feat: Elbow arrow segment fixing & positioning (#8952)

Co-authored-by: dwelle <5153846+dwelle@users.noreply.github.com>
Co-authored-by: David Luzar <5153846+dwelle@users.noreply.github.com>

packages/math/line.ts

@@ -1,4 +1,4 @@
-import { pointCenter, pointRotateRads } from "./point";
+import { pointCenter, pointFrom, pointRotateRads } from "./point";
 import type { GlobalPoint, Line, LocalPoint, Radians } from "./types";
 
 /**
@@ -38,8 +38,16 @@ export function lineFromPointArray<P extends GlobalPoint | LocalPoint>(
     : undefined;
 }
 
-// return the coordinates resulting from rotating the given line about an origin by an angle in degrees
-// note that when the origin is not given, the midpoint of the given line is used as the origin
+/**
+ * Return the coordinates resulting from rotating the given line about an
+ * origin by an angle in degrees note that when the origin is not given,
+ * the midpoint of the given line is used as the origin
+ *
+ * @param l
+ * @param angle
+ * @param origin
+ * @returns
+ */
 export const lineRotate = <Point extends LocalPoint | GlobalPoint>(
   l: Line<Point>,
   angle: Radians,
@@ -50,3 +58,29 @@ export const lineRotate = <Point extends LocalPoint | GlobalPoint>(
     pointRotateRads(l[1], origin || pointCenter(l[0], l[1]), angle),
   );
 };
+
+/**
+ * Determines the intersection point (unless the lines are parallel) of two
+ * lines
+ *
+ * @param a
+ * @param b
+ * @returns
+ */
+export const linesIntersectAt = <Point extends GlobalPoint | LocalPoint>(
+  a: Line<Point>,
+  b: Line<Point>,
+): Point | null => {
+  const A1 = a[1][1] - a[0][1];
+  const B1 = a[0][0] - a[1][0];
+  const A2 = b[1][1] - b[0][1];
+  const B2 = b[0][0] - b[1][0];
+  const D = A1 * B2 - A2 * B1;
+  if (D !== 0) {
+    const C1 = A1 * a[0][0] + B1 * a[0][1];
+    const C2 = A2 * b[0][0] + B2 * b[0][1];
+    return pointFrom<Point>((C1 * B2 - C2 * B1) / D, (A1 * C2 - A2 * C1) / D);
+  }
+
+  return null;
+};

packages/math/point.ts

@@ -61,6 +61,22 @@ export function pointFromVector<P extends GlobalPoint | LocalPoint>(
   return v as unknown as P;
 }
 
+/**
+ * Convert the coordiante object to a point.
+ *
+ * @param coords The coordinate object with x and y properties
+ * @returns
+ */
+export function pointFromCoords<Point extends GlobalPoint | LocalPoint>({
+  x,
+  y,
+}: {
+  x: number;
+  y: number;
+}) {
+  return [x, y] as Point;
+}
+
 /**
  * Checks if the provided value has the shape of a Point.
  *
@@ -217,7 +233,10 @@ export function pointDistanceSq<P extends LocalPoint | GlobalPoint>(
   a: P,
   b: P,
 ): number {
-  return Math.hypot(b[0] - a[0], b[1] - a[1]);
+  const xDiff = b[0] - a[0];
+  const yDiff = b[1] - a[1];
+
+  return xDiff * xDiff + yDiff * yDiff;
 }
 
 /**