Re: DPI, font size, and Debian

[Billy Biggs <vektor@dumbterm.net>]

Simon Law (sfllaw@debian.org):

> > I disagree.  If I hook my laptop up to a data projector, I do not
> > want all of my fonts to shrink to nothingness.
> 
> I think that the data projector would have to lie about its DPI.  It
> doesn't even make sense for a data projector to tell anyone about its
> DPI.  It certainly doesn't know.

  Agreed. :)

> >   I believe that:
> >     - "Screen DPI" as a concept is really just a "scale factor" for user
> >       interfaces and should almost never represent the literal meaning
> 
> Screen DPI is actually meant to mean exactly that.  If you want a
> scale factor, this should be set somewhere else, since this is a
> different concept.  That way, if you want all your widgets super big
> because you have bad vision, even if you switch monitors, they will
> stay exactly the same size.

  This is exactly what I am proposing, basically.  Screen DPI today is
meaningless on Windows because they use it as a scale factor,
meaningless on MacOS because it is always 72, and meaningless on Linux
because it is set basically randomly unless someone manually figures it
out.  If you want a DPI setting that is correct, but must always be set
manually, fine, use DPI.  But please set it to something sane as a
default!

> >     - Many fonts design their hints for specific point sizes at specific
> >       DPIs.  Using "99x98" DPI or "102x102" DPI, even if accurate, is
> >       not productive.
> 
> Hrm...  I always thought that since fonts were hinted algorithmically,
> the minor differences between those DPIs would be indistinguishable.  I
> didn't know that hinting engines are that fragile.

  I should probably be making this case stronger.  I put up a webpage
with some screenshots that shows the effects of having "close, but not
as intended" DPI values:

  http://scanline.ca/dpi/fonts.html

  -Billy