Re: X server latency

["Elijah Newren" <newren gmail com>]

Hi,

On 4/17/07, Rachid KHAZAZ <rachiddelta yahoo fr> wrote:
> I have two questions :

You have stumbled across the wrong list.  ;-)  This list is about
standards for communication between window managers, specialized pager
apps, and applications.  It isn't for questions on how X work and
writing Xlib applications.  Since the list is relatively low volume I
will include a quick explanation to your two questions, but please
take any further questions about how X work elsewhere.

Cheers,
Elijah

> 1) I have written a program (see the attached file) that displays the x
> coordinates of the pointer when the MotionNotify event is catched.
> When moving the mouse very slowly, the coodinates shown like
> 150,149,148......
> But when I move the mouse very quicly, the coordinates like 150, 125, 80....
> How do you explain the difference between the two sets of results.

The granularity of motion events is not guaranteed, but a client
selecting for motion events is guaranteed to get at least one event
when the pointer moves and comes to rest.

> 2) I have written an X client which moves the pointer by XWrapPointer()
> function, when executing this program and the program of 1), the last one
> doesnot detect the pointer motion caused by the XWrapPointer(). Do you have
> an idea about that? and how can i produce the detection of a "simulated"
> mouse motion.

I would guess that your XWarpPointer() call is moving the mouse into a
new window entirely.  MotionNotify events are only generated when the
motion begins and ends in the window.  If pointer motion causes the
pointer to be in a different window than before, EnterNotify and
LeaveNotify events are generated instead of a MotionNotify event.