1272084 - Autoscrolling should not work for overflow:hidden scroll frame

Status: NEW

(Core :: DOM: UI Events & Focus Handling, defect)

Description

[Botond Ballo [:botond]]

STR:
  1. Load http://people.mozilla.org/~bballo/hidden.html
  2. Autoscroll (that is, scroll the page by clicking the
     middle mouse button and moving the mouse).

Expected results:
  The page is not scrolled, since it's marked overflow:hidden

Actual results:
  The page is scrolled

This behaviour is unrelated to APZ, and has been in place since at least Firefox 44.

Comment 1

[Markus Stange [:mstange]]

The element whose scrollTop autoscroll changes is the html element, but this page sets overflow:hidden on the body element. Doing that triggers magical behavior inside Gecko to propagate the overflow to the html element, but autoscroll doesn't know about this magical behavior.

Comment 2

[Markus Stange [:mstange]]

I was wrong, overflow:hidden is on both the html element and on the body. Ignore comment 1.

Comment 3

[Andrew Overholt [:overholt]]

(In reply to Botond Ballo [:botond] from comment #0)
> This behaviour is unrelated to APZ, and has been in place since at least
> Firefox 44.

So it's a regression?

Comment 4

[Botond Ballo [:botond]]

I tested as far back as Firefox 19, and the behaviour has been the same since then. Firefox 18 and earlier either won't run at all or are completely unusable on my system, so I couldn't test with them.

So, this is most likely not a regression. It's always been broken.

Comment 5

[Andrew Overholt [:overholt]]

Bug 1259357 has issues with mouseup events in overflow:hidden; maybe related?