excalidraw/src/element/resizeElements.ts

import { SHIFT_LOCKING_ANGLE } from "../constants";
import { rescalePoints } from "../points";

import {
  rotate,
  adjustXYWithRotation,
  centerPoint,
  rotatePoint,
} from "../math";
import {
  ExcalidrawLinearElement,
  ExcalidrawTextElement,
  NonDeletedExcalidrawElement,
  NonDeleted,
  ExcalidrawElement,
  ExcalidrawTextElementWithContainer,
} from "./types";
import {
  getElementAbsoluteCoords,
  getCommonBounds,
  getResizedElementAbsoluteCoords,
  getCommonBoundingBox,
} from "./bounds";
import {
  isArrowElement,
  isBoundToContainer,
  isFreeDrawElement,
  isLinearElement,
  isTextElement,
} from "./typeChecks";
import { mutateElement } from "./mutateElement";
import { getFontString } from "../utils";
import { updateBoundElements } from "./binding";
import {
  TransformHandleType,
  MaybeTransformHandleType,
  TransformHandleDirection,
} from "./transformHandles";
import { Point, PointerDownState } from "../types";
import Scene from "../scene/Scene";
import {
  getApproxMinLineHeight,
  getApproxMinLineWidth,
  getBoundTextElement,
  getBoundTextElementId,
  getContainerElement,
  handleBindTextResize,
  getMaxContainerWidth,
} from "./textElement";

export const normalizeAngle = (angle: number): number => {
  if (angle >= 2 * Math.PI) {
    return angle - 2 * Math.PI;
  }
  return angle;
};

// Returns true when transform (resizing/rotation) happened
export const transformElements = (
  pointerDownState: PointerDownState,
  transformHandleType: MaybeTransformHandleType,
  selectedElements: readonly NonDeletedExcalidrawElement[],
  resizeArrowDirection: "origin" | "end",
  shouldRotateWithDiscreteAngle: boolean,
  shouldResizeFromCenter: boolean,
  shouldMaintainAspectRatio: boolean,
  pointerX: number,
  pointerY: number,
  centerX: number,
  centerY: number,
) => {
  if (selectedElements.length === 1) {
    const [element] = selectedElements;
    if (transformHandleType === "rotation") {
      rotateSingleElement(
        element,
        pointerX,
        pointerY,
        shouldRotateWithDiscreteAngle,
        pointerDownState.originalElements,
      );
      updateBoundElements(element);
    } else if (
      isTextElement(element) &&
      (transformHandleType === "nw" ||
        transformHandleType === "ne" ||
        transformHandleType === "sw" ||
        transformHandleType === "se")
    ) {
      resizeSingleTextElement(
        element,
        transformHandleType,
        shouldResizeFromCenter,
        pointerX,
        pointerY,
      );
      updateBoundElements(element);
    } else if (transformHandleType) {
      resizeSingleElement(
        pointerDownState.originalElements,
        shouldMaintainAspectRatio,
        element,
        transformHandleType,
        shouldResizeFromCenter,
        pointerX,
        pointerY,
      );
    }

    return true;
  } else if (selectedElements.length > 1) {
    if (transformHandleType === "rotation") {
      rotateMultipleElements(
        pointerDownState,
        selectedElements,
        pointerX,
        pointerY,
        shouldRotateWithDiscreteAngle,
        centerX,
        centerY,
      );
      return true;
    } else if (
      transformHandleType === "nw" ||
      transformHandleType === "ne" ||
      transformHandleType === "sw" ||
      transformHandleType === "se"
    ) {
      resizeMultipleElements(
        pointerDownState,
        selectedElements,
        transformHandleType,
        shouldResizeFromCenter,
        pointerX,
        pointerY,
      );
      return true;
    }
  }
  return false;
};

