I did it this way:
My web modules which are running in a thread need to send strings to a memo on the main form.
FReceiverFromWS is a THandle
On create:
procedure TWebModuleWebServices.WebModuleCreate(Sender: TObject);
begin
FReceiverFromWS := FindWindow(PChar('TFormWebServices'),PChar(cFormCaption + FormWebServices.Instance)); // Search by class name and caption of receiving form
// ==> you could to that without form caption, but I need to distinguish between running services
if FReceiverFromWS = 0 then
begin
Assert(False,'CopyData receiver NOT found!'); // Probably TFormWebServices not yet created
Exit;
end;
end;
To send messages:
procedure TWebModuleWebServices.SendAMessage(Msg: String);
// Windows will guarantee that the data sent in the COPYDATASTRUCT will exist until after the WM_COPYDATA message
// has been carried out. As such, we must use SendMessage() to send a WM_COPYDATA message. We cannot use PostMessage().
var
lCopyDataStruct: TCopyDataStruct;
begin
lCopyDataStruct.dwData := 0;
lCopyDataStruct.cbData := 1 + Length(Msg);
lCopyDataStruct.lpData := PChar(Msg);
SendMessage(FReceiverFromWS, WM_COPYDATA, wParam(FReceiverFromWS), lParam(@lCopyDataStruct));
end;
In the main form, public method
procedure WMCopyData(var Msg : TWMCopyData) ; message WM_COPYDATA;
is:
procedure TFormWebServices.WMCopyData(var Msg: TWMCopyData);
var
i : integer;
s : string;
begin
i := Msg.CopyDataStruct.dwData;
case i of
0: begin // Message to display
s := String(PChar(Msg.CopyDataStruct.lpData));
AddMemoLine(s);
end;
1: begin // Statistical data
s := String(PChar(Msg.CopyDataStruct.lpData));
FrmWebServiceStats.CollectStats(s);
end;
end;
end;
(As you can see, I actually use dwData to signal the kind of message and handle these differently)