Trying to select lines or rectangles on a canvas

Question

I want to be able to click any line(muscle) and new line then highlight it in my program like I can do with the nodes right now. I want to use context.isPointInPath(), but I feel like that will be too limiting in the fact that the lines are only 1 pixel wide. And now I want to look at changing the lines to rectangles. Because then I would be able to just see if the mouseclick is within the rectangle height and width. But, I'm having trouble finding out a way to connect the rectangle to two nodes like I have it with the strokes right now. My program so far:

/*jshint esversion: 6 */
//draw everything on canvas
//TODO: Change use of canvas to a container and moving elements around to avoid the buffer of frame drawing

//Node class
class Node {
  constructor(x, y, r, color, highlight, highlightColor) {
    this.x = x;
    this.y = y;
    this.r = r || 20;
    this.color = color || "#ff0";
    this.highlight = highlight || false;
    this.highlightColor = highlightColor || "#0000FF";
  }
}

//Muscle class
class Muscle {
  constructor(node1, node2, width, color) {
    this.node1 = node1;
    this.node2 = node2;
    this.width = width || 5;
    this.color = color || "#f00";


    //Properties of the nodes this muscle attaches to 
    Object.defineProperties(this, {

      node1x: {
        "get": () => this.node1.x,
        "set": x => {
          this.node1.x = x;
        }
      },

      node1y: {
        "get": () => this.node1.y,
        "set": y => {
          this.node1.y = y;
        }
      },

      node2x: {
        "get": () => this.node2.x,
        "set": x => {
          this.node2.x = x;
        }
      },

      node2y: {
        "get": () => this.node2.y,
        "set": y => {
          this.node2.x = y;
        }
      }
    });
  }
}

function setParentForNodes() {
  this.nodes.forEach(node => {
    node.parentCreature = this;
  });
}

class Creature {
  constructor(nodes, muscles, nodeColors) {
    this.nodes = nodes;
    this.muscles = muscles;
    this.nodeColors = nodeColors || "#ff0";
    setParentForNodes.call(this);

    Object.defineProperties(this, {

      creatureNumber: {
        "get": () => creatures.indexOf(this),
      }
    });
  }

  addNewNode(newNode) {
    newNode.parentCreature = this;
    this.nodes.push(newNode);
  }
  addNewNodes(newNodes) {
    newNodes.forEach(function(node) {
      node.parentCreature = this;
    }, this);
    this.nodes = this.nodes.concat(newNodes);
  }
}

var nodes = [
  new Node(100, 100),
  new Node(200, 200)
];

var muscles = [
  new Muscle(nodes[0], nodes[1])
];

var creatures = [
  new Creature(nodes, muscles)
];

var addNodePressed = false;
var attachMusclePressed = false;
var addLimbPressed = false;

function draw(container, ctx, nodes, creatureMuscles) {

  //draw in the container
  ctx.fillStyle = "#000000";
  ctx.fillRect(container.y, container.x, container.width, container.height);

  // for loop to draw all objects of nodes 
  for (let i = 0; i < creatures.length; i++) {

    var creatureNodes = creatures[i].nodes;

    for (let i = 0; i < creatureNodes.length; i++) {
      ctx.beginPath();
      ctx.arc(creatureNodes[i].x, creatureNodes[i].y, creatureNodes[i].r, 0, 2 * Math.PI);
      ctx.fillStyle = creatureNodes[i].color;
      ctx.closePath();
      ctx.fill();

      //check if node needs to be highlighted
      if (creatureNodes[i].highlight == true) {
        ctx.beginPath();
        ctx.arc(creatureNodes[i].x, creatureNodes[i].y, creatureNodes[i].r, 0, 2 * Math.PI);
        ctx.strokeStyle = creatureNodes[i].highlightColor;
        ctx.lineWidth = 5; // for now
        ctx.closePath();
        ctx.stroke();
      }
    }
    creatureMuscles = creatures[i].muscles;
    //loop and draw every muscle
    for (let i = 0; i < creatureMuscles.length; i++) {
      ctx.beginPath();
      ctx.moveTo(creatureMuscles[i].node1x, creatureMuscles[i].node1y);
      ctx.lineTo(creatureMuscles[i].node2x, creatureMuscles[i].node2y);
      ctx.strokeStyle = creatureMuscles[i].color;
      ctx.lineWidth = creatureMuscles[i].width;
      ctx.closePath();
      ctx.stroke();
    }
  }
}

