bug#66308: 30.0.50; DocView: Bump default value of doc-view-resolution

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Stefan Kangas <stefankangas@gmail.com> writes:

> How about increasing the default value of `doc-view-resolution' from 100
> to something like 300?  In my use, I find that the default value gives
> poor results, especially after `doc-view-enlarge', whereas a value of
> 300 gives a nice, crisp display.  Monitors these days are certainly much
> larger, and have much higher resolutions, than they used to.
>
> People in highly restricted environments might have to turn it back down
> again, of course.  I think this is okay though, if the benefit is that
> doc-view will look better in more typical cases.
>
> I also note that `doc-view-resolution' has had the same value since
> 2007, when DocView mode was first added to Emacs.  After 15-20 years, it
> might be time for a bump.

How about making the resolution commensurate with that of the display
itself?  Monitor density has not increased for lay folk, only those
willing to spend prodigally on display hardware.

Compounding that, larger images will consume greater quantities of disk
space and X server memory.  Bear in mind that /tmp is customarily small;
only 4 GiB on my system, with 1.8GiB in use, whereof /tmp/docview1000
consumes 971 MiB.