Settng DPI on gdm and Sessions

[Tom Horsley]

On Tue, 19 May 2009 17:48:14 -0700
Adam Williamson wrote:

> ...and anyone who ever, say, prints anything.

Printing has absolutely nothing to do with viewing display
devices. Precise dimensions are important on printed media
for filling out forms, getting inside label boundaries, etc.
None of those reason apply to display devices. What you do
want on a display device is to see the same proportions
to know how it will look when you print it, but same proportions
are nothing at all like same absolute size.

> Ironically, that's exactly what resolution independence is intended to
> achieve.

Not the way you define it. A 9 point font is perfectly readable on
a piece of paper I'm holding in my hand. On a 1920x1080 42" HD
monitor, lower case characters rendered in a 9 point font have
about 4 pixels available to render the character. It does me
absolutely no good to have the size be "correct". All I get
are little indistinguishable blobs.

Lying about the DPI scales everything up so that the image
of the characters on the screen has just about the same angular
diameter from my viewing location as the printed characters
on the page in my hand.

Unless I'm trying to read a secret message revealed by laying
a piece of tracing paper on the screen to complete an image
partially printed on the paper, I can't imagine any use for
forcing screen DPI to be physically "correct".