Re: Tweaking default java.awt.Robot settings

[David Herron <David.Herron@Sun.COM>]

Steve McKay☄ wrote:
> Hi All,
>
> I've noticed that at least some of the tests using java.awt.Robot are
> non-deterministic due to lags is the underlying window system. The
> java.awt.Component.keyPressTest, for example, fails some of the time
> (on linux, windows, linux+wine, ...). It looks like enabling
> autoWaitForIdle (waits for the awt EventQueue to be empty before
> adding new events to the queue), and setting autoDelay (pauses for an
> arbitrary period of time) to some magic number of millis well above
> zero (I use 100) significantly reduces failures. Would anyone object
> to configuring the Robot with settings like this by default? If no,
> should the config mechanism be updated to allow tweaking these
> settings?
>
>   

I don't know what the classpath implementation of Robot looks like, but 
I do know what Sun's Linux/Unix implementation looks like (having 
written the original version).

Generally Robot has to request the OS or X11 to synthesize the event.  
On Windows there's a direct API call, while on Unix/Linux there is a 
child process which ends up calling XTEST extension methods.  In both 
cases it means there is a nondeterministic delay due to the current 
process scheduling characteristics of the given system.  In other words 
it depends on an external entity, who Robot cannot coerce into 
performing the request within a bounded set of time.

I think that means depending on Robot doing it's thing within a given 
period of time is an invalid test.

Robot does not add events to EventQueue but it requests the OS to 
synthesize an OS-level event.

- David Herron