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Re: Firefox Font Rendering



On Thu, 2008-10-30 at 20:31 +0100, David Hláčik wrote:
> how come Firefox does not change font-size when changing DPI in Gnome Settings?

Properly, it should not.  But it doesn't, for another reason.  It
handles font rendering itself, so uses it's own setting.

The reason that it should not change font *size*, is that's a completely
wrong, though commonly implemented approach.  (Nor should anything else
behave that way, either.)

Changing DPI should change the resolution of the font (how many dots are
used to draw it very smoothly, or less so).  And other parameters which
state the physical screen size and the number of pixels, *should* be
used in combination to determine the actual font size.

So many things get this utterly wrong, and completely screw up proper
font handling (and other drawing issues).

http://kb.mozillazine.org/Layout.css.dpi  gives some information about
how to mess with DPI in Firefox, but it makes the classic blunder of
talking about *printing* a pixel based font size, then says it'll be X
big regardless of actual printer resolution.  

Umm, NO!  Pixel based sizing WILL and SHOULD be dependent on the number
of pixels available, despite the problems with that, other sizing
schemes are the absolute sized ones.  This is a broken behaviour to
accommodate people who don't know what they're doing, who specify pixel
based sizing inappropriately.

Don't understand resolution?  Get some graph paper, with two different
sized grids.  Draw a circle, or other shape, that's 5 cm wide.  Now fill
in the squares where you've drawn through.  That's resolution - the dots
that you can actually make *use* of.  The dots that are there, even if
they're too tiny for you to distinguish - the point that you can
distinguish the dots is another issue, not resolution, but "definition".

The reverse approach involves calculating things so you know how many
dots to draw to get something the right size.  The size being the
initial drawing parameters, not the pixels.

There's three aspects to drawing on a dot based medium:  The size of the
medium, the number of dots it can use (e.g. 1080 by 800), and the
calculation of the number of dots to be used when you want an object of
a certain size.  Just about everyone does the last stage the wrong way
around.

-- 
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