Bug#988135: evince: zooming 100% ignores dpi as reported by xrandr

[Helmut Grohne]

Package: evince
Version: 3.38.2-1

When you zoom a document to 100% and hole an equally sized sheet of
paper on the screen, you expect them to match. That used to be the case
with evince, but it no longer does. I don't know precisely since when.

Usually, xrandr/xdpyinfo know both the logical (pixel count) and
physical (mm or inch) dimension of the screen. From those values, one
can derive a dpi value to adjust what 100% zoom means. Applications such
as djview still implement that.

It seems like evince chose to change that:
https://sources.debian.org/src/evince/3.38.2-1/libdocument/ev-document-misc.c/?hl=552#L562

The logic there essentially says: If your screen is taller than 1080
pixels in landscape, your dpi is 192 and otherwise it is 96. For a
typical 1900x1200 24" display that happens to have roughly a dpi of 96,
evince determines that it must be a HiDPI display at 192 dpi. As a
result, 100% actually presents more like 200%.

That's quite unhelpful. This used to work correctly.

Helmut