Comment 41 for bug 365943

(In reply to comment #22)
> I can understand why two fingers would be used with the special button area.
> Why else would you use two fingers on a single-touch touchpad?
> Looking at the values my touchpad produces here, the ranges that I can trigger
> with by using two fingers and lifting one are about the same of those when
> moving fast from one point on the screen to another one.
>
> From an UI point of view, this is quite important: touching the touchpad with
> two fingers and having the cursor jump is a predictable response that can be
> avoided by using a single finger only. Having a threshold that cuts off certain
> movements can interfere with normal usage of the touchpad in a
> non-deterministic manner.
>

Users can (and do) accidentally put more than one finger on the touchpad, not only in the use case of the Synaptics Area. For example, if you use your index to move the cursor, it can happen that the middle finger (or another finger) accidentally touches the touchpad surface. On the Dell Mini10v and on some other netbooks when this happens the cursor jumps to the other side of the screen which is really not what I would call "predictable behaviour".

Of course on other models this problem is much less noticeable as in your case or on some other netbooks that I own. For this reason I think that we should adopt a case by case approach and apply the threshold only when the problem is unbearable.

I agree with you that cutting off movements is not ideal but in some cases it can really make a difference, which is why I'm more inclined to develop this as a quirk in the fdi file.