Resolution indpendence

[Glynn Clements]

olafBuddenhagen at gmx.net wrote:

> First of all, we do usually have two information points: Resolution and
> display size. From these, I think we can make a pretty good guess at the
> viewing distance/angular resolution -- no need for an enormous database.

You can make a guess, and you don't need a database. But you do need
to allow the user to override your guess.

> For one, while I do not agree with Glynn that for today's typical
> resolution it's *only* the pixel grid matters,

I never said that.

That was an attempt at misrepresentation by someone who was arguing
that it's *only* the physical size which matters. They appear to have
succeeded.

For me, with the monitors which I use and with my eyesight, the pixel
grid is typically the limiting factor. On my primary monitor, the
minimum physical size and the minimum pixel size both dictate the same
font (12-pixel adobe-courier, which is actually 7x13). On monitors
with lower dpi (which I use quite often), I need to keep the same
pixel size (larger physical size) to retain legibility. If I had a
monitor with higher dpi (I don't), I would probably need to retain the
same physical size (larger pixel size) to retain legibility.

For someone with poor eyesight and who only uses good (high-dpi)
monitors, it's likely that the pixel grid will never be a factor. For
someone with reasonable eyesight and a poor (low-dpi) monitor, the
pixel grid may always be the limiting factor.

> The bottom line is that finding the effective resolution involves many
> parameters, which all have nonlinear effects. Yet the result is a
> relatively simple two parameter function on display size and resolution.
> Starting with a number of data points found by experiment, it should be
> possible to fit a function that pretty well models typical user's
> expectations about effective resolution.

Any calculation based solely upon physical dimensions and pixel
dimensions is going to be a starting point at best. You cannot
determine the user's visual acuity and, at least initially, you cannot
determine the priority which they attach to text density.

If someone is using primarily graphical applications, where the only
text is the UI (menu bar, status bar etc), using a larger font isn't
going to significantly affect the amount of information they can get
on screen (i.e. the size of the application's "canvas").

OTOH, if someone's primary application is a text editor, a 20% larger
font will result in 20% fewer lines (and columns) of text on screen. 
Consequently, they are more likely to care if you choose a font which
is any larger than is strictly necessary.

-- 
Glynn Clements <glynn at gclements.plus.com>