Re: master 101bbd1392: Add support for pinch gestures to the XI2 build

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Sun, 26 Dec 2021 18:03:31 +0800
> 
> >>                                       @var{dx} is the distance between
> >> +the horizontal positions of the fingers since the last event in the
> >> +same sequence, @var{dy} is the vertical movement of the fingers since
> >> +the last event in the same sequence,
> >
> > What is the meaning of "the distance ... since last event"?  Did you
> > mean the _change_ in the distance since the last event?  And anyway,
> > what does "last event" mean in this context -- this is not explained
> > anywhere.
> 
> I tried to explain what a sequence is later on, and yes, I meant the
> change in distance.

I tried to fix this in a followup change.  But now I wonder if I
understood the semantics correctly:

> + All arguments after @var{position} are floating point numbers.

Does this mean DX and DY are also floats?  If so, are they in pixels
or are they some kind of relative change?  If they are relative, then
relative to what?  And why does text-scale-pinch require that both DX
and DY be zero?