Bug 64036 – table cells with overflow clip should not trigger the slow painting path

• Status: RESOLVED
• Resolution: INVALID
• Component: Tables

[Julien Chaffraix]

Discovered while looking at some table profiling while scrolling.

Patch forthcoming.

[Julien Chaffraix]

Created attachment 99893 [details]
Proposed fix: don't hit the slow path if there is an overflow clip.

[Dave Hyatt]

Comment on attachment 99893 [details]
Proposed fix: don't hit the slow path if there is an overflow clip.

This is a false optimization. You can have visual overflow even when you have an overflow clip (for example via shadows).

[Julien Chaffraix]

Created attachment 100004 [details]
Test case generator

As discussed with David, here is my test case generator.

I invoke it like this:

./generate_table.py 500 500 > testCase.html

(Note the autogenerated HTML file is around 20M)

This generates a 500 x 500 table with random content and style. There is no possible overflow as we disable the overflow on each <td> but we still set the m_hasOverflowingCell on RenderTableSection which involves a lot of unneeded calls to RenderTableSection::paintCell.

[Julien Chaffraix]

Tried again today against the different generated test cases. I guess I must have been fooled by some caching and different versions of the generating script that did not have the "overflow: hidden" style.
It actually works well so just closing this bug, sorry for the noise.