207915 - position:fixed elements are incorrectly redrawn when the value of the display property changes

Status: NEW

(Core :: Layout: Positioned, defect, P3)

Description

[Vincent Lefevre]

User-Agent:       Mozilla/5.0 (X11; U; Linux ppc; en-US; rv:1.5a) Gecko/20030529
Build Identifier: Mozilla/5.0 (X11; U; Linux ppc; en-US; rv:1.5a) Gecko/20030529

CSS menus with position:fixed have some problems with positioning when the menu
contents disappear. Here's an example, which contains a menu with position:fixed
and a similar menu with position:absolute.

Reproducible: Always

Steps to Reproduce:
1. Open the above URL.
2. Move the mouse pointer over the first menu.
3. Move the mouse pointer upwards to make the contents disappear.

Actual Results:  
After 2, the menu flickers to the left but then it is correctly displayed. After
3, the menu is shifted to the right and the box is truncated.

Expected Results:  
One should get the same behaviour as with the second menu (position:absolute).

Comment 1

[Vincent Lefevre]

In fact, this is more than a display problem: When there are submenus, this bug
may render them inaccessible.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Looks like a layout problem (seeing this on Linux too).

Comment 3

[Anne (:annevk)]

Attachment: test case (from uri)

Comment 4

[Boris Zbarsky [:bzbarsky]]

This worksforme in a current build (likely as a result of widget change caching
and reflow before painting).  Vincent, are you still seeing this in current
trunk builds?

Comment 5

[Vincent Lefevre]

It seems to be partly fixed, but I still get a case with a strange behavior: by
replacing topleft by topright in <http://www.vinc17.org/cijml/index.fr.html> and
using the CSS menu (BTW, is it possible to ask Mozilla to produce a standalone
testcase?). Opera doesn't have the positioning problem seen with Mozilla.

Note: I've tried with Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b)
Gecko/20050114.

Comment 6

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 1 year(s).
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information