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copied!<p>Broadcast a custom message to all windows. Only your window will know how to react to it. It can then reply with its current HWND in another message so the broadcaster does not have to hunt for it manually. Use RegisterWindowMessage() to register unique message IDs that other apps will ignore. For example:</p> <p>App 1:</p> <pre><code>var WM_WHERE_ARE_YOU: UINT = 0; WM_HERE_I_AM: UINT = 0; App2Wnd: HWND = 0; procedure TApp1Form.FromCreate(Sender: TObject); begin // use whatever string names you want, as long as they match App 2... WM_WHERE_ARE_YOU := RegisterWindowMessage("WhereAreYou"); WM_HERE_I_AM := RegisterWindowMessage("HereIAm"); end; procedure TApp1Form.WndProc(var Message: TMessage); begin if (Message.Msg = WM_HERE_I_AM) and (WM_HERE_I_AM <> 0) then App2Wnd := HWND(Message.LParam) else inherited; end; procedure TApp1Form.SendData(const copyDataStruct: TCopyDataStruct); var res : integer; procedure FindApp2Window; var Ignore: DWORD; begin App2Wnd := 0; if WM_WHERE_ARE_YOU = 0 then Exit; SendMessageTimeout(HWND_BROADCAST, WM_WHERE_ARE_YOU, 0, Longint(Self.Handle), SMTO_NORMAL, 500, Ignore); if App2Wnd = 0 then Application.ProcessMessages; end; begin FindApp2Window; if App2Wnd = 0 then begin ShowMessage(Format('Unable to find MainForm'); Exit; end; res := SendMessage(App2Wnd, WM_COPYDATA, Longint(Self.Handle), Longint(@copyDataStruct)); ... end; </code></pre> <p>App 2:</p> <pre><code>var WM_WHERE_ARE_YOU: UINT = 0; WM_HERE_I_AM: UINT = 0; procedure TApp2Form.FromCreate(Sender: TObject); begin // use whatever string names you want, as long as they match App 1... WM_WHERE_ARE_YOU := RegisterWindowMessage("WhereAreYou"); WM_HERE_I_AM := RegisterWindowMessage("HereIAm"); end; procedure TApp2Form.WndProc(var Message: TMessage); begin case Message.Msg of WM_COPYDATA: begin if PCopyDataStruct(Message.LParam)^.dwData = ... then begin ... Message.Result := 1; Exit; end; end; ... else if (Message.Msg = WM_WHERE_ARE_YOU) and (WM_WHERE_ARE_YOU <> 0) then begin if WM_HERE_I_AM <> 0 then PostMessage(HWND(Message.LParam), WM_HERE_I_AM, 0, Longint(Self.Handle)); Exit; end; end; inherited; end; </code></pre>

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