Bug 291405 – perf issues with rowspan="0" on huge complex tables

• Status: NEW
• Component: Tables

[Karl Dubost]

Created attachment 474888 [details]
simple table 3x3 no rowspan

In Bug 185341, the layout for rowspan="0" was fixed.
It is working well for simple table but creates performance issues for huge tables with weird and incorrect rowspans. 

It needs to be improved.

[Karl Dubost]

Created attachment 474889 [details]
simple 3x3 with rowspan 0 in the first column

[Karl Dubost]

Created attachment 474890 [details]
rowspan=2 testcase

[Karl Dubost]

Created attachment 474891 [details]
rowspan=0 not removing cells

[Karl Dubost]

Created attachment 474892 [details]
rowspan=2 with two tbody

[Karl Dubost]

Created attachment 474893 [details]
15x3 table with many rowspan

[Karl Dubost]

Created attachment 474894 [details]
93 rowspans

This one displays but starts to be slow. 
It has 4 lines with 93 rowspan of different natures with different columns. 
It's where the complexity starts to kick in.
It displays faster in Chrome/Firefox (but probably also slower than expected.)


I have a patch which improves the speed.

[Karl Dubost]

Created attachment 474895 [details]
1381 rowspans of different nature with complex tables

Some cols and rows are different
There are 1281 rowspans on 62 rows with 1746 cells 

41 rowspan="1"
20 rowspan="2"
1319 rowspand="0"
366 cell without rowspan 

This is crazy but this has hit a real case not accessible on the public web. 

The layout doesn't really make sense. 
BUT Firefox and Chrome managed to display it. 

This will freeze Safari 18.4

[Karl Dubost]

<rdar://146056348>

[Karl Dubost]

Pull request: https://github.com/WebKit/WebKit/pull/43940