224309 - border-collapse:collapse tables limit border widths to 63 pixels

Status: RESOLVED FIXED

(Core :: Layout: Tables, defect)

Description

[Randeep Walia]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.5) Gecko/20031007 Firebird/0.7
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.5) Gecko/20031007 Firebird/0.7

When using large table border definitions in my CSS sheet, any border greater
than 63 pixels will disappear. As the border is not visible, it still seems that
HTML elements are 'pushed in' by the appropriate amount, however, once you start
using really large borders (100s or thousands of pixels) behavior becomes
erratic and unpredictable.

Reproducible: Always

Steps to Reproduce:
1.Open/save the attached file
2.View in browser
3.Experiment with changing the CSS table border value to see different results

Actual Results:  
Table border stopped rendering after width was made greater than 63 pixels. Very
large borders rendered erratically.

Expected Results:  
Mozilla should have renedered the appropriate border visibly with the specified
width on the left, right, top and bottom edges of the table.

See following attachment HTML and images.

Comment 1

[Randeep Walia]

Attachment: Example 64px border HTML Table

This HTML defines a table with 64 pixel width. Turning the border to 63
'switches' the solid black border on (as a side note, using a 63 pixel or other
sizeable border may cause black lines to appear inside of the table when
scrolling via keyboard or mouse. This error is already defined in bug 111176
and should be ignored for this test case).

Comment 2

[Boris Zbarsky [:bzbarsky]]

The problem is that the BCData struct (which stores sizes of borders in
border-collapse mode) only allocates 6 bits for storing the width (in px).  So
for borders larger than 63px, the data type overflows and things break.

This struct should probably be converted to not be so bitfield-happy....

Comment 3

[Bernd]

I discussed that with Chris when he introduced this limit, we couldnt spot a
single case where real pages use borders larger then 63 pix. Changing the bc
code to have table cell based painting would lift the limitations.

Comment 4

[Randeep Walia]

I'm sure it's currently a rarity to have a border greater than 63px, but as
CSS-based layouts become more common I think you'll find that it will come up in
design more.

Comment 5

[Boris Zbarsky [:bzbarsky]]

*** Bug 254554 has been marked as a duplicate of this bug. ***

Comment 6

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

Fixed by checkin of bug 286794.