When viewing a curve with a lot of keys totally zoomed out,
the keys might be closer to each other than a pixel.
The code would still draw a line between them,
costing time in the draw code.
This PR skips any keys that are too close to each other in screen space.
## Performance
The setup: 62 bones with 6000f of animation keyed on every frame.
No keys displayed, just the curves.
| - | before | after |
| - | - | - |
| zoomed in | 11μs | 17μs |
| zoomed out | 55μs | 30μs |
So a small performance penalty when zoomed in in exchange for a big gain when zoomed out.
There is a small change in visuals when zoomed out a lot.
Because this change averages keys that are too close together,
it results in a small loss of high frequency detail.
## The logic
If `prevbezt` and `bezt` are too close it will not draw,
but extend a bounding box with `prevbezt` and `bezt` including handles if needed.
Eventually the keys will be far enough apart to draw.
At this point, draw the center of the bounding box and reset it.
Now because there could be the case where `bezt` in the
current loop is super far out (e.g 5 keys with 1f spacing and the 6th key is at f1000)
we need to recalculate the bounding box again.
In case the keys are far away, just draw normally.
If it is close still, the same process repeats.
Pull Request: https://projects.blender.org/blender/blender/pulls/110788
d7e3961a82