The GTK 4.0 cross-platform UI Element Library will not be released this year and is not expected in the spring of next year. It is expected that the novelty will be released in the fall of 2020. At the moment, the project still has a number of problems that need to be addressed. Therefore, it is assumed that before the end of 2019 they will release an early version of 3.99, which will get to the release by spring.
It is reported that during the annual GNAD GUADEC conference there was a lot of discussion on the topic of GTK 4.0. As a result, some results have been achieved. In particular, the "four" will add additional metadata for index files, which will improve the "dark mode". Also in GTK4 is a scalable list widget that will replace row widgets.
Animation changes are also promised. Animated elements will reportedly work similarly to CSS in GTK4. Of the little things, we note the refinement of the menu, the use of event controllers for shortcuts, the improvement of the drag and drop API, as well as a number of optimizations for widgets.
That being said, the Vulkan rendering system for GTK 4.0 still needs some fixes. Thus, the time has not yet come to “freeze” the code base.
Note that GTK+ 3.0.0 was released on February 10, 2011. This library, along with Qt, is one of the two most popular solutions today for building a graphical interface for applications in the X Window System.
Source: 3dnews.ru