Dear Maintainer,

after upgrading to Iceweasel version 38.2.0 (previous versions of Iceweasel were working fine!)
there is a bug with Multi-Monitor setup and Iceweasel.


Bug Description:
Opening a popup menu (like the File Menu or Bookmark Menu) leads to opening the Menu on the
second screen while the iceweasel window is displayed on the first (primary) screen.

Expected is that the popup menu is displayed near the mouse pointer and near
the iceweasel window not on a completely different screen.


How to trigger:
Tracking down the bug reveals that it has to do with configuration of
option: layout.css.devPixelsPerPx

Setting the value of layout.css.devPixelsPerPx in about:config to a value
below 1.0 triggers the problem always! Even with a virgin iceweasel profile
and _NO_ add-ons installed, I tested this explicitely!

Setting the value of layout.css.devPixelsPerPx in about:config to a value
-1.0 or bigger than 1.0 prevents the bug, but iceweasels representation
of websites and the UI is way to large.


Remark:
* Setup of Multi-Monitor is done by:
xrandr --output eDP1 --primary --auto --output HDMI1 --auto --below eDP1
--dpi 85


Regards

src:iceweasel has been superseded by src:firefox-esr in version
45.0esr-1 in March 2016. Transitional packages to ease upgrades were
provided in the wheezy, jessie, stretch and buster releases. The
transitional packages have been removed finally before the bullseye
release in August 2021.
After regular security support for buster ended in August 2022 and LTS
support ended in June 2024, I'm closing the remaining bug reports now.

Andreas