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

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Po Lu <luangruo@yahoo.com>
>> Cc: emacs-devel@gnu.org
>> Date: Sun, 26 Dec 2021 18:51:21 +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.

Thanks.