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

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Feb 28 18:48:52 PST 2007


------- Comment #11 from robburns1 at mac.com  2007-02-28 18:48 PDT -------
In reply to #10: Yes I know that a px is a relative unit and is allowed to
scale at high resolutions according to the CSS recomendation. However,
according to the expectations of Web designers and user-agent implementers it
is not. 

As you said in comment #3: "Web designerss assume 96dpi." This makes a relative
unit (one that is suppoed to be relative to the pixel resolution of a device)
no longer a relative unit. It is now precisely 96 dots per inch: it is locked
in a constant ratio with all the other absolute units. If a px is always 1/96
of an inch regardless of device resolution, then it's an absolute and not a
relative measure. That makes it an absolute unit as well. Any unit locked in a
constant ratio with the absolute units is an absolute unit. Obviously even the
absolute units are relative to the magnification level. Em and Ex remain
relative units. A device pixel likewise remains a relative unit. A CSS pixel
become just another absolute unit (which are all functionally equivalent
culturally different representations of the same absolute lenghts).

I don't see a problem with changing px to an abolute unit. Savvy content
creators know to avoid px because it's not really all that useful as a device
pixel. As this conventionally interpreted CSS pixel, it's just another absolute
unit. The same as using pts and multiplying by 1-1/3. But I just want to make
it clear (because from the discussion it doesn't seem clear) that this doesn't
obsolete the absolute measure. It eliminates the px measure as defined in the
recommendation (which the arms lenght and high resolution passages make fuzzy

Absolute measures: pt, pc, in, cm, mm, px
Relative meausers: ex em

Even the absolute measures are relative to display magnification (or the
positioning and zoom of a projector). Most modern displays change the
magnification level to less than 1x so that a phsyical ruler placed over the
software ruler (in say TextEdit) do not equal. It is not WYSIWYG in the size
sense that the term is (or was sometimes) used.

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