You can find in the mORMotUILogin unit two methods matching this callback signature:

  TLoginForm = class(TForm)
    class procedure OnIdleProcess(Sender: TSQLRestClientURI; ElapsedMS: Integer);
    class procedure OnIdleProcessForm(Sender: TSQLRestClientURI; ElapsedMS: Integer);

The first OnIdleProcess() callback will change the mouse cursor shape to crHourClass after a defined period of time.
The OnIdleProcessForm() callback will display a pop-up window with a 'Please wait...' message, if the request takes even more time. Both will call Application.ProcessMessages to ensure the application User Interface is still responsive.

Some global variable were also defined to tune the behavior of those two callbacks:

  /// define when TLoginForm.OnIdleProcess() has to display the crHourGlass cursor
  // after a given time elapsed, in milliseconds
  // - default is 100 ms
  OnIdleProcessCursorChangeTimeout: integer = 100;

/// define when TLoginForm.OnIdleProcessForm() has to display the temporary // form after a given time elapsed, in milliseconds // - default is 2000 ms, i.e. 2 seconds OnIdleProcessTemporaryFormTimeout: integer = 2000;
/// define the message text displayed by TLoginForm.OnIdleProcessForm() // - default is sOnIdleProcessFormMessage resourcestring, i.e. 'Please wait...' OnIdleProcessTemporaryFormMessage: string;

You can therefore change those settings to customize the user experience. We tested it with a 3 second artificial temporizer for each request, and the applications were running smoothly, even if slowly - but comparable to most web applications, in fact. The SynFile main demo (available in the SQlite3MainDemo folder defines such a callback.

Note that this OnIdle feature is defined at TSQLRestClientURI class level, so is available for all communication protocols, not only HTTP but named pipes or in-process, so could be used to enhance user experience in case of some time consuming process.

Feedback is welcome on our forum, as usual.