Comment 18 for bug 1780664

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!