obsidian-excalidraw-plugin/ea-scripts/Boolean Operations.md

/* With This Script it is possible to make boolean Operations on Shapes.

See documentation for more details: https://zsviczian.github.io/obsidian-excalidraw-plugin/ExcalidrawScriptsEngine.html

*/
const PolyBool = ea.getPolybool();
const polyboolAction = await utils.suggester(["union (a + b)", "intersect (a && b)", "diffrence (a - b)", "reversed diffrence (b - a)", "xor"], [
  PolyBool.union, PolyBool.intersect, PolyBool.difference, PolyBool.differenceRev, PolyBool.xor
], "What would you like todo with the object");

const elements = ea.getViewSelectedElements();
const shadowClones = elements.filter(element => element.isShadowCloneOf);
shadowClones.forEach(shadowClone => {
  const shadowCloneIndex = elements.findIndex(element => element.id = shadowClone.isShadowCloneOf);
  if (shadowCloneIndex == -1) return;
  elements[shadowCloneIndex].backgroundColor = shadowClone.backgroundColor;
})
const borderElements = elements.filter(element => !element.isShadowCloneOf);
groups = ea.getMaximumGroups(borderElements);
groups = groups.map((group) => group.sort((a, b) => RankElement(b) - RankElement(a)));
groups.sort((a, b) => RankElement(b[0]) - RankElement(a[0]));

ea.style.strokeColor = groups[0][0].strokeColor;
ea.style.backgroundColor = groups[0][0].backgroundColor;
ea.style.fillStyle = groups[0][0].fillStyle;
ea.style.strokeWidth = groups[0][0].strokeWidth;
ea.style.strokeStyle = groups[0][0].strokeStyle;
ea.style.roughness = groups[0][0].roughness;
ea.style.opacity = groups[0][0].opacity;

const basePolygons = groups.shift().map(element => traceElement(element));
const toolPolygons = groups.flatMap(group => group.map(element => traceElement(element)));

const result = polyboolAction({
  regions: basePolygons,
  inverted: false
}, {
  regions: toolPolygons,
  inverted: false
});
const polygonHierachy = subordinateInnerPolygons(result.regions);
drawPolygonHierachy(polygonHierachy);
ea.deleteViewElements(elements);
ea.addElementsToView(false,false,true);
// return;



function traceElement(element) {
  const diamondPath = (diamond) => [
      SxVEC(1/2, [0, diamond.height]),
      SxVEC(1/2, [diamond.width, 0]),
      addVec([SxVEC(1/2, [0, diamond.height]), ([diamond.width, 0])]),
      addVec([SxVEC(1/2, [diamond.width, 0]), ([0, diamond.height])]),
      SxVEC(1/2, [0, diamond.height])
    ];
  const rectanglePath = (rectangle) => [
    [0,0],
    [0, rectangle.height],
    [rectangle.width, rectangle.height],
    [rectangle.width, 0],
    [0, 0]
  ]
  const ellipsePath = (ellipse) => {
    const angle = ellipse.angle;
    const width = ellipse.width;
    const height = ellipse.height;
    const ellipseAtPoint = (t) => {
      const spanningVector = [width/2*Math.cos(t), height/2*Math.sin(t)];
      const baseVector = [width/2, height/2];
      return addVec([spanningVector, baseVector]);
    }
    let points = [];
    step = (2*Math.PI)/64
    for (let t = 0; t < 2*Math.PI; t = t + step) {
      points.push(ellipseAtPoint(t));
    }
    return points;
  }
  let polygon;
  let correctForPolygon = [0, 0];
  switch (element.type) {
    case "diamond":
      polygon = diamondPath(element);
      break;
    case "rectangle":
      polygon = rectanglePath(element);
      break;
    case "ellipse":
      polygon = ellipsePath(element);
      break;
    case "line":
    case "arrow":
      if (element.angle != 0) {
        let smallestX = 0;
        let smallestY = 0;
        element.points.forEach(point => {
          if (point[0] < smallestX) smallestX = point[0];
          if (point[1] < smallestY) smallestY = point[1];
        });
        polygon = element.points.map(point => {
          return [
            point[0] -= smallestX,
            point[1] -= smallestY
          ];
        });
        correctForPolygon = [smallestX, smallestY];
        break;
      }
      if (element.roundness) {
        new Notice("This script does not work with curved lines or arrows yet!");
        return [];
      }
      polygon = element.points; 
      default:
          break;
    }
  if (element.angle == 0) return polygon.map(v => addVec([v, [element.x, element.y]]));
  
  polygon = polygon.map(v => addVec([v, SxVEC(-1/2, [element.width, element.height])]));
  polygon = rotateVectorsByAngle(polygon, element.angle);
  return polygon.map(v => addVec([v, [element.x, element.y], SxVEC(1/2, [element.width, element.height]), correctForPolygon]));
}

function RankElement(element) {
  let score = 0;
  const backgroundRank = [
    "dashed",
    "none",
    "hachure",
    "zigzag",
    "zigzag-line",
    "cross-hatch",
    "solid"
  ]
  score += (backgroundRank.findIndex((fillStyle) => fillStyle == element.fillStyle) + 1) * 10;
  if (element.backgroundColor == "transparent") score -= 100;
  if (element.points && getVectorLength(element.points[element.points.length - 1]) > 8) score -= 100; 
  if (score < 0) score = 0;
  score += element.opacity / 100;
  return score;
}

