1369847 - Thumb overshoots mouse position during press-and-hold on scrollbar track

Status: RESOLVED DUPLICATE of bug 1331390

(Core :: Layout, defect)

Description

[Botond Ballo [:botond]]

STR:
  1. Load a scrollable page, such as [1].
  2. Click on the scrollbar track, away from the thumb,
     holding the mouse down until the thumb stops moving.

Expected results:

  When the thumb stops moving, it's under the mouse.

Actual results:

  When the thumb stops moving, it has overshot the mouse
  position and is no longer under the mouse.

This was tested on Windows. On Linux, press-and-hold has a different behaviour (the thumb keeps going until the end of the scroll range), although inverting the condition of this #ifdef [2] causes Linux to have the Windows behaviour (including the bug).

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1321428
[2] http://searchfox.org/mozilla-central/rev/972b7a5149bbb2eaab48aafa87678c33d5f2f045/layout/xul/nsSliderFrame.cpp#1432

Comment 1

[Botond Ballo [:botond]]

Mozregression came up with this regression range:

https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=daa84204a11a&tochange=dc352a7bf234

In that range, bug 957445 seems the most likely culprit. Kip, you are assigned to that bug, do you think it may have caused this?

Comment 2

[Botond Ballo [:botond]]

Oh, it looks like bug 1331390 is already on file for the same issue.