W3C home > Mailing lists > Public > www-style@w3.org > August 1997

Font Size discrepancies across platforms (was Re: Current Downloadable Font Status....)

From: Walter Ian Kaye <walter@natural-innovations.com>
Date: Sat, 23 Aug 1997 18:56:00 -0700
Message-Id: <v03102802b0253dec1b59@[]>
To: www-font@w3.org, www-style@w3.org
At 2:36p +0100 08/22/97, Clive Bruton wrote:
 > Todd Fahrner wrote at 22/8/97 5:15 am
 > >* As I can easily and amply demonstrate, points are a meaningless unit for
 > >on-screen type specification across platforms. I hear frequently that more
 > >than 60% of commercial web sites are designed on Macs, where 1 point is one
 > >pixel, regardless of real pixel density. Points specified in this
 > >environment will end up looking much larger most everywhere else, and in
 > >the opposite case text is often unreadably small for us Mac folk. Compare
 > >the screenshot referenced in your post (
 > >http://www.bitstream.com/world/screen.htm ) with the one I took of it on my
 > >Mac: http://www.verso.com/agitprop/truedoc/pointless.GIF . (Not only is the
 > >type 25%
 > >smaller in pixels, the GIF of the rendering is considerably smaller than
 > >the live TrueDoc data)
 > I'm not sure that I agree that a point is meaningless in this context, it
 > is an absolute rather than relative unit (ie screen res cannot be relied
 > on, so pixel based sizes will vary too), so would seem to give a better
 > starting reference.
 > I also think you got the scale factor back to front, if we accept that
 > Mac screen run at 72dpi (this is false - mine is running at just under
 > 100dpi, and there are other available that run in excess of 120dpi), and
 > PC screens run at some higher rate. 72pt = 72pixels on the Mac, 72pt =
 > either 72pixels (at a higher res) or n pixels where n=dpi of screen. So
 > PCs either see type at the same size or smaller than Macs, the exception

No, Windows displays type LARGER than MacOS. I just threw together a page:


A Windows 9pt font takes the same number of pixels as a Mac 12pt font.
This is because Windows *thinks* it is at 96dpi, while MacOS *mandates*
that it is at 72dpi. (ppi, whatever)

Even on the same platform, I think there is a lack in CSS. For example,
the following monospace MacOS fonts have the same character widths:

  Monaco 9/10, Courier 10, Courier New 10    (all 6px-wide chars)

  Monaco 11/12, Courier 12, Courier New 11   (all 7px-wide chars)

Is there a way to specify the above font-plus-size fallbacks, to preserve

 > being Macs that run higher res screens.

QuickDraw *ALWAYS* assumes 72dpi, and images fonts accordingly. Your video
configuration is irrelevant, as the OS has no idea how you manually adjusted
the analog amplification controls on your monitor.

 > The problem seems to be of the OS or the browser understanding what a
 > point is, and that screen resolutions are variable (therefore
 > compensating for that). Then everyone will get type the same size, but
 > with different resolutions (effectively different pixel per em values)

But how do you tell the OS what your video display LOOKS like? As far as
I know, there are no CRTs with any ability to sense their *true* geometry;
they only know if you increased or decreased something, and thus cannot
report the true/actual/visible/physically-measurable dpi back to the OS.

  Walter Ian Kaye <boo_at_best*com>    Programmer - Excel, AppleScript,
          Mountain View, CA                         ProTERM, FoxPro, HTML
 http://www.natural-innovations.com/     Musician - Guitarist, Songwriter
Received on Saturday, 23 August 1997 21:57:21 UTC

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