Turns out just 24 hours after i posted about MATE 1.18 preparations, upstream developers have finally announced the final version of MATE 1.18. This release has reached an interesting milestone, which is to migrate all MATE components to GTK+3, leaving GTK+2 code base which is no longer updated and have many limitations. Along with this transition, many deprecated components are also being migrated to the new technologies.
Upstream developers have generously supported GTK+3-3.14.x, which is still used by RHEL and Slackware 14.2 as their minimum supported version of GTK+3. They do support all newer GTK+3, up to GTK+3-3.22.x. Since GTK+4 is still far away and it will be co-installable with previous GTK+3, upstream developers will have more time to fix many things with GTK+3 before starts struggling with new GTK+4 in the future.
MATE 1.18 have also started to provide support for libinput for mouse and touchpad. Since -current has included libinput, it will have better support on handling inputs in the next release. It has also replaced deprecated upower suspend/hibernate functions with ConsoleKit2
equivalents that is supported in Slackware and Gentoo. There are also reworked font-viewer in mate-control-center, lots of new filetype support in engrampa, and porting of Pluma and eom plugins to libpeas.
The biggest change goes to caja, the file manager. It is ported from libunique to GtkApplication, added copy queue and pausing feature, delete confirmation, directory navigation buttons, better notification with removeable drives, and many more.
Please note that there are still some theme-related and mate-panel glitches with GTK+3 and it's a known issues for some time. The developers are working on it day by day.
All the SlackBuilds source code has been pushed to github and gitlab. Website has been updated with MATE 1.18 screenshots, and binary packages have been uploaded to Slackware.uk for both Stable and Current (x86_64 only) release. It will be included in the next Slackware Live ISO by AlienBOB as well.
Enjoy MATE 1.18!!!