On 06/26/2016 10:47 AM, Mike Wey wrote:

Seems to be fixed in GTK+ 3.20. I'll look into creating a newer installer.

Binaries are up:
http://master.dl.sourceforge.net/project/gtkd-packages/gtk3-runtime/gtk3-runtime3.20.432-bit.exe
http://master.dl.sourceforge.net/project/gtkd-packages/gtk3-runtime/gtk3-runtime3.20.464-bit.exe

Speed wise adding the columns takes about twice the time as it does on
linux. its in the 80ms range for me.