clearClip is almost 4 more times expensive then setClip

You really only want to only use setClip in onPartialUpdate.  There is no need for it in onUpdate.

1. bug is bug

2. yes I can and even I do it and even I have to do it but use setClip(device_size) instead of clearlip() - first usage setClip practically force tu use somewhen clearClip

3. if you see my WF you surly will know that it isn't only one drawing but drawing in loop - it's not enough to clearClip only once - practically I have to clearclip after each of controls because I don't know if next control call setClip or not (there are some IF's).

You can set multiple clip regions, update each one, and the only do the clear clip later.

I didn't  know that clearClip do nothing except setClip(device_size) so thought setClip has to call cleraClip first to do do some work so it means setClip has to be more expensive.

That is surprising since clearClip calls setClip internally and does nothing else. Internally, setClip does some additional work if the dc is not a buffered bitmap.

When using a buffered bitmap, I see dc.setClip is about half the cost of dc.clearClip. This makes sense to me as dc.setClip is native and just sets a few variables so the cost is very small. The call to dc.clearClip is that plus stack management time (pushing 4 values on the stack and popping them from the stack). I could be wrong here, but it does seem to make sense to me.

That said, I don't understand what you mean by this...

setClip should contain clearClip becouse there is no multiply clips