Title: Broadcast message within your application
Question: An elegant way to inform all controls within an application. Direct
references to all the TEdits or TCombos can be avoided !
Answer:
The Delphi class TWinControl has a handy function 'broadcast' to inform all controls within a form. An object needs an event-handler to react on these messages.
The message queue can be interrupted if Message.Result returns a value 0.
var i: integer;
hMessage: TMessage;
begin
hMessage.Msg := WM_USER + 1;
hMessage.WParam := 0;
hMessage.LParam := 0;
for i := 0 to Screen.FormCount-1 do
Screen.Forms[i].Broadcast(hMessage);
end;
With the help of TScreens its possible to send the message to all forms of the application.
This is a event-handler:
TMyButton = class(TButton)
protected
procedure EventHandler(var Message: TMessage);
message WM_USER + 1;
end;
...
procedure TMyButton.EventHandler(var Message: TMessage);
begin
// commands
Message.Result := 0; // Event continues
end;
Note that this communication is not asynchron !