A plan for the formation of the GTK 4 release has been outlined. It is noted that it will take about another year to bring GTK 4 to its proper form (GTK 4 has been developing since summer 2016). Until the end of 2019, it is planned to prepare another experimental release of the GTK 3.9x series, then in the spring of 2020 the final test release of GTK 3.99 will be offered, which includes all the intended functionality. The release of GTK 4 is expected in early fall 2020, simultaneously with GNOME 3.38.
Before the final release, it is necessary to bring to the end five planned functional changes, including the work of replacing fixed widgets with scalable views, a new API for animating and translating effects and indicators of progress on it, completing the processing of the pop-up menu system (developing ideas related to nested submenus and drop-down menus), replacing the old hotkey system with event handlers, finalizing the new API for Drag & Drop operations.
Among the optional features that team would like to add before the release of GTK 4, the "UI designer" widget, improved means for splitting the upper panels and the widget repository through which experimental widgets can be delivered without integration into the main structure of GTK stand out. The development of tools for porting applications to GTK4 is also mentioned, for example, the preparation of the corresponding versions of the GtkSourceView, vte and webkitgtk libraries, as well as the provision of platform support. For example, the OpenGL-based rendering system works well on Linux, but the Vulkan-based rendering system still needs to be improved. On Windows, the Cairo library is used for rendering, but an alternative implementation based on ANGLE (a layer for translating OpenGL ES calls to OpenGL, Direct3D 9/11, Desktop GL and Vulkan) is under development. For macOS, a fully functional rendering backend is not yet available.