//Handle moving a node with mousedrag
function handleMouseDrag(canvas, creatureNodes) {
  var isDrag = false;
  var dragNode;
  var offset = {
    x: 0,
    y: 0,
    x0: 0,
    y0: 0
  };


  canvas.addEventListener("mousedown", function(e) {
    //mousedown then save the position in var x and y
    var x = e.offsetX,
      y = e.offsetY;

    //loop through all the nodes to find the first node that is within radius of the mouse click
    for (let i = 0; i < creatures.length; i++) {
      var creatureNodes = creatures[i].nodes;

      for (let i = 0; i < creatureNodes.length; i++) {
        if (Math.pow(x - creatureNodes[i].x, 2) + Math.pow(y - creatureNodes[i].y, 2) < Math.pow(creatureNodes[i].r, 2)) {
          isDrag = true;
          dragNode = creatureNodes[i];

          //offset.x&y = where the node is currently
          //offset x0&y0 = where the user clicked
          offset = {
            x: dragNode.x,
            y: dragNode.y,
            x0: x,
            y0: y
          };
          return;
        }
      }
    }
  });
  // when mouse moves and isDrag is true, move the node's position
  canvas.addEventListener("mousemove", function(e) {
    /*when the user moves the mouse, take the difference of where his mouse is right now and where the user clicked.
    Then, add that to where the node is right now to find the correct placement of the node without centering on your mouse 
    */
    if (isDrag) {
      dragNode.x = e.offsetX - offset.x0 + offset.x; // where the mouse is right now - where the user mousedown + where the node is right now
      dragNode.y = e.offsetY - offset.y0 + offset.y;
    }
  });

  canvas.addEventListener("mouseup", function(e) {
    isDrag = false;
  });

  canvas.addEventListener("mouseleave", function(e) {
    isDrag = false;
  });
}

//Handle highlighting and button functionality
function handleMouseClick(canvas, nodes, muscles) {
  var highlighted;
  var highlightedNode;

  canvas.addEventListener("mousedown", function(e) {
    var x = e.offsetX,
      y = e.offsetY;

    var loopbreak = false;

    for (let i = 0; i < creatures.length; i++) {

      var creatureNodes = creatures[i].nodes;

      for (let i = 0; i < creatureNodes.length; i++) {
        // check if click is within radius of a node, if it is, highlight and set highlight boolean to true.

        if (Math.pow(x - creatureNodes[i].x, 2) + Math.pow(y - creatureNodes[i].y, 2) < Math.pow(creatureNodes[i].r, 2)) {
          var clickedNode = creatureNodes[i];

          if (addNodePressed) {
            console.log("Not valid. Cannot add a node on top of another node.");
            loopbreak = true;
            break;
          } else if (addLimbPressed) {
            console.log("Not valid. Cannot add a limb on top of another node.");
            loopbreak = true;
            break;
          } else if (attachMusclePressed) {
            if (highlightedNode == clickedNode) {
              console.log("Not valid. Cannot attach muscle to the same node.");
              loopbreak = true;
              break;
            } else {
              var newMuscle;

              if (highlightedNode.parentCreature.creatureNumber == clickedNode.parentCreature.creatureNumber) {
                newMuscle = new Muscle(highlightedNode, clickedNode);
                highlightedNode.parentCreature.muscles.push(newMuscle);
                attachMuscle();
                highlightedNode.highlight = false;
                highlighted = false;
                devTools(true, false, false, false);
              } else {
                var newNodes = [];
                var newMuscles = [];

