Using Kubuntu 16.04 on a Thinkpad X240 with Intel graphics this problem also causes Yakuake ("Quake-style terminal emulator based on KDE Konsole technology") to remain invisible when activated. It still accepts input and the window is in focus, it just is not visible.
Switching the compositor rendering backend from OpenGL to XRender works around the problem but the XRender backend seems to cause massive screen tearing when scrolling or watching videos so this workaround is suboptimal. Installing xserver-common and xserver-xorg-core from ppa:canonical-x/testing fixes the issue! -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg-server in Ubuntu. https://bugs.launchpad.net/bugs/1780664 Title: Recent libgl-mesa graphics update prevents drop down list menu appearing in apps like firefox three line/bar menu icon To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1780664/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp