296025 - Rounding error with position:fixed top:0.5px

Status: RESOLVED FIXED

(Core Graveyard :: GFX, defect)

Description

[:Mook]

A div with position: fixed and top: 0.5px causes text within its border area to
be off by one pixel at certain text zoom levels.  Will attach testcase in a
moment.  (The text being affected is not structually within the div, it just
overlaps visually)

Probably related to tracking bugs bug 134942 and bug 63336

Tested on Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b2)
Gecko/20050530 Firefox/1.0+ (pacifica, 1.0+_2005053021/1.8b2_2005053021)

Steps to reproduce:
1. Open testcase
2. Change the text zoom level around.

Expected behaviour:
16 straight lines always.  (May be in 5 blocks depending on font)

Actual behaviour:
At some text zoom levels, the right half of some lines may be higher / lower
than the left half by one pixel.

Comment 1

[:Mook]

Attachment: test case

Only the position: and top: CSS rules are necessary to reproduce the bug; the
others are just formatting to make this easier to see.

Comment 2

[:Mook]

Attachment: screenshot showing problem

The lines should all be straight (as the top and bottom ones are), but some
lines (e.g. second from the top) is not and has a shift in it.

(Screenshot taken by banana in #firefox, who seems to be running Ubuntu's
Firefox "1.0.2" so it's probably a XP problem.)

Comment 3

[Aaron Slunt]

Probably related to 287624.

Confirmed Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b4)
Gecko/20050811 Firefox/1.0+ ID:2005081108

Comment 4

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

No, it's not.

Comment 5

[José Jeria]

WFM :Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20060126 Firefox/1.6a1

Bug 317375, comment 132 says that that bug fixed this.

Comment 6

[Steve England [:stevee]]

Testcase doesn't work with
Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.9a1) Gecko/20060124 Firefox/1.6a1 ID:2006012405
(back lines are not all lined up at different zoom levels)

Testcase does work with
Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.9a1) Gecko/20060126 Firefox/1.6a1 ID:2006012613
(back lines are lined up at different zoom levels)

--> RESOLVED FIXED (by bug 317375)