refactor: separate elements logic into a standalone package (#9285)

packages/element/src/collision.ts

@@ -0,0 +1,319 @@
+import { isTransparent } from "@excalidraw/common";
+import {
+  curveIntersectLineSegment,
+  isPointWithinBounds,
+  line,
+  lineSegment,
+  lineSegmentIntersectionPoints,
+  pointFrom,
+  pointRotateRads,
+  pointsEqual,
+} from "@excalidraw/math";
+
+import {
+  ellipse,
+  ellipseLineIntersectionPoints,
+} from "@excalidraw/math/ellipse";
+
+import { isPointInShape, isPointOnShape } from "@excalidraw/utils/collision";
+import { getPolygonShape } from "@excalidraw/utils/shape";
+
+import type {
+  GlobalPoint,
+  LineSegment,
+  LocalPoint,
+  Polygon,
+  Radians,
+} from "@excalidraw/math";
+
+import type { GeometricShape } from "@excalidraw/utils/shape";
+
+import type { FrameNameBounds } from "@excalidraw/excalidraw/types";
+
+import { getBoundTextShape, isPathALoop } from "./shapes";
+import { getElementBounds } from "./bounds";
+import {
+  hasBoundTextElement,
+  isIframeLikeElement,
+  isImageElement,
+  isTextElement,
+} from "./typeChecks";
+import {
+  deconstructDiamondElement,
+  deconstructRectanguloidElement,
+} from "./utils";
+
+import type {
+  ElementsMap,
+  ExcalidrawDiamondElement,
+  ExcalidrawElement,
+  ExcalidrawEllipseElement,
+  ExcalidrawRectangleElement,
+  ExcalidrawRectanguloidElement,
+} from "./types";
+
+export const shouldTestInside = (element: ExcalidrawElement) => {
+  if (element.type === "arrow") {
+    return false;
+  }
+
+  const isDraggableFromInside =
+    !isTransparent(element.backgroundColor) ||
+    hasBoundTextElement(element) ||
+    isIframeLikeElement(element) ||
+    isTextElement(element);
+
+  if (element.type === "line") {
+    return isDraggableFromInside && isPathALoop(element.points);
+  }
+
+  if (element.type === "freedraw") {
+    return isDraggableFromInside && isPathALoop(element.points);
+  }
+
+  return isDraggableFromInside || isImageElement(element);
+};
+
+export type HitTestArgs<Point extends GlobalPoint | LocalPoint> = {
+  x: number;
+  y: number;
+  element: ExcalidrawElement;
+  shape: GeometricShape<Point>;
+  threshold?: number;
+  frameNameBound?: FrameNameBounds | null;
+};
+
+export const hitElementItself = <Point extends GlobalPoint | LocalPoint>({
+  x,
+  y,
+  element,
+  shape,
+  threshold = 10,
+  frameNameBound = null,
+}: HitTestArgs<Point>) => {
+  let hit = shouldTestInside(element)
+    ? // Since `inShape` tests STRICTLY againt the insides of a shape
+      // we would need `onShape` as well to include the "borders"
+      isPointInShape(pointFrom(x, y), shape) ||
+      isPointOnShape(pointFrom(x, y), shape, threshold)
+    : isPointOnShape(pointFrom(x, y), shape, threshold);
+
+  // hit test against a frame's name
+  if (!hit && frameNameBound) {
+    hit = isPointInShape(pointFrom(x, y), {
+      type: "polygon",
+      data: getPolygonShape(frameNameBound as ExcalidrawRectangleElement)
+        .data as Polygon<Point>,
+    });
+  }
+
+  return hit;
+};
+
+export const hitElementBoundingBox = (
+  x: number,
+  y: number,
+  element: ExcalidrawElement,
+  elementsMap: ElementsMap,
+  tolerance = 0,
+) => {
+  let [x1, y1, x2, y2] = getElementBounds(element, elementsMap);
+  x1 -= tolerance;
+  y1 -= tolerance;
+  x2 += tolerance;
+  y2 += tolerance;
+  return isPointWithinBounds(
+    pointFrom(x1, y1),
+    pointFrom(x, y),
+    pointFrom(x2, y2),
+  );
+};
+
+export const hitElementBoundingBoxOnly = <
+  Point extends GlobalPoint | LocalPoint,
+>(
+  hitArgs: HitTestArgs<Point>,
+  elementsMap: ElementsMap,
+) => {
+  return (
+    !hitElementItself(hitArgs) &&
+    // bound text is considered part of the element (even if it's outside the bounding box)
+    !hitElementBoundText(
+      hitArgs.x,
+      hitArgs.y,
+      getBoundTextShape(hitArgs.element, elementsMap),
+    ) &&
+    hitElementBoundingBox(hitArgs.x, hitArgs.y, hitArgs.element, elementsMap)
+  );
+};
+
+export const hitElementBoundText = <Point extends GlobalPoint | LocalPoint>(
+  x: number,
+  y: number,
+  textShape: GeometricShape<Point> | null,
+): boolean => {
+  return !!textShape && isPointInShape(pointFrom(x, y), textShape);
+};
+
+/**
+ * Intersect a line with an element for binding test
+ *
+ * @param element
+ * @param line
+ * @param offset
+ * @returns
+ */
+export const intersectElementWithLineSegment = (
+  element: ExcalidrawElement,
+  line: LineSegment<GlobalPoint>,
+  offset: number = 0,
+): GlobalPoint[] => {
+  switch (element.type) {
+    case "rectangle":
+    case "image":
+    case "text":
+    case "iframe":
+    case "embeddable":
+    case "frame":
+    case "magicframe":
+      return intersectRectanguloidWithLineSegment(element, line, offset);
+    case "diamond":
+      return intersectDiamondWithLineSegment(element, line, offset);
+    case "ellipse":
+      return intersectEllipseWithLineSegment(element, line, offset);
+    default:
+      throw new Error(`Unimplemented element type '${element.type}'`);
+  }
+};
+
+const intersectRectanguloidWithLineSegment = (
+  element: ExcalidrawRectanguloidElement,
+  l: LineSegment<GlobalPoint>,
+  offset: number = 0,
+): GlobalPoint[] => {
+  const center = pointFrom<GlobalPoint>(
+    element.x + element.width / 2,
+    element.y + element.height / 2,
+  );
+  // To emulate a rotated rectangle we rotate the point in the inverse angle
+  // instead. It's all the same distance-wise.
