Improve the snapping system

[Keavon]

The current approach is very MVP.

[mbfraga]

I've been working on this in my own app, and my basic algorithm involves the following:

1. Collect candidate geometries and generate vertical and horizontal snap points (how you generate snap points is a bit specific to UX decisions),
2. Filter candidates based on rough area filters
3. Then you generate snap points from the thing you want to snap to, and you do a comparison--looking for fuzzy and exact matches.
4. If there is an exact you don't need to snap--if there is a fuzzy you snap!

Snapping to geometries or individual points becomes a detail at that point.

This algo (in c++) is a bit brute-forcy, but it scales quite easily to tens of thousands, as long as rendering can keep up...blend2d can keep up quite nicely. At hundreds of thousands is somewhat usable but a bit slow--but then again...snapping at hundrerds of thousands is pointless.

Here is a gif (low fps haha) where you can see the behavior. When I add the debug ellipses, those are 10k items each time. With those 20k items, there is zero perceptive performance loss.

Once I open my code I'll post it here as well.

[Keavon]

Keavon — 02/13/2022
@0HyperCube how difficult would it be to display the point that is being snapped to?
i.e. if you have something (like a gradient or another anchor point) snapping to an anchor point, rendering the anchor point's square to show what is causing there to be a line across the screen

0hypercube — 02/13/2022
Only for shape points?

Keavon — 02/13/2022
Are there things other than shape points which are the source of snapping candidates?

0hypercube — 02/13/2022
layer bounds and centres

Keavon — 02/13/2022
Ideally in that case, we'd draw the entire shape's outline
So the specific anchor point when snapping to an anchor point, and the entire shape outline when snapping to the bounding box edge/center.

0hypercube — 02/13/2022
Probably reasonably easy, but I'm quite busy for the next few days

Keavon — 02/13/2022
Ok, good to hear it's easy. No worries about getting it done immediately, but I was wondering how much work it would be. I'll put it near on the priority list if you're interested in taking that on next time you have some free time and an interest.
More more little improvement would be making the anchor points snap to other anchor points
https://files.keavon.com/-/LimeComfortableLimpkin/capture_2_.mp4
I'll file issues for both of those

0hypercube — 02/13/2022
All snapping should snap to all path control points in the document?

Keavon — 02/13/2022
I think generally: points to points, bounds to bounds
So dragging around an anchor point should snap to the other anchor points (plus also bounds)
But drawing a new rectangle, or resizing the cage for an existing shape, should only snap to other bounding boxes

0hypercube — 02/13/2022
Should snapping bounds to bounds display a shape outline?

Keavon — 02/13/2022
Yes

[0HyperCube]

@Keavon Do we also want to show the points on the faint lines?

[Keavon]

@0HyperCube what points?