Javascript 判断鼠标是否在具有三个 x,y 坐标的三角形中

let x1, y1, x2, y2, x3, y3;    
let Size, x, y, moving;

//runs once at the start of the program
function setup() {
  
  createCanvas(400, 400);
  
  Size = 100;
  x = 10;
  y = 10;
  moving = false;
  
}
//runs once every frame
function draw() {
  
  background(220);
  handleMouse();
  
  fill("grey");
  noStroke();
  square(x, y, Size, 5);
  fill("black");
  
  x1 = x + Size * 0.9;
  y1 = y + Size * 0.9;
  x2 = x + Size * 0.7;
  y2 = y + Size * 0.9;
  x3 = x + Size * 0.9;
  y3 = y + Size * 0.7;
  triangle(x1, y1, x2, y2, x3, y3);
  
}

function handleMouse(){
    if(mouseIsPressed && (moving || mouseInTriangle(x1, y1, x2, y2, x3, y3))) {
        moving = true;
        Size = max((mouseX + mouseY)/2 + x + y, 50);
    } else {
        moving = false;
    }
}

function getArea(a, b, c) {
    return abs((a[0]*(b[1]-c[1]) + b[0]*(c[1]-a[1])+ c[0]*(a[1]-b[1]))/2);
}

function mouseInTriangle(x1, y1, x2, y2, x3, y3){
    let point = [mouseX, mouseY];
    let area = getArea([x1, y1], [x2, y2], [x3, y3]);
    let areaA = getArea([x1, y1], [x2, y2], point);
    let areaB = getArea(point, [x2, y2], [x3, y3]);
    let areaC = getArea([x1, y1], point, [x3, y3]);
    return abs(areaA + areaB + areaC - area) < 0.001;
}

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