Number of particles per unit area?

Are there particles/hairs per unit area in particle setting? I would be convenient to control density when the object scale was change.

Thank you.

This is not possible ? Or am I missing something? I think this is very important functionallity to have. May I request somebody to code this? Help is very appreciated and thank you.

As far as I know, you can’t control density in terms of particles/area, just in terms of total particles.
You can, however, control density setting weights on a verte group, then assigning it on Particles>Vertex Groups>Density

I wish this features will shortly be implemented, is it difficult? I don’t know, I’m not a programmer.

You mean like this?

No, I did not mean that, that is just weight paint. I mean particles/area.