830406 - [Mac] entries in the list of Allowed Sites for add-on installation appear and disappear as the mouse moves over them

Status: NEW

(Core :: Widget: Cocoa, defect)

Description

[Jonathan Kew [:jfkthame]]

Attachment: the add-on installation exceptions list, with the first two entries displayed as blank

STR:
* Run Firefox with HiDPI rendering enabled on a Retina MacBook
* Open Preferences
* Go to Security panel
* Click the Exceptions button for Add-on installation warnings
* Move the mouse over the list of sites allowed to install add-ons

Result:
As the mouse pointer moves over the list of sites, the first couple of entries vanish and reappear more or less at random. (See screenshot, where the first two entries, addons.mozilla.org and getpersonas.com, are invisible.)

The entries always reappear after the mouse has left the area of the list.

This does not occur if HiDPI mode is disabled (gfx.hidpi.enabled = 0), so I'm guessing it is an invalidation and/or repainting issue related to hidpi coordinate conversions.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: the add-on installation exceptions list, with the first two entries displayed as blank

Better version of the screenshot, including mouse pointer.

Comment 2

[Jonathan Kew [:jfkthame]]

There's some weird interdependency here. The problem stops happening if I make the Exceptions window narrow enough that the introductory text ("You can specify which websites...") wraps onto three lines instead of two. It also stops if I make the window wide enough that the text fits on a single line. But at any width where the text occupies -two- lines (as it does by default), the problem shows up.

Comment 3

[Jonathan Kew [:jfkthame]]

Aha - it turns out this is NOT a HiDPI-specific bug. The same behavior - the first two entries in the Exceptions list disappearing "randomly" as the mouse is moved over them - can be reproduced on a non-HiDPI display, if the Exceptions window is enlarged horizontally so that the introductory text fits on a single line. (Compare the HiDPI case, where the problem occurs -only- when that text occupies -two- lines.)

The problem reproduces as far back as Firefox 14.0.1, but not on Firefox 13.0.2. So apparently something regressed in the Firefox 14 timeframe, though it went unnoticed because it doesn't occur with the Exceptions window at its default width. HiDPI mode just makes the problem more obvious because now it happens at the default width instead of with an extra-wide window.

Comment 4

[Jonathan Kew [:jfkthame]]

Bisecting with m-c builds shows that this regressed in the Nightly build of 2012-04-11.
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=7702bca6b64d&tochange=e636439e342f

Local build confirms that it was changeset 25a13d26509d (bug 733607) that triggers the problem.