W3C home > Mailing lists > Public > public-houdini@w3.org > February 2015

Re: Font Metrics concerns

From: Chris Lilley <chris@w3.org>
Date: Sun, 8 Feb 2015 04:52:58 +0100
Message-ID: <145105640.20150208045258@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Alan Stearns <stearns@adobe.com>, "public-houdini@w3.org" <public-houdini@w3.org>, John Daggett <jdaggett@mozilla.com>, Bram Stein <stein@adobe.com>
Hello Tab,

Sunday, February 8, 2015, 3:55:38 AM, you wrote:

> On Sun, Feb 8, 2015 at 1:45 PM, Alan Stearns <stearns@adobe.com> wrote:
>> The TextMetrics interface has attributes for some of these metrics in CSS
>> pixel units. This makes sense for the canvas measurements being made by
>> that interface, but I’m thinking the font interface we’re designing should
>> be expressed in more abstract units. One possibility is to add a
>> unitsPerEm attribute and express all the other metrics in those
>> font-specific units. That’s probably the most natural thing to do for
>> typographers. But I think it could also work to rationalize on a single
>> unitsPerEm value or use an em percentage.

> An em percentage is fine with me.  No need to indirect through some
> variable amount of units.

I think that people with a type background are going to want to use
the units for their preferred font format (so 1000 or 2048, in
practice) and will resent having to mentally convert to em percentage
when they normally think in other units.

So values in units, together with units-per-em (like the descriptor),
is a better method for the intended audience. This can also be
expressed as a percentage, for people who are comfortable with that.

Best regards,
 Chris Lilley, Technical Director, W3C Interaction Domain
Received on Sunday, 8 February 2015 03:53:00 UTC

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