Diagonal labels take too much space

[mourner]

Copied from #1641

I also noticed that diagonal lines are covered by one big rectangle, and that means that a lot of labels that could be drawn aren't because of false positives. In Kothic JS, we cover diagonal lines by a set of small offset rectangles, and I think you should try the same. Because of bulk insertion, it shouldn't affect performance much.

[jfirebaugh]

Can you give an example? I was having a hard time seeing this.

[mourner]

OK, here's how all line labels are currently put in RTree for collision detection:

And here's how we could improve that to make more room for other labels:

It may not be very noticeable on grid-like cities like Washington, but on cities with more chaotic street placement the effect will be more pronounced.

[mourner]

Here's a Kothic screenshot to illustrate how collisions are handled there (notice the non-grid like street pattern with lots of labels along curvy paths and how many labels fit on the map).

[bhousel]

whoa, I had a hunch about the area labels being off, but iD's collision boxes are worse than I realized:

[mourner]

Wow. If you decide to tackle this, you can reuse some rectangle covering code from GL JS.

[bhousel]

I did this today, looks pretty cool!