                if (highlightedNode.parentCreature.creatureNumber > clickedNode.parentCreature.creatureNumber) {
                  highlightedNode.parentCreature.nodes.forEach(function(node) {
                    newNodes.push(node);
                  });
                  highlightedNode.parentCreature.muscles.forEach(function(muscle) {
                    newMuscles.push(muscle);
                  });
                  newMuscle = new Muscle(highlightedNode, clickedNode);
                  clickedNode.parentCreature.muscles.push(newMuscle);
                  clickedNode.parentCreature.muscles = clickedNode.parentCreature.muscles.concat(newMuscles);
                  creatures.splice(creatures.indexOf(highlightedNode.parentCreature), 1);
                  clickedNode.parentCreature.addNewNodes(newNodes);
                } else {
                  clickedNode.parentCreature.nodes.forEach(function(node) {
                    newNodes.push(node);
                    console.log("Clicked node is bigger.");
                  });
                  clickedNode.parentCreature.muscles.forEach(function(muscle) {
                    newMuscles.push(muscle);
                  });
                  newMuscle = new Muscle(highlightedNode, clickedNode);
                  highlightedNode.parentCreature.muscles.push(newMuscle);
                  highlightedNode.parentCreature.muscles = highlightedNode.parentCreature.muscles.concat(newMuscles);
                  creatures.splice(creatures.indexOf(clickedNode.parentCreature), 1);
                  highlightedNode.parentCreature.addNewNodes(newNodes);
                }
                highlightedNode.highlight = false;
                attachMuscle();
                devTools(true, false, false, false);
              }
            }
          }
          //no button pressed - highlight/unhighlight node
          else {
            if (highlighted || creatureNodes[i].highlight) {
              if (highlightedNode != creatureNodes[i]) {
                highlightedNode.highlight = false;
                highlightedNode = creatureNodes[i];
                highlightedNode.highlight = true;
                devTools(false, true, true, true);
              } else {
                highlightedNode = creatureNodes[i];
                highlightedNode.highlight = false;
                highlighted = false;
                highlightedNode = undefined;
                devTools(true, false, false, false);
              }
            } else {
              highlightedNode = creatureNodes[i];
              highlightedNode.highlight = true;
              highlighted = true;
              devTools(false, true, true, true);
            }
            loopbreak = true;
            break;
          }
        }
      }
    }

    // if click was not in radius of any nodes then check for add limb or create node button press. 
    if (!loopbreak) {
      loopbreak = false;
      var newNode;
      if (addNodePressed) {
        newNode = new Node(x, y);
        let newNodes = [];
        let newMuscles = [];
        newNodes.push(newNode);
        var newCreature = new Creature(newNodes, newMuscles);
        creatures.push(newCreature);
        addNode();
        addNodePressed = false;
        devTools(true, false, false, false);
      } else if (addLimbPressed) {
        newNode = new Node(x, y);
        let newMuscle = new Muscle(newNode, highlightedNode);
        highlightedNode.parentCreature.addNewNode(newNode);
        highlightedNode.parentCreature.muscles.push(newMuscle);
        addLimb();
        addLimbPressed = false;
        highlightedNode.highlight = false;
        highlighted = false;
        highlightedNode = undefined;
        devTools(true, false, false, false);
      }
    }
  });
}

//Handle Devtools
function devTools(addNode, removeNode, attachMuscle, addLimb) {

  var creatureNumberHTML = document.getElementById("creatureNumber");
  var selectedHTML = document.getElementById("selected");
  var addNodeB = document.getElementById("addNode");
  var removeNodeB = document.getElementById("removeNode");
  var attachMuscleB = document.getElementById("attachMuscle");
  var addLimbB = document.getElementById("addLimb");

  addNodeB.disabled = (addNode) ? false : true;
  removeNodeB.disabled = (removeNode) ? false : true;
  attachMuscleB.disabled = (attachMuscle) ? false : true;
  addLimbB.disabled = (addLimb) ? false : true;

  for (let i = 0; i < creatures.length; i++) {
    var creatureNumber = i;
    var creatureNodes = creatures[i].nodes;

    for (let i = 0; i < creatureNodes.length; i++) {
      if (creatureNodes[i].highlight == true) {
        selectedHTML.innerHTML = `Selected: ${i} node`;
        creatureNumberHTML.innerHTML = `Creature number: ${creatureNumber}`;
        return;
      } else {
        creatureNumberHTML.innerHTML = "Creature number: -";
        selectedHTML.innerHTML = "Selected: None";
      }
    }
  }
}

//Handle add node button
function addNode() {
  var addNodeB = document.getElementById("addNode");

  if (addNodePressed) {
    addNodePressed = false;
    addNodeB.style.background = "";
  } else {
    addNodePressed = true;
    addNodeB.style.backgroundColor = "#808080";
    //and unhighlight
  }
}

//Handle remove node button
function removeNode() {
  for (let i = 0; i < creatures.length; i++) {
    var creatureNodes = creatures[i].nodes;
    var creatureMuscles = creatures[i].muscles;

    for (let i = 0; i < creatureNodes.length; i++) {
      if (creatureNodes[i].highlight == true) {

        let highlightedNode = creatureNodes[i];

        for (let i = 0; i < creatureMuscles.length; i++) {
          if (creatureMuscles[i].node1 == highlightedNode || creatureMuscles[i].node2 == highlightedNode) {
            creatureMuscles.splice(i, 1);
            i--;
          }
        }
        creatureNodes.splice(i, 1);
      }
    }
  }
  devTools(true, false, false, false);
}

