[Webkit-unassigned] [Bug 11644] Absolute lengths assume 96.0 DPI

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=11644


robburns1 at mac.com changed:

           What    |Removed                     |Added
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                 CC|                            |robburns1 at mac.com




------- Comment #8 from robburns1 at mac.com  2007-02-28 15:01 PDT -------
I have to say that I don't have an easy solution to this problem, but I think
there appears to be a lot of confusion on this on both sides. The CSS
specification was quite ahead of its time in terms of resolution (and general
device) indepdendence. The OS world is just now catcfhing up with this.

With resolution indpendence successfully implemented, it is the px measurement
that becomes obsolute (not the absolute measures). Then a physical inch should
equal a screen inch (at least it should at the default magnification of most
displays). However, it's hard to imagine what role there is in this resolution
indpendent world for a pixel unit. By defining a pxel as 1/96th of an inch, the
pixel becomes an abolute unit (like the other absolute units always in the same
ratio). If an author does actually need a px unit (and I can't think of any
reason off of the top of my head), then it's no longer available. Perhaps a new
unit could be added ("pixel") that would still be available for that reason.

Take the iPhone display (160 dpi) or a larger and higher resolution display
(for example a future Cincema Display  at say 192dpi). There, since size is not
at a premium) the default magnification of the screen should be such that an
inch on the screen should equal a physical inch (therefore, likewise for all
the other absolute units). A px on that display is now 1/96 of an inch (2
device pixels). A display inch is equal to a physical inch (or it should be at
the default magnification). The iPhone display is a different story because
there's reason due to minmal screen real estate to change default magnification
from 1:1 (virtual:physical measurement).

So it's not the absolute measures that are usesless. It's the current px
measure that is becoming another absolute measure (1/96 of an inch). The other
issue is one of the default magnification of a display. Here I think it should
be 1:1 unless screen real estate is ilimited (as in the iPhone) or the audience
distant is great (as in TV or Projection media) However, the default
magnification is not something WebKit needs to worry about.  If there's a need
for a genuine pixel measure (a unit relative to resolution), then
implementations (and the CSs recommendation) could add something like "pixel".
Again, I can't imagine what use an actual resolution relative unit would serve.
Web designers have always been using it as an absolute measure (whether as 1/72
of an inch when the Mac graphical inteface arose or 1/96 of an inch when the
Windows graphical interface came of age). Those are absolute (though changing)
measures 


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