SWT, TypedEvent: how to make use of the time variable - swt

Question

The TypedEvent class has the member variable time. I want to use it to discard too old events. Unfortunately, it is of type int where as System.currentTimeMillis() returns long and both are very different, even when masking them with 0xFFFFFFFFL as the JavaDoc of time is telling me. How should the time be interpreted?

Answer 1

Note: As you haven't mentioned the operating system therefore I am safely assuming it as Windows (because this is what I have got).
Answer
If you closely look at the org.eclipse.swt.widgets.Widget class then you will find that TypedEvent.time is initialized as follows:
event.time = display.getLastEventTime ();
Which in return calls: OS.GetMessageTime ();
Now, SWT directly works with OS widgets therefore on a windows machine the call OS.GetMessageTime (); directly translates to Windows GetMessageTime API.
Check the GetMessageTime on MSDN. As per the page:
Retrieves the message time for the
last message retrieved by the
GetMessage function. The time is a
long integer that specifies the
elapsed time, in milliseconds, from
the time the system was started to the
time the message was created (that is,
placed in the thread's message queue).
Pay special attention to the line from the time the system was started to the time the message was created, which means it is not the standard System.currentTimeMillis() which is the elapsed time, in milliseconds, since 1, Jan 1970.
Also, To calculate time delays between
messages, verify that the time of the
second message is greater than the
time of the first message; then,
subtract the time of the first message
from the time of the second message.
See the below example code, which prints two different messages for time less than 5 seconds and greater than 5 seconds. (Note: It should be noted that the timer starts with the first event. So the calculation is always relative with-respect-to first event). Because of its relative nature the TypedEvent.time might not be suitable for your purpose as the first event may come very late.
>> Code
import java.util.Calendar;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.KeyListener;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class ControlF
{
static Calendar first = null;
public static void main(String[] args)
{
Display display = new Display ();
final Shell shell = new Shell (display);
shell.addKeyListener(new KeyListener() {
public void keyReleased(KeyEvent e) {
}
public void keyPressed(KeyEvent e)
{
long eventTime = (e.time&0xFFFFFFFFL) ;
if(first == null)
{
System.out.println("in");
first = Calendar.getInstance();
first.setTimeInMillis(eventTime);
}
Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(eventTime);
long dif = (cal.getTimeInMillis() - first.getTimeInMillis())/1000;
if( dif <= 5)
{
System.out.println("Within 5 secs [" + dif + "]");
}else
System.out.println("Oops!! out of 5 second range !!");
}
});
shell.setSize (200, 200);
shell.open ();
while (!shell.isDisposed()) {
if (!display.readAndDispatch ()) display.sleep ();
}
display.dispose ();
}
}