I would reuse the Renderer, but other than that i don't see anything wrong.

thanks mike. unfortunately it does not make a difference. even w/o a
renderer at all, just adding empty columns, TreeView still needs 16s to
append 512 columns. this is 32 columns/sec. it takes longer to append a
column than for an ego shooter to render a full HD scene...

i also played with fixed sizes (width, height) to now avail. frustrating
this is.