GTK4 Ejects The Mir Backend & Drops The Big GDK Lock

After adding the Mir back-end for the GTK+ 3.16 cycle, GTK+ 4.0 is dropping this back-end for the Canonical-developed display server.

The Mir back-end has been removed from the latest GTK+ code. This clears out about 6,500 lines of code from the tool-kit's codebase. The removal of the Mir back-end is coming since Mir has been focusing on Wayland protocol support to which GTK+ has more mature Wayland support than Mir. Since Mir's change of focus last year and the work the past number of months, the Wayland support on Mir has become more viable.

Canonical developers have previously communicated they are fine with toolkits and other programs removing their Mir back-ends in favor of existing Wayland support where that Wayland code works fine on Mir.

Another big change this weekend in GTK+ is dropping the big GDK lock. The background of the removal of this big lock can be found via this bug report.

These latest GTK changes come following the GTK+ hackfest in Brussels that happened prior to this past weekend's FOSDEM event. The developers reiterated their plans at the hackfest for aiming to release GTK+ 4.0 this fall.