66 lines
1.6 KiB
TypeScript
66 lines
1.6 KiB
TypeScript
import { Bounds } from "./excalidraw/element/bounds";
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import { Point } from "./excalidraw/types";
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export type LineSegment = [Point, Point];
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export function getBBox(line: LineSegment): Bounds {
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return [
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Math.min(line[0][0], line[1][0]),
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Math.min(line[0][1], line[1][1]),
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Math.max(line[0][0], line[1][0]),
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Math.max(line[0][1], line[1][1]),
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];
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}
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export function crossProduct(a: Point, b: Point) {
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return a[0] * b[1] - b[0] * a[1];
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}
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export function doBBoxesIntersect(a: Bounds, b: Bounds) {
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return a[0] <= b[2] && a[2] >= b[0] && a[1] <= b[3] && a[3] >= b[1];
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}
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export function translate(a: Point, b: Point): Point {
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return [a[0] - b[0], a[1] - b[1]];
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}
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const EPSILON = 0.000001;
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export function isPointOnLine(l: LineSegment, p: Point) {
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const p1 = translate(l[1], l[0]);
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const p2 = translate(p, l[0]);
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const r = crossProduct(p1, p2);
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return Math.abs(r) < EPSILON;
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}
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export function isPointRightOfLine(l: LineSegment, p: Point) {
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const p1 = translate(l[1], l[0]);
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const p2 = translate(p, l[0]);
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return crossProduct(p1, p2) < 0;
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}
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export function isLineSegmentTouchingOrCrossingLine(
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a: LineSegment,
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b: LineSegment,
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) {
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return (
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isPointOnLine(a, b[0]) ||
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isPointOnLine(a, b[1]) ||
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(isPointRightOfLine(a, b[0])
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? !isPointRightOfLine(a, b[1])
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: isPointRightOfLine(a, b[1]))
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);
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}
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// https://martin-thoma.com/how-to-check-if-two-line-segments-intersect/
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export function doLineSegmentsIntersect(a: LineSegment, b: LineSegment) {
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return (
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doBBoxesIntersect(getBBox(a), getBBox(b)) &&
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isLineSegmentTouchingOrCrossingLine(a, b) &&
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isLineSegmentTouchingOrCrossingLine(b, a)
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);
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}
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