[thelist] front end design: liquid design

Felix Miata mrmazda at ij.net
Thu Oct 30 09:09:45 CDT 2008

On 2008/10/30 05:58 (GMT-0700) Mark Groen composed:

> On Wednesday 29 October 2008 21:59:50 Felix Miata wrote:

>> I don't know what you mean. High DPI is an environment. Properly designed
>> user agents simply use whatever DPI everything else in that environment
>> uses.

>> 1-On a modern Mac, DPI is locked at an assumed 96, regardless what the real
>> DPI is.
>> 2-On Windoz, the traditional default is an assumed DPI, regardless what the
>> real DPI is,

> It is not an assumption, the W3C calls as a reference the 96dpi figure:

> http://www.w3.org/TR/CSS21/syndata.html#pixel-units

> If the pixel density of the output device is very different from that of a 
> typical computer display, the user agent should rescale pixel values.

> Which the smaller screens/user-agents (such as an iPhone) set with a higher px 
> density do, and quite well too (imho). IOW, use px, ems, or % - they are all 
> relative units.

> It is recommended that the reference pixel be the visual angle of one pixel on 
> a device with a pixel density of 96dpi and a distance from the reader of an 
> arm's length.

That same W3 page does also claim px is a relative unit. Both claims have big
problems. The CSS px is relative to the viewing device. That is an irrelevant
relativism as long as the CSS px in real world practice on desktop operating
systems never gets scaled (as long as the CSS px and the device px are
equivalent), either by the UA or the OS environment. The latest Gecko
browsers do have a crude CSS px scaling capability, but it doesn't go into
effect until reaching a threshold that is twice the assumed 96 standard.
Neither are expected to change from their current conditions for the
foreseeable future.

Later that page says "Absolute length units are only useful when the physical
properties of the output medium are known." Because device px density is
always unknown to designers/developers, and CSS px in practice is exactly
equal to device px, px would be better categorized as an absolute than as a
relative unit, but would be better still categorized as neither.

It boils down that the only relevant relatives in CSS are the em and the ex.
Fortunately they can work, if only more than a token number of developers
would use them for something besides arbitrarily shrinking most text from
whatever user preference sizes happen to be.
"Everyone should be quick to listen, slow to speak, and
slow to become angry."		James 1:19 NIV

 Team OS/2 ** Reg. Linux User #211409

Felix Miata  ***  http://fm.no-ip.com/

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