const rotateSingleElement = (
  element: NonDeletedExcalidrawElement,
  pointerX: number,
  pointerY: number,
  shouldRotateWithDiscreteAngle: boolean,
  originalElements: Map<string, NonDeleted<ExcalidrawElement>>,
) => {
  const [x1, y1, x2, y2] = getElementAbsoluteCoords(element);
  const cx = (x1 + x2) / 2;
  const cy = (y1 + y2) / 2;
  let angle = (5 * Math.PI) / 2 + Math.atan2(pointerY - cy, pointerX - cx);
  if (shouldRotateWithDiscreteAngle) {
    angle += SHIFT_LOCKING_ANGLE / 2;
    angle -= angle % SHIFT_LOCKING_ANGLE;
  }
  angle = normalizeAngle(angle);
  const boundTextElementId = getBoundTextElementId(element);

  mutateElement(element, { angle });
  if (boundTextElementId) {
    const textElement =
      Scene.getScene(element)?.getElement<ExcalidrawTextElementWithContainer>(
        boundTextElementId,
      );

    if (textElement && !isArrowElement(element)) {
      mutateElement(textElement, { angle });
    }
  }
};

const rescalePointsInElement = (
  element: NonDeletedExcalidrawElement,
  width: number,
  height: number,
  normalizePoints: boolean,
) =>
  isLinearElement(element) || isFreeDrawElement(element)
    ? {
        points: rescalePoints(
          0,
          width,
          rescalePoints(1, height, element.points, normalizePoints),
          normalizePoints,
        ),
      }
    : {};

const MIN_FONT_SIZE = 1;

const measureFontSizeFromWidth = (
  element: NonDeleted<ExcalidrawTextElement>,
  nextWidth: number,
): number | null => {
  // We only use width to scale font on resize
  let width = element.width;

  const hasContainer = isBoundToContainer(element);
  if (hasContainer) {
    const container = getContainerElement(element);
    if (container) {
      width = getMaxContainerWidth(container);
    }
  }
  const nextFontSize = element.fontSize * (nextWidth / width);
  if (nextFontSize < MIN_FONT_SIZE) {
    return null;
  }

  return nextFontSize;
};

const getSidesForTransformHandle = (
  transformHandleType: TransformHandleType,
  shouldResizeFromCenter: boolean,
) => {
  return {
    n:
      /^(n|ne|nw)$/.test(transformHandleType) ||
      (shouldResizeFromCenter && /^(s|se|sw)$/.test(transformHandleType)),
    s:
      /^(s|se|sw)$/.test(transformHandleType) ||
      (shouldResizeFromCenter && /^(n|ne|nw)$/.test(transformHandleType)),
    w:
      /^(w|nw|sw)$/.test(transformHandleType) ||
      (shouldResizeFromCenter && /^(e|ne|se)$/.test(transformHandleType)),
    e:
      /^(e|ne|se)$/.test(transformHandleType) ||
      (shouldResizeFromCenter && /^(w|nw|sw)$/.test(transformHandleType)),
  };
};

