On Linux Mint Cinnamon 18, Kdenlive using Gtk+ style, regards of the theme, the Tooltips show in yellow background and white color, it's impossible to read to them. Using style Breeze, there is no problem, but look and feel it's not the same has other Mint programs. Reproducible: Always Steps to Reproduce: 1. Style -> Gtk+ 2. Hover on tool icon Actual Results: Tooltips show in yellow background and white color Expected Results: Tooltips with a color that can be read using a yellow background.
I'm afraid we can't help here, as this is an KF5/Gtk+ integration issue, thus upstream. Can you please check your desktop color scheme? Can you also check with your distro packagers for how KF5 apps should work with gtk styles? Thank you very much for your cooperation!
On other programs like GIMP or LibreOffice using Gtk+ it displays yellow background with black color, which is perfect for reading. I'm using Linux Mint 18 with the default color style. I checked more programs running Gtk+ and all have a black tooltip color, only Kdenlive shows white color using Gtk+ style. Is it possible to force the black color on Gtk+ for the tooltips?
The GTK+ style is poorly supported because it does not allow customizing colors. You can however solve the issue by installing the "gnome-color-chooser" package. Open the application, and under the "Specific" tab, you have an option to force Tooltips colors. In my tests, changing Foreground color does nothing, but you can set the background color to something dark and it fixes the kdenlive tooltips.
Thanks. I installed gnome-color-chooser, and found a background color that is readable with white and black foreground, since as you mention changing the foreground as no effect. This all the other programs have black foreground, and kdenlive uses white foreground, but is a solution, and it works.