221007 - Missing right border at certain widths when left and width is percentage based

Status: VERIFIED DUPLICATE of bug 176237

(Core :: Layout: Positioned, defect)

Description

[Richard Aspden]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5; MultiZilla v1.5.0.2j) Gecko/20030925
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5; MultiZilla v1.5.0.2j) Gecko/20030925

When Mozilla is resized, or sized to a certain width, random loss of the border
occurs, with the issue getting worse upon scrolling. One such width appears to
be a 797 pixel browser render area. (Could be wrong, I was using PSP and
cropping to find out!)

Bug verified on builds 20030925 (RC-2) and 2003092704.

Reproducible: Always

Steps to Reproduce:
1. Resize the window

Actual Results:  
Watch the borders mysteriously vanish until you resize to another width.
Scrolling up and down enhances the problem.

Expected Results:  
Rendered correctly and not lost the border.

I'm not sure if this is related specifically to Windows, but I've noticed it
repeatedly. We're using a pure CSS and XHTML 1.0 <div> based layout, with no
tables etc at all. Verified on 3 seperate machines.

Comment 1

[Richard Aspden]

Attachment: Screenshot of bug

Screenshot showing the missing border on the page in question.

Comment 2

[Kai de Leeuw]

This page looks completely different in IE6. Are you sure you haven't done
something illegal that makes mozilla behave unexpectedly?

Also, could you provide a minimized testcase? That is, minimize the webpage
until only parts relevant for the bug remains? Often this is a good strategy for
the web page developer to pinpoint if a bug indeed is a bug and to pinpoint what
makes the "error" in layout appear.

Comment 3

[Boris Zbarsky [:bzbarsky]]

This is a known issue with very thin borders and a mix of px and em units --
rounding errors can cause the border to not be painted...

Comment 4

[Richard Aspden]

Re IE6: Seems that when I cut some of the data out, it broke it. I'll try to get
a minimal testcase shortly.

Re the very thin borders and mixing em/px borders - we only ever use px borders,
although those particular ones are 1px. I've seen this issue before, but will
try to create it in the minimal format ASAP.

Comment 5

[Richard Aspden]

Attachment: Minimal testcase

Reduced to it's bare minimum.
The height of box seems to affect it, as soon as the box extends below the
screen at certain widths, the right border disappears. It's important that it
extends past the bottom of the screen though, otherwise the behaviour doesn't
occur.

Comment 6

[Mats Palmgren (inactive)]

Confirming bug, 2003-10-02-05 trunk Linux.

Bug only occurs when 'position' is 'relative' or 'absolute' and
'left' and 'width' both are percentage based.  As already noted, it only
occurs when the bottom of the box is outside the view.  It seems it's not
triggered by the scrollbar per se because forcing a scrollbar with a bunch of
<br>'s did not trigger the problem alone.

Bug also occurs in 1.5rc1 and 1.4 with the same symptoms as described above.
Bug also occurs in 1.3.1 but here it occurs at all view heights, even without
a scrollbar.
Bug does NOT occur in 1.0.2

Comment 7

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

There was a reason for the "DUPEME" in the status whiteboard.

*** This bug has been marked as a duplicate of 176237 ***

Comment 8

[Mats Palmgren (inactive)]

Oops, my bad.  I didn't find that because it was filed on GFX - it seems to
me this a rounding problem somewhere inside the Layout code?

Verified dupe