const resizeSingleTextElement = (
  element: NonDeleted<ExcalidrawTextElement>,
  transformHandleType: "nw" | "ne" | "sw" | "se",
  shouldResizeFromCenter: boolean,
  pointerX: number,
  pointerY: number,
) => {
  const [x1, y1, x2, y2] = getElementAbsoluteCoords(element);
  const cx = (x1 + x2) / 2;
  const cy = (y1 + y2) / 2;
  // rotation pointer with reverse angle
  const [rotatedX, rotatedY] = rotate(
    pointerX,
    pointerY,
    cx,
    cy,
    -element.angle,
  );
  let scale: number;
  switch (transformHandleType) {
    case "se":
      scale = Math.max(
        (rotatedX - x1) / (x2 - x1),
        (rotatedY - y1) / (y2 - y1),
      );
      break;
    case "nw":
      scale = Math.max(
        (x2 - rotatedX) / (x2 - x1),
        (y2 - rotatedY) / (y2 - y1),
      );
      break;
    case "ne":
      scale = Math.max(
        (rotatedX - x1) / (x2 - x1),
        (y2 - rotatedY) / (y2 - y1),
      );
      break;
    case "sw":
      scale = Math.max(
        (x2 - rotatedX) / (x2 - x1),
        (rotatedY - y1) / (y2 - y1),
      );
      break;
  }
  if (scale > 0) {
    const nextWidth = element.width * scale;
    const nextHeight = element.height * scale;
    const nextFontSize = measureFontSizeFromWidth(element, nextWidth);
    if (nextFontSize === null) {
      return;
    }
    const [nextX1, nextY1, nextX2, nextY2] = getResizedElementAbsoluteCoords(
      element,
      nextWidth,
      nextHeight,
      false,
    );
    const deltaX1 = (x1 - nextX1) / 2;
    const deltaY1 = (y1 - nextY1) / 2;
    const deltaX2 = (x2 - nextX2) / 2;
    const deltaY2 = (y2 - nextY2) / 2;
    const [nextElementX, nextElementY] = adjustXYWithRotation(
      getSidesForTransformHandle(transformHandleType, shouldResizeFromCenter),
      element.x,
      element.y,
      element.angle,
      deltaX1,
      deltaY1,
      deltaX2,
      deltaY2,
    );
    mutateElement(element, {
      fontSize: nextFontSize,
      width: nextWidth,
      height: nextHeight,
      x: nextElementX,
      y: nextElementY,
    });
  }
};

export const resizeSingleElement = (
  originalElements: PointerDownState["originalElements"],
  shouldMaintainAspectRatio: boolean,
  element: NonDeletedExcalidrawElement,
  transformHandleDirection: TransformHandleDirection,
  shouldResizeFromCenter: boolean,
  pointerX: number,
  pointerY: number,
) => {
  const stateAtResizeStart = originalElements.get(element.id)!;
  // Gets bounds corners
  const [x1, y1, x2, y2] = getResizedElementAbsoluteCoords(
    stateAtResizeStart,
    stateAtResizeStart.width,
    stateAtResizeStart.height,
    true,
  );
  const startTopLeft: Point = [x1, y1];
  const startBottomRight: Point = [x2, y2];
  const startCenter: Point = centerPoint(startTopLeft, startBottomRight);

  // Calculate new dimensions based on cursor position
  const rotatedPointer = rotatePoint(
    [pointerX, pointerY],
    startCenter,
    -stateAtResizeStart.angle,
  );

  // Get bounds corners rendered on screen
  const [esx1, esy1, esx2, esy2] = getResizedElementAbsoluteCoords(
    element,
    element.width,
    element.height,
    true,
  );

  const boundsCurrentWidth = esx2 - esx1;
  const boundsCurrentHeight = esy2 - esy1;

  // It's important we set the initial scale value based on the width and height at resize start,
  // otherwise previous dimensions affected by modifiers will be taken into account.
  const atStartBoundsWidth = startBottomRight[0] - startTopLeft[0];
  const atStartBoundsHeight = startBottomRight[1] - startTopLeft[1];
  let scaleX = atStartBoundsWidth / boundsCurrentWidth;
  let scaleY = atStartBoundsHeight / boundsCurrentHeight;

  let boundTextFont: { fontSize?: number } = {};
  const boundTextElement = getBoundTextElement(element);

  if (transformHandleDirection.includes("e")) {
    scaleX = (rotatedPointer[0] - startTopLeft[0]) / boundsCurrentWidth;
  }
  if (transformHandleDirection.includes("s")) {
    scaleY = (rotatedPointer[1] - startTopLeft[1]) / boundsCurrentHeight;
  }
  if (transformHandleDirection.includes("w")) {
    scaleX = (startBottomRight[0] - rotatedPointer[0]) / boundsCurrentWidth;
  }
  if (transformHandleDirection.includes("n")) {
    scaleY = (startBottomRight[1] - rotatedPointer[1]) / boundsCurrentHeight;
  }

