Correcting inverted pan direction definition

Hey folks,
Looks like I made the classic mistake of thinking of scroll directions in
terms of finger/content movement directions instead of inverted (in one
place in the spec, not the other).  I've attempted to correct this with the
following wording but I'm sure it could use some more word-smithing.
Anyone want to propose something better?

" Directions are interpreted as the movement of the content relative to the
screen co-ordinate space, which is the inverse of physical finger movement
(drag down to pan up). For example, pan-right always corresponds to input
event sequences where screenX is decreasing at the start of a scroll."

We noticed this when Dave (cc'd) went to land the experimental
implementation in chromium.  We should have this available behind a flag in
canary builds within a few days.  Chrome Android now (finally) has a public
dev channel, so you'll be able to experiment with this on Android soon too.


---------- Forwarded message ----------
From: Rick Byers via GitHub <>
Date: Fri, May 8, 2015 at 1:58 PM
Subject: [pointerevents] new commits pushed by RByers

The following commits were just pushed by RByers to

* Correct inverted pan direction definition to match examples.

When we talk of "panning down" we generally mean the viewport is
moving down
relative to the content (increasing scrollTop values) which means the
content (and finger) is moving up relative to the screen.  I had this
in the non-normative examples I gave, but inverted in the formal
This CL fixes that and attempts to clarify the wording.
  by Rick Byers

Received on Friday, 8 May 2015 18:03:27 UTC