单击鼠标在多个对象上选择Fabricjs

Question

Any suggestion on select multi objects on canvas mouse click? not all object, I want to select objects that overlay on the point.

For my knowledge, the target on mouse event is always the top most object only. I had tried to bind event on object, but it wont fired for those at the back side. I had tried select based on item size and height, but it is not working perfectly after rotate.

var canvas = this.__canvas = new fabric.Canvas('c', {
  enableRetinaScaling: false
});

function LoopOnObjects(e) {
  var mouse = canvas.getPointer(e.e, false);
  var x = Math.ceil(mouse.x);
  var y = Math.ceil(mouse.y);

  var count = 0;
  canvas.getObjects().forEach(function(object, index){
    if(CheckObjectWithin(object, x, y)) {
        count++;
    }
  });

  alert("ya, there is " + count + " objects touch on click");
}

function CheckObjectWithin(object, x, y) {
    var objectBoundRect = object.getBoundingRect(true);
    var widthRange = objectBoundRect.width;
    var heightRange = objectBoundRect.height;

    if (x > objectBoundRect.left && x < objectBoundRect.left + widthRange) {
        if (y > objectBoundRect.top && y < objectBoundRect.top + heightRange) {
            return true;
        }
    }

    return false;
}

function GetElement(e) {
    LoopOnObjects(e);
}

canvas.on("mouse:up", GetElement);

canvas.add(new fabric.Rect({
    width: 100, height: 100, left: 100, top: 20, angle: -10,
    fill: 'rgba(0,200,0,0.5)'
  }));
canvas.add(new fabric.Rect({
    width: 50, height: 100, left: 220, top: 80, angle: 45,
    stroke: '#eee', strokeWidth: 10,
    fill: 'rgba(0,0,200,0.5)'
  }));
canvas.add(new fabric.Circle({
    radius: 50, left: 220, top: 175, fill: '#aac'
  }));

template for testing

Answer 1

Actually, there is already a library method for that: fabric.Object.prototype.containsPoint() . It works with rotate, but keep in mind that the point is checked against the bounding box, not the visible shape (eg circle shape still has a rectangular bounding box).

 var canvas = this.__canvas = new fabric.Canvas('c'); function loopOnObjects(e) { var mouse = canvas.getPointer(ee, false); var point = new fabric.Point(mouse.x, mouse.y) var count = 0; canvas.getObjects().forEach(function(object, index){ if (object.containsPoint(point)) { count++; } }); } function getElement(e) { loopOnObjects(e); } canvas.on("mouse:down", getElement); canvas.add(new fabric.Rect({ width: 100, height: 100, left: 100, top: 20, angle: -10, fill: 'rgba(0,200,0,0.5)' })); canvas.add(new fabric.Rect({ width: 50, height: 100, left: 220, top: 80, angle: 45, stroke: '#eee', strokeWidth: 10, fill: 'rgba(0,0,200,0.5)' })); canvas.add(new fabric.Circle({ radius: 50, left: 220, top: 175, fill: '#aac' })); 

 #c { border: 1px black solid; } 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.22/fabric.min.js"></script> <canvas id="c" width="500" height="300"></canvas>