[webkit-dev] Should SATURATED_ARITHMETIC_LAYOUT be forced when enabling SUBPIXEL_LAYOUT ?

[Javier Fernandez]

Hi,

While looking into the bug #118595 I've found out that the root cause
was an arithmetic overflow during the layout process, at least in the
case of the WebKitGtk+ port, but I guess other ports have similar root
cause. Notice that webkitgtk+ port enables the SUBPIXEL-LAYOUT by default.

Later, I've concluded that the bug is not related to Regions at all, but
something generic happening when the max-height CSS property value is
set to a huge number. I've filled a new bug #119273 for this.

The arithmetic overflow is gone when enabling the
SATURATED_ARITHMETIC_LAYOUT flag, which actually, as far as I could
understand, it's the purpose of such experimental feature.

However, I've provided a patch for the #119273 facing the specific case
of the max-height. I don't think that's the right approach, because I
think other CSS property might have the same problem, but I thought it
was useful to understand the issue.

I think the right solution would be to enable the
SATURATED_ARITHMETIC_LAYOUT whenever the SUBPIXEL_LAYOUT flag is
enabled. Perhaps, eventually, both flags will become part of the same
feature; that's one of the points to be discussed here.

I'm sending this email to this list in order to get an agreement between
all the ports using the SUBPIXEL_LAYOUT feature, but perhaps this should
be debated independently on each port's mailing list.

Regards,

--
Javi