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.