curve tool controls fail about delaboratory HOT 3 CLOSED

Well there are three different issues here.

Combined curve for "all channels" were already proposed by some people. The 
main problem with combined curve is that it is usable only for RGB colorspace, 
and the main idea of delaboratory is to work in multiple colorspaces. It could 
be also partially usable with CMY channels in CMYK and AB channels in LAB, but 
that's all. If you think separate layer for combined curve is needed please 
open feature request in new issue and we can discuss it there.

Control points from 0.0 and 1.0 are fixed in their X positions, because each 
curve must start at 0 and end at 1.0. If I move point from this place I will 
need to add new one, so my choice was to disallow moving it.

The problem with point control after releasing mouse button is a real bug and 
it need to be fixed. I tried to put some code to help (it will be available in 
next beta), but if problem still happens please try to find out how to 
reproduce it, when it happens - because on Linux I am not able to achieve that.

Please describe when it happens.

Does it happen always when you open curve editor or sometimes?

Here I read that you need to pick 0,0 or 255, 255 first.
In issue 40 I read "When curves dialog is opened, simply moving mouse cursor 
over the curve seems to use one of the points".

Well that's not the same.

no update for half year