2021-10-12 15:07:00 +04:00

69 lines
2.5 KiB
Swift

//
// PathElement.swift
// lottie-swift
//
// Created by Brandon Withrow on 1/11/19.
//
import Foundation
import CoreGraphics
/**
A path section, containing one point and its length to the previous point.
The relationship between this path element and the previous is implicit.
Ideally a path section would be defined by two vertices and a length.
We don't do this however, as it would effectively double the memory footprint
of path data.
*/
struct PathElement {
/// The absolute Length of the path element.
let length: CGFloat
/// The vertex of the element
let vertex: CurveVertex
/// Returns a new path element define the span from the receiver to the new vertex.
func pathElementTo(_ toVertex: CurveVertex) -> PathElement {
return PathElement(length: vertex.distanceTo(toVertex), vertex: toVertex)
}
/// Initializes a new path with length of 0
init(vertex: CurveVertex) {
self.length = 0
self.vertex = vertex
}
/// Initializes a new path with length
fileprivate init(length: CGFloat, vertex: CurveVertex) {
self.length = length
self.vertex = vertex
}
func updateVertex(newVertex: CurveVertex) -> PathElement {
return PathElement(length: length, vertex: newVertex)
}
/// Splits an element span defined by the receiver and fromElement to a position 0-1
func splitElementAtPosition(fromElement: PathElement, atLength: CGFloat) ->
(leftSpan: (start: PathElement, end: PathElement), rightSpan: (start: PathElement, end: PathElement)) {
/// Trim the span. Start and trim go into the first, trim and end go into second.
let trimResults = fromElement.vertex.trimCurve(toVertex: vertex, atLength: atLength, curveLength: length, maxSamples: 3)
/// Create the elements for the break
let spanAStart = PathElement(length: fromElement.length,
vertex: CurveVertex(point: fromElement.vertex.point,
inTangent: fromElement.vertex.inTangent,
outTangent: trimResults.start.outTangent))
/// Recalculating the length here is a waste as the trimCurve function also accurately calculates this length.
let spanAEnd = spanAStart.pathElementTo(trimResults.trimPoint)
let spanBStart = PathElement(vertex: trimResults.trimPoint)
let spanBEnd = spanBStart.pathElementTo(trimResults.end)
return (leftSpan: (start: spanAStart, end: spanAEnd),
rightSpan: (start: spanBStart, end: spanBEnd))
}
}