  // Linear elements dimensions differ from bounds dimensions
  const eleInitialWidth = stateAtResizeStart.width;
  const eleInitialHeight = stateAtResizeStart.height;
  // We have to use dimensions of element on screen, otherwise the scaling of the
  // dimensions won't match the cursor for linear elements.
  let eleNewWidth = element.width * scaleX;
  let eleNewHeight = element.height * scaleY;

  // adjust dimensions for resizing from center
  if (shouldResizeFromCenter) {
    eleNewWidth = 2 * eleNewWidth - eleInitialWidth;
    eleNewHeight = 2 * eleNewHeight - eleInitialHeight;
  }

  // adjust dimensions to keep sides ratio
  if (shouldMaintainAspectRatio) {
    const widthRatio = Math.abs(eleNewWidth) / eleInitialWidth;
    const heightRatio = Math.abs(eleNewHeight) / eleInitialHeight;
    if (transformHandleDirection.length === 1) {
      eleNewHeight *= widthRatio;
      eleNewWidth *= heightRatio;
    }
    if (transformHandleDirection.length === 2) {
      const ratio = Math.max(widthRatio, heightRatio);
      eleNewWidth = eleInitialWidth * ratio * Math.sign(eleNewWidth);
      eleNewHeight = eleInitialHeight * ratio * Math.sign(eleNewHeight);
    }
  }

  if (boundTextElement) {
    const stateOfBoundTextElementAtResize = originalElements.get(
      boundTextElement.id,
    ) as typeof boundTextElement | undefined;
    if (stateOfBoundTextElementAtResize) {
      boundTextFont = {
        fontSize: stateOfBoundTextElementAtResize.fontSize,
      };
    }
    if (shouldMaintainAspectRatio) {
      const updatedElement = {
        ...element,
        width: eleNewWidth,
        height: eleNewHeight,
      };

      const nextFontSize = measureFontSizeFromWidth(
        boundTextElement,
        getMaxContainerWidth(updatedElement),
      );
      if (nextFontSize === null) {
        return;
      }
      boundTextFont = {
        fontSize: nextFontSize,
      };
    } else {
      const minWidth = getApproxMinLineWidth(getFontString(boundTextElement));
      const minHeight = getApproxMinLineHeight(getFontString(boundTextElement));
      eleNewWidth = Math.ceil(Math.max(eleNewWidth, minWidth));
      eleNewHeight = Math.ceil(Math.max(eleNewHeight, minHeight));
    }
  }

  const [newBoundsX1, newBoundsY1, newBoundsX2, newBoundsY2] =
    getResizedElementAbsoluteCoords(
      stateAtResizeStart,
      eleNewWidth,
      eleNewHeight,
      true,
    );
  const newBoundsWidth = newBoundsX2 - newBoundsX1;
  const newBoundsHeight = newBoundsY2 - newBoundsY1;

  // Calculate new topLeft based on fixed corner during resize
  let newTopLeft = [...startTopLeft] as [number, number];
  if (["n", "w", "nw"].includes(transformHandleDirection)) {
    newTopLeft = [
      startBottomRight[0] - Math.abs(newBoundsWidth),
      startBottomRight[1] - Math.abs(newBoundsHeight),
    ];
  }
  if (transformHandleDirection === "ne") {
    const bottomLeft = [startTopLeft[0], startBottomRight[1]];
    newTopLeft = [bottomLeft[0], bottomLeft[1] - Math.abs(newBoundsHeight)];
  }
  if (transformHandleDirection === "sw") {
    const topRight = [startBottomRight[0], startTopLeft[1]];
    newTopLeft = [topRight[0] - Math.abs(newBoundsWidth), topRight[1]];
  }

  // Keeps opposite handle fixed during resize
  if (shouldMaintainAspectRatio) {
    if (["s", "n"].includes(transformHandleDirection)) {
      newTopLeft[0] = startCenter[0] - newBoundsWidth / 2;
    }
    if (["e", "w"].includes(transformHandleDirection)) {
      newTopLeft[1] = startCenter[1] - newBoundsHeight / 2;
    }
  }

