Mega Code Archive
How to get notified when the content of the clipboard changes
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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.
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