//Handle attach muscle button
function attachMuscle() {
  var attachMuscleB = document.getElementById("attachMuscle");

  if (attachMusclePressed) {
    attachMusclePressed = false;
    attachMuscleB.style.background = "";
  } else {
    attachMusclePressed = true;
    attachMuscleB.style.backgroundColor = "#808080";
  }
}

//Handle add limb button 
function addLimb() {
  var addLimbB = document.getElementById("addLimb");

  if (addLimbPressed) {
    addLimbPressed = false;
    addLimbB.style.background = "";
  } else {
    addLimbPressed = true;
    addLimbB.style.backgroundColor = "#808080";
  }
}

//Main - Grabs document elements to draw a canvas on, init node and muscle arrays and then continuously updates frame to redraw
function main() {
  var canvas = document.getElementById("canvas");
  var ctx = canvas.getContext("2d");
  var container = {
    x: 0,
    y: 0,
    get width() {
      return canvas.width;
    },
    get height() {
      return canvas.height;
    }
  };

  handleMouseDrag(canvas, nodes);
  handleMouseClick(canvas, nodes, muscles);
  // refresh and redraw with new properties in an updateframe infinite loop
  function updateFrame() {
    ctx.save();
    draw(container, ctx, nodes, muscles);
    ctx.restore();
    requestAnimationFrame(updateFrame);
  }
  updateFrame();
}

main();

#canvas {
  display: block;
}

#info {
  display: inline-block;
  text-overflow: clip;
  overflow: hidden;
  margin-right: 200px;
}

#commands {
  display: inline-block;
  text-align: center;
  margin-left: 200px;
}

#devTools {
  background-color: aqua;
  width: 1500px;
}

section {
  width: 200px;
  height: 200px;
  background-color: grey;
  vertical-align: top;
}

<!DOCTYPE HTML>

<html>

<head>
  <meta charset="UTF-8">
  <link rel="stylesheet" type="text/css" href="styles.css" />
</head>

<body>
  <!--TODO: Adjust the size of the canvas to fit the window-->
  <canvas id="canvas" width="1500" , height="600"></canvas>

  <!--TODO: Create buttons for all devtools under the canvas-->
  <!--TODO: Make a container for all devtools under the canvas, then add all the functionality to it after-->
  <div id="devTools">
    <section id="info">
      <p>Info</p>
      <p id="creatureNumber">Creature Number: -</p>
      <p id="selected">Selected: </p>
    </section>

    <section id="commands">
      <p>Commands</p>
      <button type="button" id="addNode" onclick="addNode()">Add node</button>
      <button type="button" id="removeNode" disabled=true onclick="removeNode()">Remove node</button>
      <button type="button" id="attachMuscle" disabled=true onclick="attachMuscle()">Attach muscle</button>
      <button type="button" id="addLimb" disabled=true onclick="addLimb()">Add Limb</button>
      <div id="muscleLength">
        <button type="button" id="increaseLengthB">&uarr;</button>
        <p>Muscle Length</p>
        <button type="button" id="decreaseLengthB">&darr;</button>
      </div>



    </section>
  </div>

  <script src="scripts/script.js"></script>
</body>

</html>

Answer 1

Another way to solve this is to use a thicker line-width and use isPointInStroke() instead.

var ctx = c.getContext("2d");
var path = new Path2D();                           // to store and reuse path
var onLine = false;                                // state (for demo)
path.moveTo(10, 10);                               // store a line on path
path.lineTo(200, 100);
ctx.lineWidth = 16;                                // line width
render();                                          // initial render

function render() {
  ctx.clearRect(0,0,300,150);
  ctx.strokeStyle = onLine ? "#09f" : "#000";      // color based on state
  ctx.stroke(path);                                // stroke path
}

c.onmousemove = function(e) {                      // demo: is mouse on stroke?
  onLine = ctx.isPointInStroke(path, e.clientX, e.clientY);
  render();
};

body, html {margin:0}

<canvas id=c></canvas>

Note: IE11 does not support the path argument - for it you will need to use ordinary path on the context itself (ctx.moveTo etc.)