function drawPolygonHierachy(polygonHierachy) {
  const backgroundColor = ea.style.backgroundColor;
  const strokeColor = ea.style.strokeColor;
  const setInnerStyle = () => {
    ea.style.backgroundColor = backgroundColor;
    ea.style.strokeColor = "transparent";
  }
  const setBorderStyle = () => {
    ea.style.backgroundColor = "transparent";
    ea.style.strokeColor = strokeColor;
  }
  const setFilledStyle = () => {
    ea.style.backgroundColor = backgroundColor;
    ea.style.strokeColor = strokeColor;
  }
  
  let gatheredIds = [];
  polygonHierachy.forEach(polygon => {
    let path = polygon.path;
    path.push(polygon.path[0]);
    if (polygon.innerPolygons.length === 0) {
      setFilledStyle();
      ea.addLine(path);
      return;
    }
    const outerBorder = path;
    const innerPolygons = addInnerPolygons(polygon.innerPolygons);
    path = path.concat(innerPolygons.backgroundPath);
    path.push(polygon.path[0]);
    setInnerStyle();
    const backgroundId = ea.addLine(path);
    setBorderStyle();
    const outerBorderId = ea.addLine(outerBorder)
    const background = ea.getElement(backgroundId);
    background.isShadowCloneOf = outerBorderId;
    const innerBorderIds = innerPolygons.borderPaths.map(path => ea.addLine(path));
    const allIds = [innerBorderIds, outerBorderId, backgroundId].flat();
    gatheredIds = gatheredIds.concat(allIds);
    ea.addToGroup(allIds);
  });
  ea.addToGroup(gatheredIds);
}

function addInnerPolygons(polygonHierachy) {
  let firstPath = [];
  let secondPath = [];
  let borderPaths = [];
  polygonHierachy.forEach(polygon => {
    let path = polygon.path;
    path.push(polygon.path[0]);
    borderPaths.push(path);
    firstPath = firstPath.concat(path);
    secondPath.push(polygon.path[0]);
  });
  return {
    backgroundPath: firstPath.concat(secondPath), 
    borderPaths: borderPaths
  };
}

function subordinateInnerPolygons(polygons) {
  const polygonObjectPrototype = (polygon) => {
    return {
      path: polygon,
      innerPolygons: []
    };
  }

  const insertPolygonIntoHierachy = (polygon, hierarchy) => {
    for (let i = 0; i < hierarchy.length; i++) {
      const polygonObject = hierarchy[i];
      let inside = null;
      let pointIndex = 0;
      do {
        inside = pointInPolygon(polygon[pointIndex], polygonObject.path);
        pointIndex++
      } while (inside === null);
      if (inside) {
        hierarchy[i].innerPolygons = insertPolygonIntoHierachy(polygon, hierarchy[i].innerPolygons);
        return hierarchy;
      }
    }
    polygon = polygonObjectPrototype(polygon);
    for (let i = 0; i < hierarchy.length; i++) {
      const polygonObject = hierarchy[i];
      let inside = null;
      let pointIndex = 0;
      do {
        inside = pointInPolygon(polygonObject.path[pointIndex], polygon.path);
        pointIndex++
      } while (inside === null);
      if (inside) {
        polygon.innerPolygons.push(hierarchy.splice(i, 1)[0]);
        i--;
      }
    }
    hierarchy.push(polygon);
    return hierarchy;
  }

  let polygonHierachy = [];
  polygons.forEach(polygon => {
    polygonHierachy = insertPolygonIntoHierachy(polygon, polygonHierachy);
  })

  return polygonHierachy;
}

/**
 * Checks if the given point lays in the polygon
 * @param point array [x, y]
 * @param polygon array [[x, y], ...]
 * @returns true if inside, false if not, null if the point is on one of the polygons vertecies
 */
function pointInPolygon(point, polygon) {
  const x = point[0];
  const y = point[1];
  let inside = false;

  // odd even test if point is in polygon
  for (let i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
    const xi = polygon[i][0];
    const yi = polygon[i][1];
    const xj = polygon[j][0];
    const yj = polygon[j][1];

    const intersect =
      yi > y !== yj > y &&
      x < ((xj - xi) * (y - yi)) / (yj - yi) + xi;

    if (intersect) {
      inside = !inside;
    }

    if ((x === xi && y === yi) || (x === xj && y === yj)) {
      return null;
    }
  }

  return inside;
}


function getVectorLength(vector) {
  return Math.sqrt(vector[0]**2+vector[1]**2);
}

/**
 * Adds two Vectors together
 */
function addVec(vectors) {
  return vectors.reduce((acc, vec) => [acc[0] + vec[0], acc[1] + vec[1]], [0, 0]);
}

/**
 * Returns the negative of the vector
 */
function negVec(vector) {
  return [-vector[0], -vector[1]];
}
 
/**
 * Multiplies Vector with a scalar
 */
function SxVEC(scalar, vector) {
  return [vector[0] * scalar, vector[1] * scalar];
}

function rotateVector (vec, ang)  {
  var cos = Math.cos(ang);
  var sin = Math.sin(ang);
  return [vec[0] * cos - vec[1] * sin, vec[0] * sin + vec[1] * cos];
}

function rotateVectorsByAngle(vectors, angle) {
  const cosAngle = Math.cos(angle);
  const sinAngle = Math.sin(angle);

  const rotationMatrix = [
    [cosAngle, -sinAngle],
    [sinAngle, cosAngle]
  ];

  return applyTranformationMatrix(vectors, rotationMatrix);
}

function applyTranformationMatrix(vectors, transformationMatrix) {
  const result = [];
  for (const vector of vectors) {
    const x = vector[0];
    const y = vector[1];

    const newX = transformationMatrix[0][0] * x + transformationMatrix[0][1] * y;
    const newY = transformationMatrix[1][0] * x + transformationMatrix[1][1] * y;

    result.push([newX, newY]);
  }

  return result;
}