  // Flip horizontally
  if (eleNewWidth < 0) {
    if (transformHandleDirection.includes("e")) {
      newTopLeft[0] -= Math.abs(newBoundsWidth);
    }
    if (transformHandleDirection.includes("w")) {
      newTopLeft[0] += Math.abs(newBoundsWidth);
    }
  }
  // Flip vertically
  if (eleNewHeight < 0) {
    if (transformHandleDirection.includes("s")) {
      newTopLeft[1] -= Math.abs(newBoundsHeight);
    }
    if (transformHandleDirection.includes("n")) {
      newTopLeft[1] += Math.abs(newBoundsHeight);
    }
  }

  if (shouldResizeFromCenter) {
    newTopLeft[0] = startCenter[0] - Math.abs(newBoundsWidth) / 2;
    newTopLeft[1] = startCenter[1] - Math.abs(newBoundsHeight) / 2;
  }

  // adjust topLeft to new rotation point
  const angle = stateAtResizeStart.angle;
  const rotatedTopLeft = rotatePoint(newTopLeft, startCenter, angle);
  const newCenter: Point = [
    newTopLeft[0] + Math.abs(newBoundsWidth) / 2,
    newTopLeft[1] + Math.abs(newBoundsHeight) / 2,
  ];
  const rotatedNewCenter = rotatePoint(newCenter, startCenter, angle);
  newTopLeft = rotatePoint(rotatedTopLeft, rotatedNewCenter, -angle);

  // Readjust points for linear elements
  let rescaledElementPointsY;
  let rescaledPoints;

  if (isLinearElement(element) || isFreeDrawElement(element)) {
    rescaledElementPointsY = rescalePoints(
      1,
      eleNewHeight,
      (stateAtResizeStart as ExcalidrawLinearElement).points,
      true,
    );

    rescaledPoints = rescalePoints(
      0,
      eleNewWidth,
      rescaledElementPointsY,
      true,
    );
  }

  // For linear elements (x,y) are the coordinates of the first drawn point not the top-left corner
  // So we need to readjust (x,y) to be where the first point should be
  const newOrigin = [...newTopLeft];
  newOrigin[0] += stateAtResizeStart.x - newBoundsX1;
  newOrigin[1] += stateAtResizeStart.y - newBoundsY1;
  const resizedElement = {
    width: Math.abs(eleNewWidth),
    height: Math.abs(eleNewHeight),
    x: newOrigin[0],
    y: newOrigin[1],
    points: rescaledPoints,
  };

  if ("scale" in element && "scale" in stateAtResizeStart) {
    mutateElement(element, {
      scale: [
        // defaulting because scaleX/Y can be 0/-0
        (Math.sign(newBoundsX2 - stateAtResizeStart.x) ||
          stateAtResizeStart.scale[0]) * stateAtResizeStart.scale[0],
        (Math.sign(newBoundsY2 - stateAtResizeStart.y) ||
          stateAtResizeStart.scale[1]) * stateAtResizeStart.scale[1],
      ],
    });
  }

  if (
    resizedElement.width !== 0 &&
    resizedElement.height !== 0 &&
    Number.isFinite(resizedElement.x) &&
    Number.isFinite(resizedElement.y)
  ) {
    updateBoundElements(element, {
      newSize: { width: resizedElement.width, height: resizedElement.height },
    });

    mutateElement(element, resizedElement);
    if (boundTextElement && boundTextFont) {
      mutateElement(boundTextElement, { fontSize: boundTextFont.fontSize });
    }
    handleBindTextResize(element, transformHandleDirection);
  }
};

