How-to-get-notified-when-the-content-of-the-clipboard-changes


            Title: How to get notified when the content of the clipboard changes
unit Unit1;
interface
uses
 Windows, Messages, Forms, Classes, Controls, StdCtrls;
type
 TForm1 = class(TForm)
 Button1: TButton;
 Button2: TButton;
 procedure Button1Click(Sender : TObject);
 procedure Button2Click(Sender : TObject);
 procedure FormCreate(Sender : TObject);
 procedure FormDestroy(Sender : TObject);
 private
 FNextClipboardViewer: HWND;
 procedure WMChangeCBChain(var Msg : TWMChangeCBChain); message WM_CHANGECBCHAIN;
 procedure WMDrawClipboard(var Msg : TWMDrawClipboard); message WM_DRAWCLIPBOARD;
 end;
var
 Form1 : TForm1;
implementation
{$R *.DFM}
procedure TForm1.FormCreate(Sender : TObject);
begin
 { Initialize variable }
 FNextClipboardViewer := 0;
end;
procedure TForm1.Button1Click(Sender : TObject);
begin
 if FNextClipboardViewer 0 then
 MessageBox(0, 'This window is already registered!', nil, 0)
 else
 { Add to clipboard chain }
 FNextClipboardViewer := SetClipboardViewer(Handle);
end;
procedure TForm1.Button2Click(Sender : TObject);
begin
 { Remove from clipboard chain }
 ChangeClipboardChain(Handle, FNextClipboardViewer);
 FNextClipboardViewer := 0;
end;
procedure TForm1.WMChangeCBChain(var Msg : TWMChangeCBChain);
begin
 inherited;
 { mark message as done }
 Msg.Result := 0;
 { the chain has changed }
 if Msg.Remove = FNextClipboardViewer then
 { The next window in the clipboard viewer chain had been removed. We recreate it. }
 FNextClipboardViewer := Msg.Next
 else
 { Inform the next window in the clipboard viewer chain }
 SendMessage(FNextClipboardViewer, WM_CHANGECBCHAIN, Msg.Remove, Msg.Next);
end;
procedure TForm1.WMDrawClipboard(var Msg : TWMDrawClipboard);
begin
 inherited;
 { Clipboard content has changed }
 try
 MessageBox(0, 'Clipboard content has changed!', 'Clipboard Viewer', MB_ICONINFORMATION);
 finally
 { Inform the next window in the clipboard viewer chain }
 SendMessage(FNextClipboardViewer, WM_DRAWCLIPBOARD, 0, 0);
 end;
end;
procedure TForm1.FormDestroy(Sender : TObject);
begin
 if FNextClipboardViewer 0 then
 begin
 { Remove from clipboard chain }
 ChangeClipboardChain(Handle, FNextClipboardViewer);
 FNextClipboardViewer := 0;
 end;
end;
end.
System Delphi
