I have finished uploading binary packages for MATE 1.12 built against GTK+3 for Slackware-Current in the usual location, a repository provided by Darren Austin under testing/ directory. I wanted to give a preview of what's coming for MATE 1.12 in Slackware-Current since it will be built against GTK+3 instead of GTK+2.
Upstream developers are now preparing to take major changes for next release of MATE so that it's built against GTK+3 only since there are some bugs that can only be fixed when all codes are GTK+3 compatible only.
Please help by testing it on a -current machine, preferrably a clean installation in virtual machine so that it reflects the current state of slackware-current development. Every packages were built against update per 6 November 2015.
For those upgrading from MATE 1.10 running -current, here are some changes compared with GTK+2 version:
New Packages in MATE 1.12:
Packages removed in MATE 1.12:
gtksourceview (replaced by gtksourceview3)
libunique (replaced by libunique3)
pygobject3 (Added to Slackware)
gtkmm (replaced by gtkmm3)
gnome-main-menu (not compatible with GTK+3)
For those wishing to build on their own machines, please use GTK3 branch from GitHub for now.