I am using a laptop with a HiDPI screen. Everything scales except for two apps. One seems to be GTK2 based and the other Qt5 based but where all the libraries it uses comes in the package (Viber for Linux. Both of them are basically useless since I can't see the written characters since they are too small. Is there anything I can do to get these two applications to scale like all my other applications do? I'm running straight Ubuntu 16.04 x64.
Try to invoke (run console by hitting shortcut
command before starting your application.
For me it works for some applications like Viber.
have you tried with unity tweak tool? try changing the font scale sudo apt-get install unity-tweak-tools just did it on ubuntu 16.04 and seems to be the final solution, tried many things (macbook pro retina 13)