Ok, now as being someone right in the middle of implementing yet another ide/editor, I gotta ask, how's such a feature useful to you at all? What would it provide? Except just looking cool at a glance.
I tend to rely on my spatial reasoning a lot, even when programming -- as I suspect many other programmers do.
When working on large project files, I find that I have to spend a lot of time scrolling up and down trying to find a particular function, especially if a project file contains lots of similar-looking wrapper functions. OTOH, in my brain, I know exactly where, spatially, the function resides relative to the document. I just have to find it.
So for me, the mini-map is a huge win, on the level of, "oh wow, how have I been programming all this time without it?"
And I loathe pop-up and drop-down menus with all of my function names. They only resolve one tiny aspect of my hunting; I don't have to scroll, but I still have to find the function I'm looking for.
With mini-map, I should be able to zero in on any part of the code that I'm looking for with a single click. I really want that.
