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 18:58:50 +0800
> 
> >> DX and DY are represented in an imaginary unit where 1.0 is the
> >> horizontal width and vertical height of the touchpad (or more precisely,
> >> depedent touch device, which might include Wacom tablets if their
> >> drivers are configured in a special way) respectively.
> 
> > This should be documented.
> 
> Yes, I'll do that.
> 
> > But I wonder how these two values are useful, if their units are not
> > pixels and not anything that can be converted to pixels?
> 
> You are supposed to multiply it by the dimensions of whatever object is
> onscreen: in image-mode, it could be the dimensions of the image, while
> in a message buffer it could instead be the dimensions of the window's
> text area.

But you said above that the value 1.0 is the size of the touchpad, not
of the image or text window?  So now I'm confused.