+  const rotatedA = pointRotateRads<GlobalPoint>(
+    l[0],
+    center,
+    -element.angle as Radians,
+  );
+  const rotatedB = pointRotateRads<GlobalPoint>(
+    l[1],
+    center,
+    -element.angle as Radians,
+  );
+
+  // Get the element's building components we can test against
+  const [sides, corners] = deconstructRectanguloidElement(element, offset);
+
+  return (
+    // Test intersection against the sides, keep only the valid
+    // intersection points and rotate them back to scene space
+    sides
+      .map((s) =>
+        lineSegmentIntersectionPoints(
+          lineSegment<GlobalPoint>(rotatedA, rotatedB),
+          s,
+        ),
+      )
+      .filter((x) => x != null)
+      .map((j) => pointRotateRads<GlobalPoint>(j!, center, element.angle))
+      // Test intersection against the corners which are cubic bezier curves,
+      // keep only the valid intersection points and rotate them back to scene
+      // space
+      .concat(
+        corners
+          .flatMap((t) =>
+            curveIntersectLineSegment(t, lineSegment(rotatedA, rotatedB)),
+          )
+          .filter((i) => i != null)
+          .map((j) => pointRotateRads(j, center, element.angle)),
+      )
+      // Remove duplicates
+      .filter(
+        (p, idx, points) => points.findIndex((d) => pointsEqual(p, d)) === idx,
+      )
+  );
+};
+
+/**
+ *
+ * @param element
+ * @param a
+ * @param b
+ * @returns
+ */
+const intersectDiamondWithLineSegment = (
+  element: ExcalidrawDiamondElement,
+  l: LineSegment<GlobalPoint>,
+  offset: number = 0,
+): GlobalPoint[] => {
+  const center = pointFrom<GlobalPoint>(
+    element.x + element.width / 2,
+    element.y + element.height / 2,
+  );
+
+  // Rotate the point to the inverse direction to simulate the rotated diamond
+  // points. It's all the same distance-wise.
+  const rotatedA = pointRotateRads(l[0], center, -element.angle as Radians);
+  const rotatedB = pointRotateRads(l[1], center, -element.angle as Radians);
+
+  const [sides, curves] = deconstructDiamondElement(element, offset);
+
+  return (
+    sides
+      .map((s) =>
+        lineSegmentIntersectionPoints(
+          lineSegment<GlobalPoint>(rotatedA, rotatedB),
+          s,
+        ),
+      )
+      .filter((p): p is GlobalPoint => p != null)
+      // Rotate back intersection points
+      .map((p) => pointRotateRads<GlobalPoint>(p!, center, element.angle))
+      .concat(
+        curves
+          .flatMap((p) =>
+            curveIntersectLineSegment(p, lineSegment(rotatedA, rotatedB)),
+          )
+          .filter((p) => p != null)
+          // Rotate back intersection points
+          .map((p) => pointRotateRads(p, center, element.angle)),
+      )
+      // Remove duplicates
+      .filter(
+        (p, idx, points) => points.findIndex((d) => pointsEqual(p, d)) === idx,
+      )
+  );
+};
+
+/**
+ *
+ * @param element
+ * @param a
+ * @param b
+ * @returns
+ */
+const intersectEllipseWithLineSegment = (
+  element: ExcalidrawEllipseElement,
+  l: LineSegment<GlobalPoint>,
+  offset: number = 0,
+): GlobalPoint[] => {
+  const center = pointFrom<GlobalPoint>(
+    element.x + element.width / 2,
+    element.y + element.height / 2,
+  );
+
+  const rotatedA = pointRotateRads(l[0], center, -element.angle as Radians);
+  const rotatedB = pointRotateRads(l[1], center, -element.angle as Radians);
+
+  return ellipseLineIntersectionPoints(
+    ellipse(center, element.width / 2 + offset, element.height / 2 + offset),
+    line(rotatedA, rotatedB),
+  ).map((p) => pointRotateRads(p, center, element.angle));
+};