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

Ryosuke Niwa rniwa at webkit.org
Fri Sep 6 13:12:08 PDT 2013

Thanks for the analysis!  Perhaps we should merge two build flags and turn
on the saturated arithmetic whenever subpixel is enabled.

- R. Niwa

On Fri, Sep 6, 2013 at 2:07 AM, Javier Fernandez <jfernandez at igalia.com>wrote:

> Hi,
> On 07/31/2013 10:40 PM, Ryosuke Niwa wrote:
> > Can't we encounter the same bug if we you multiplied the same height by
> > 64  even if the sub pixel layout is not turned off?  Or is there some
> > parser and other component that prevents such an overflow to happen?
> >
> I've been debugging and analyzing this issue a bit more and I concluded
> that the
> scenario described in bug 119273 is already protected if SUBPIXEL_LAYOUT
> is not enabled.
> The CSS max-height property value is clamped to max float during the
> parsing
> phase. Further arithmetic operations are already protected, so only the
> case of
> using the 64 factor defined for the SUBPIXEL_LAYOUT is still causing
> problems.
> So, this issue affects only the ports enabling SUBPIXEL_LAYOUT by
> default and
> not using the SATURATED_ARITHMETIC_LAYOUT. As far as I know, gtk+, Qt
> and EFL are the ports affected by this issue.
> Regarding the gtk+ port, the SATURATED_ARITHMETIC_LAYOUT would be
> enabled as soon as I verify bug 120583 is solved enabling this flag. Could
> anyone responsible of the other ports give some insight to this issue ?
> BR.
> --
> Javi
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