloc(GMEM_MOVEABLE + GMEM_DDESHARE, Length(CText) + 1);
    if Handle = 0 then
      Exit;
    HandlePtr := GlobalLock(Handle);
    Move((PChar(CText))^, HandlePtr^, Length(CText));
    SetClipboardData(CF_TEXT, Handle);
    GlobalUnlock(Handle);
  finally
    CloseClipBoard;
  end;
end;


procedure  TMyEdit.WMPaste(var Message: TMessage);
var
  Accept: Boolean;
  Handle: THandle;
  CText: String;
  LText: String;
  AText: String;
begin
  if FPreventPaste then
    Exit;
  if IsClipboardFormatAvailable(CF_TEXT) then
  begin
    try
      OpenClipBoard(Self.Handle);
      Handle := GetClipboardData(CF_TEXT);
      if Handle = 0 then
        Exit;
      CText := StrPas(GlobalLock(Handle));
      GlobalUnlock(Handle);
      Accept := True;
      if Assigned(FOnPaste) then
        FOnPaste(Self, CText, Accept);
      if not Accept then
        Exit;
      LText := '';
      if SelStart > 0 then
        LText := Copy( Text, 1, SelStart);
      LText := LText + CText;
      AText := '';
      if (SelStart + 1) < Length(Text) then
         AText := Copy(Text, SelStart + SelLength + 1, Length(Text) - SelStart + SelLength + 1));
      Text := LText + AText;
    finally
      CloseClipBoard;
    end;
  end;
end;


procedure TMyEdit.WMClear(var Message: TMessage);
var
  Accept: Boolean;
  CText: String;
begin
  if FPreventClear then
    Exit;
  if SelStart = 0 then
    Exit;
  CText := Copy(Text, SelStart + 1, SelLength);
  Accept := True;
  if Assigned(FOnClear) then
    FOnClear(Self, CText, Accept);
  if not Accept then
    Exit;
  CText := Text;
  Delete(CText, SelStart + 1, SelLength);
  Text := CText;
end;


procedure Register;
begin
  RegisterComponents('Samples', [TMyEdit]);
end;

end.
0
 
LVL 9

Expert Comment

by:ginsonic
ID: 6503322
Or ........

To copy something there has to be a selection, otherwise there is nothing to copy. So attach a handler to the controls OnSelectionChange event. This handler contains the line:

with Sender as TRichEdit do // put here your component
  SelLength := 0;


something like :

var
yourLock:Boolean;

if yourLock then
 with Sender as TEdit do
  SelLength := 0;
0
 

Author Comment

by:marksmall
ID: 6628352
SORRY ABOUT DELAY, BEEN POORLY AND COULD GET ACCESS TO MY COMPUTER!
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