[webkit-dev] Do we need subpixel layout (Was: Should SATURATED_ARITHMETIC_LAYOUT be forced when enabling SUBPIXEL_LAYOUT ?)

Javier Fernandez jfernandez at igalia.com
Thu Aug 1 02:39:12 PDT 2013


On 01/08/13 00:26, Balazs Kelemen wrote:
> I think first we should clarify some more basic questions about subpixel
> layout.
> 1. Is it actually mantained?
> 2. Do any port really need it?
> Please correct me if these questions are too obvious or have been
> resolved before. Note that I am not a fan of subpixel layout, neither an
> enemy of it - in fact I do not know or care much about it. But from what
> I know it seems like this is a feature that makes an essential
> difference on the engine and I don't understand how can we allow such
> huge divergence across WebKit ports. Isn't it a maintenance burden?
> Doesn't it result in that test results across ports will diverge a lot more?

This is an important topic, since as far as I know, most of the ports
enable subpixel_layout by default. It would be good to know their future
plans on this regard.

IIMHO, just considering the theory, it looks like a nice feature to
have. Regarding whether is maintained or not, I see recent commits to
the LayoutUnit for adding subpixel support on some APIs.

Anyway, as I said before, I think the idea behind the
SATURATED_ARITHMETIC_LAYOUT flag to protect the LayoutUnit class against
arithmetic overflows looks like something we want anyway.


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