screen physical size, DPI, font size - how does it work?

[Felix Miata]

On 2007/10/08 10:43 (GMT+0800) Hong Liu apparently typed:

> I am also looking at this problem recently. Problems are if we can't
> detect the physical size from EDID data, X server calculates the
> physical size using 96dpi.

This would be nice if the actual screen DPI is at or near 96. It's very bad
when the screen DPI is high, like 108 or 120 or 144 or more, and not so good
when the DPI is 84 or less either.

> Or we get wrong physical size from EDID data,
> and this may cause X server get wrong DPI.

This happens to me frequently, as I have multiple displays with no EDID and
bad DDC.

> Currently we don't use the DisplaySize option to override the physical
> size of monitor. I am not sure preferring user specified physical size
> is a feasible solution?

What other option makes any sense? Is it so hard for a user to find a ruler
and measure his screen when DDC and EDID don't work? In some cases, the
display dimensions are in an installation database, and the installation tool
looks it up and puts it in xorg.conf. Why should use of DisplaySize be any
different now and in future than it used to be?
-- 
"The basis of our Bill of Rights comes from the teachings
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 Team OS/2 ** Reg. Linux User #211409

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