Geometry, interaction, UI, and typing extensions for Snap.svg (Bezier/PolyBezier, polygons, hulls, BBox, Element/Paper helpers)

[vakarelov]

Summary

This PR adds a comprehensive set of geometry utilities, interaction primitives, UI-building helpers, and TypeScript types on top of Snap.svg. It retains compatibility with the core API while enabling advanced tasks such as Bezier editing, polygon/hull analysis, draggable and constrained movement, border image tiling, HTML embedding via foreignObject, rasterization, and more.

Motivation

• Provide modern vector-geometry primitives within Snap.svg, minimizing external dependencies during prototyping and production.
• Improve developer ergonomics with high-level Element/Paper helpers for transforms, interactions, and composition.
• Offer reliable types for better IDE support and safer code.

Scope of Changes

New/extended modules (src/)

• bezier.js: Full Bezier and PolyBezier engine (split, length, normals, offset/outline, intersections, arcs, PolyBezier aggregation).
• polygons.js: Polygon operations (intersection, point-in-polygon, area, distance/alignment helpers).
• convex_overlap.js: SAT-based convex polygon overlap checks; exposed under Snap.polygons.sat.
• hull.js: Concave hull integration (hull.js) plus convex hull wrapper.
• bbox.js: BBox class and Snap.box helpers with rich geometry API and rotating bbox.
• element_extensions.js: Element prototype enhancements (IDs/refs, coordinate transforms, overlaps, center of mass/rotation, path conversion, clip/mask, interaction: move/revolve/draggable, transforms and utilities).
• paper_extensions.js: Paper prototype enhancements (grid/zigzag/arcFan/disk segments/circle/ellipse builders; foreignObject/htmlInsert; embeddedSVG; canvas; button; text helpers; border image tiling; extension processor; Snap.FORCE_AFTER).
• paper_extensions.js: Paper prototype enhancements (grid/zigzag/arcFan/disk segments/circle/ellipse builders; foreignObject/htmlInsert; embeddedSVG; canvas; button; text helpers; border image tiling; extension processor; Snap.FORCE_AFTER); plus Paper constructors/methods copied onto Element to enable method chaining during SVG construction.
• gui_interactions.js: GUI helpers: cursors, region select, event wiring conveniences, overlay/canvas rasterization.
• colors.js: Material UI and Flat UI palettes; Snap.importMUIColors; Snap.getIndexColor.
• jsdoc-types.js: Central typedefs for points, ranges, bbox-like, polar, etc.

Types

• types/snap.svg.d.ts: Ambient declarations for the above APIs plus core Snap types (Paper, Element, Mina, path helpers, etc.).

Demos/docs

• Existing demos remain available in demos/; new features are exercised via code snippets in doc/WHATS_NEW.md.

Breaking Changes

• None intentionally. Additions are primarily additive to Element.prototype, Paper.prototype, and Snap.
• Note: Element.remove() is enhanced to also clean linked clipPaths/masks/refs. This is stricter behavior but should be non-breaking for typical workflows.

Performance Considerations

• Geometry operations (Bezier outline/offset, polygon intersection, hull) are computational; avoid running them per-frame on large datasets.
• Border image auto-update uses mutation observers; impact should be negligible for typical attribute changes, but avoid excessive mutation churn.
• BBox computations use a cached convex hull (CHull) to keep rotated bbox and overlap queries fast even after transforms.

Migration and Usage Notes

• Prefer helpers:
  • el.globalToLocal(p), el.getCursorPoint(evt) for coordinate math.
  • el.makeDraggable({ bounds, snap, onstart, onmove, onend }) for drag.
  • paper.htmlInsert() for HTML overlays via foreignObject.
  • Snap.hull(points, concavity) and Snap.polygons.intersect(a, b) for polygon tasks.
  • Snap.box(...)/new Snap.BBox(...) for bbox operations.
  • Paper methods on Element enable method-chaining construction, e.g., el.rect(...).circle(...).path(...) (appended with Snap.FORCE_AFTER).
• If you previously cleaned clip/mask links manually on removal, this is now automatic.

Testing

• No new automated tests added in this PR. Existing test suite remains available in test/.
• Manual verification performed via demos and targeted usage of new helpers.
• Follow-ups: add focused unit tests for BBox math, SAT overlap, and Bezier outline reduce cases.

Documentation

• New document: doc/WHATS_NEW.md (highlights, APIs, examples, migration).
• Types: types/snap.svg.d.ts aligns with runtime surface.

Checklist

• New APIs documented (doc/WHATS_NEW.md)
• Type definitions updated (types/)
• Demos verified where applicable
• Unit tests for new math-heavy paths (planned follow-up)

[ibrierley]

Thanks for the work on this. I'm a bit out of touch on this now, and not sure if Dmitry checks this now, so feel a bit unconfident to handle. I had been previously pondering whether a Snap-CE (community edition) or something could be a way (but then there's issues with the site and versioning issues...). Is anyone else currently using Snap here and can do some verification and testing atm ?

[vakarelov]

Added additional powerful functionality related to non-linear transformations and element animations. See demo: demos
https://htmlpreview.github.io/?https://github.com/vakarelov/Snap.svg/master/demos/non-linear/index.html
Many more easing functions in mina.js, including a new easing construction engine. See demo: Snap.svg/demos
https://htmlpreview.github.io/?https://github.com/vakarelov/Snap.svg/master/demos/easings/index.html

Point-utils demos:
https://htmlpreview.github.io/?https://github.com/vakarelov/Snap.svg/master/demos/point-utils/voronoi/index.html
https://htmlpreview.github.io/?https://github.com/vakarelov/Snap.svg/master/demos/point-utils/proximity/index.html

Next: Full SVG-based 3D engine for Snap.svg

Demo for 3D Bezier projections:
https://htmlpreview.github.io/?https://github.com/vakarelov/Snap.svg/master//demos/bezier/bezier_projection_demo.html