W3C home > Mailing lists > Public > www-style@w3.org > December 1998

Re: platform-specific font size issues

From: Chris Lilley <chris@w3.org>
Date: Tue, 15 Dec 1998 22:50:05 +0100
Message-ID: <3676D98D.B937D1A1@w3.org>
To: Todd Fahrner <fahrner@pobox.com>
CC: www-style@w3.org

Todd Fahrner wrote:

> The current default of 12pt rasterizes very differently across platforms.
> On Macs, it rasterizes into 12px (logical res fixed at 72ppi).

Which is dumb because you can use a good 17inch monitor at 1600by1200 to
get high quality digital soft-proofing of images for magazine work (for
example) which gives around 150 dpi. On a Mac.

>  On Wintel
> PCs, it rasterizes by default into 16px (logical res defaults to 96ppi). I
> am unfamiliar with X11 default behavior(s). 

The X server exposes the width and height of the display (in
millimeters) and the height and width (in pixels) and thus the
resolution, which is not fixed at 72dpi.

> The appropriate corrective measure, I submit, is for Mac (and X11?)
> browsers to break with tradition and ship with the default value of
> "medium" text set at 16px, instead of 12pt. 

That will be much easier to do once browsers really do use a CSS
stylesheet as their browser default stylesheet, and once the hard-coded
presentational hacks go away.

> 2. The 1996 CSS1 standard suggests a 1/90" value for a "reference pixel",
> extrapolated from a visual angle of 0.0227 degrees visual angle at arms
> length. UAs are expected to scale pixels appropriately if the physical
> resolution is known to vary significantly from this value. A 1/90"
> reference pixel would suggest a rasterization of 12pt into 15px, rather
> than 16. 15 is of course much closer to 16 than to 12, however. Because no
> OS/UA currently assumes a 90ppi logical resolution,

Actually, yes. In fact, if you do an xdpyinfo command (which gets the
dots-per-inch of the current X display on Hakon's Sun workstation, guess
what value you get?

>(nor implements
> pixel-scaling per CSS1), 

Most printers implement it, because (in a world of inexpensive 720 dpi
inkjets) the consequences of not doing so are not acceptable to even the
most accepting of Web users.

> I think the reference pixel value should be
> amended to 1/96". It's simple to preserve the suggested 0.0227 degrees
> visual angle by giving the reference user a longer arm's length. (^:

Ah yes, the foot was originally the length of which English monarchs

I guess if you twisted Hakons arm it would serve two purposes: a) make
him tend to agree, and b) lengthen his arm in case he did not agree.

As to your suggested change in the Mac browsers default stylesheets,
well I will let the design teams of the Mac CSS-implementing briwsers
speak about that themselves.

Received on Thursday, 17 December 1998 12:09:51 UTC

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