The screenshot below shows what`s happening with hair

I am not sure I understand the problem...As far as I have seen, textures -should- update the particle when tweaked. I just did a commit that avoids updating when the active texture is changed in the particle tab but I don't think changing the texture settings otherwise should not update.. Do I miss something here?

What I have seen however is that changing between textures in the particle tab strangely only updates half the sphere each time.

The problem here is that it updates itself when you click literally anything not necessarily involving texture.
And even if it should, the change shouldn`t be so dramatic, unpredictable, etc.

Look at the screenshots I`ve uploaded. The changes didn`t happen because I changed "density". I clicked some irrelevant checkbox somewhere. Also the density map covers almost the whole head where you can see there are totally bald areas, not to mention weird, changing amounts of feathers.

I can see the problem in the screenshot but it would help if the actual test file had a similar behaviour (which it doesn't, each "update" does the whole sphere). I can see how it would be nice for updates to only refresh the relevant areas though.

@Antonis Ryakiotakis (psy-fi) the problem is when influence=>density (texture) is ticked. Every time you click for example influence=>general=>time or some other texture/particle system settings like "hair lenght" (even without change the value) it exactly looks like particle system changes seeds value (seed is still "0", but hair change their location).

When influence=>density (texture) is unticked everything is ok.