const resizeMultipleElements = (
  pointerDownState: PointerDownState,
  selectedElements: readonly NonDeletedExcalidrawElement[],
  transformHandleType: "nw" | "ne" | "sw" | "se",
  shouldResizeFromCenter: boolean,
  pointerX: number,
  pointerY: number,
) => {
  // map selected elements to the original elements. While it never should
  // happen that pointerDownState.originalElements won't contain the selected
  // elements during resize, this coupling isn't guaranteed, so to ensure
  // type safety we need to transform only those elements we filter.
  const targetElements = selectedElements.reduce(
    (
      acc: {
        /** element at resize start */
        orig: NonDeletedExcalidrawElement;
        /** latest element */
        latest: NonDeletedExcalidrawElement;
      }[],
      element,
    ) => {
      const origElement = pointerDownState.originalElements.get(element.id);
      if (origElement) {
        acc.push({ orig: origElement, latest: element });
      }
      return acc;
    },
    [],
  );

  const { minX, minY, maxX, maxY, midX, midY } = getCommonBoundingBox(
    targetElements.map(({ orig }) => orig),
  );
  const direction = transformHandleType;

  const mapDirectionsToAnchors: Record<typeof direction, Point> = {
    ne: [minX, maxY],
    se: [minX, minY],
    sw: [maxX, minY],
    nw: [maxX, maxY],
  };

  // anchor point must be on the opposite side of the dragged selection handle
  // or be the center of the selection if alt is pressed
  const [anchorX, anchorY]: Point = shouldResizeFromCenter
    ? [midX, midY]
    : mapDirectionsToAnchors[direction];

  const mapDirectionsToPointerSides: Record<
    typeof direction,
    [x: boolean, y: boolean]
  > = {
    ne: [pointerX >= anchorX, pointerY <= anchorY],
    se: [pointerX >= anchorX, pointerY >= anchorY],
    sw: [pointerX <= anchorX, pointerY >= anchorY],
    nw: [pointerX <= anchorX, pointerY <= anchorY],
  };

  // pointer side relative to anchor
  const [pointerSideX, pointerSideY] = mapDirectionsToPointerSides[
    direction
  ].map((condition) => (condition ? 1 : -1));

  // stop resizing if a pointer is on the other side of selection
  if (pointerSideX < 0 && pointerSideY < 0) {
    return;
  }

  const scale =
    Math.max(
      (pointerSideX * Math.abs(pointerX - anchorX)) / (maxX - minX),
      (pointerSideY * Math.abs(pointerY - anchorY)) / (maxY - minY),
    ) * (shouldResizeFromCenter ? 2 : 1);

  if (scale === 0) {
    return;
  }

  targetElements.forEach((element) => {
    const width = element.orig.width * scale;
    const height = element.orig.height * scale;
    const x = anchorX + (element.orig.x - anchorX) * scale;
    const y = anchorY + (element.orig.y - anchorY) * scale;

    // readjust points for linear & free draw elements
    const rescaledPoints = rescalePointsInElement(
      element.orig,
      width,
      height,
      false,
    );

    const update: {
      width: number;
      height: number;
      x: number;
      y: number;
      points?: Point[];
      fontSize?: number;
    } = {
      width,
      height,
      x,
      y,
      ...rescaledPoints,
    };

    let boundTextUpdates: { fontSize: number } | null = null;

    const boundTextElement = getBoundTextElement(element.latest);

    if (boundTextElement || isTextElement(element.orig)) {
      const updatedElement = {
        ...element.latest,
        width,
        height,
      };
      const fontSize = measureFontSizeFromWidth(
        boundTextElement ?? (element.orig as ExcalidrawTextElement),
        getMaxContainerWidth(updatedElement),
      );

      if (!fontSize) {
        return;
      }

      if (isTextElement(element.orig)) {
        update.fontSize = fontSize;
      }

      if (boundTextElement) {
        boundTextUpdates = {
          fontSize,
        };
      }
    }

    updateBoundElements(element.latest, { newSize: { width, height } });

    mutateElement(element.latest, update);

    if (boundTextElement && boundTextUpdates) {
      mutateElement(boundTextElement, boundTextUpdates);

