User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:48.0) Gecko/20100101 Firefox/48.0 Build ID: 20160824215626 Steps to reproduce: I am using Firefox 48.0.2 with gtk 3.20.9 with the i3 window manager. I am trying to drag objects (links, text, files from the download popup, objects from addons such as Zotero) out of firefox and then use a keyboard shortcut to switch to another window or workspace. (Similarly to alt+tab) Actual results: None of the keyboard shortcuts are working while dragging an object. Expected results: The keyboard shortcuts should have worked. Initially, I thought this was a gtk3 bug (https://bugzilla.gnome.org/show_bug.cgi?id=764605), but they marked the bug as fixed in version 3.20.4. The bug reports mentions a problem with xinput2. The suggestion is to start firefox with the environment variable MOZ_USE_XINPUT2=1. However, this does not change the observed behaviour.

Hi Mikan, I tested this issue on Ubuntu 16.04 with FF Nightly 51.0a1(2016-09-04) but I can't reproduce it, please note that I don't have i3 window manager and my gtk version is 3.16.7. Please create a new profile, you have the steps here:https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles?redirectlocale=en-US&redirectslug=Managing-profiles#w_starting-the-profile-manager Please test if the issue can be reproduced in the safe mode of Firefox: https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Also you can try to install FF Nightly 51.0a1 and retest it. https://nightly.mozilla.org/

To reproduce the bug you need to be on GTK 3.20. Using a fresh profile or nightly does not change the behaviour. However, after some more searching, I found this bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1276449