      handleBindTextResize(element.latest, transformHandleType);
    }
  });
};

const rotateMultipleElements = (
  pointerDownState: PointerDownState,
  elements: readonly NonDeletedExcalidrawElement[],
  pointerX: number,
  pointerY: number,
  shouldRotateWithDiscreteAngle: boolean,
  centerX: number,
  centerY: number,
) => {
  let centerAngle =
    (5 * Math.PI) / 2 + Math.atan2(pointerY - centerY, pointerX - centerX);
  if (shouldRotateWithDiscreteAngle) {
    centerAngle += SHIFT_LOCKING_ANGLE / 2;
    centerAngle -= centerAngle % SHIFT_LOCKING_ANGLE;
  }
  elements.forEach((element) => {
    const [x1, y1, x2, y2] = getElementAbsoluteCoords(element);
    const cx = (x1 + x2) / 2;
    const cy = (y1 + y2) / 2;
    const origAngle =
      pointerDownState.originalElements.get(element.id)?.angle ?? element.angle;
    const [rotatedCX, rotatedCY] = rotate(
      cx,
      cy,
      centerX,
      centerY,
      centerAngle + origAngle - element.angle,
    );
    mutateElement(element, {
      x: element.x + (rotatedCX - cx),
      y: element.y + (rotatedCY - cy),
      angle: normalizeAngle(centerAngle + origAngle),
    });
    const boundTextElementId = getBoundTextElementId(element);
    if (boundTextElementId) {
      const textElement =
        Scene.getScene(element)?.getElement<ExcalidrawTextElementWithContainer>(
          boundTextElementId,
        );
      if (textElement && !isArrowElement(element)) {
        mutateElement(textElement, {
          x: textElement.x + (rotatedCX - cx),
          y: textElement.y + (rotatedCY - cy),
          angle: normalizeAngle(centerAngle + origAngle),
        });
      }
    }
  });
};

export const getResizeOffsetXY = (
  transformHandleType: MaybeTransformHandleType,
  selectedElements: NonDeletedExcalidrawElement[],
  x: number,
  y: number,
): [number, number] => {
  const [x1, y1, x2, y2] =
    selectedElements.length === 1
      ? getElementAbsoluteCoords(selectedElements[0])
      : getCommonBounds(selectedElements);
  const cx = (x1 + x2) / 2;
  const cy = (y1 + y2) / 2;
  const angle = selectedElements.length === 1 ? selectedElements[0].angle : 0;
  [x, y] = rotate(x, y, cx, cy, -angle);
  switch (transformHandleType) {
    case "n":
      return rotate(x - (x1 + x2) / 2, y - y1, 0, 0, angle);
    case "s":
      return rotate(x - (x1 + x2) / 2, y - y2, 0, 0, angle);
    case "w":
      return rotate(x - x1, y - (y1 + y2) / 2, 0, 0, angle);
    case "e":
      return rotate(x - x2, y - (y1 + y2) / 2, 0, 0, angle);
    case "nw":
      return rotate(x - x1, y - y1, 0, 0, angle);
    case "ne":
      return rotate(x - x2, y - y1, 0, 0, angle);
    case "sw":
      return rotate(x - x1, y - y2, 0, 0, angle);
    case "se":
      return rotate(x - x2, y - y2, 0, 0, angle);
    default:
      return [0, 0];
  }
};

export const getResizeArrowDirection = (
  transformHandleType: MaybeTransformHandleType,
  element: NonDeleted<ExcalidrawLinearElement>,
): "origin" | "end" => {
  const [, [px, py]] = element.points;
  const isResizeEnd =
    (transformHandleType === "nw" && (px < 0 || py < 0)) ||
    (transformHandleType === "ne" && px >= 0) ||
    (transformHandleType === "sw" && px <= 0) ||
    (transformHandleType === "se" && (px > 0 || py > 0));
  return isResizeEnd ? "end" : "origin";
};