Change control fill color while scaling object in Fabricjs

Question

For a few days now, I have been trying to change the fill color of the control that is scaling an object.

Here is a gif of what I'm talking about:

I would like some guidance on how to achieve this. I have been digging through Fabricjs documentation for days trying to get an idea on how to approach this problem.

https://github.com/fabricjs/fabric.js/wiki/Working-with-events

My theory was to bind to mouse:down and mouse:up events. When mouse:down event fires, obtain the control context and change its fill color and when the mouse:up fires, restore the fill color.

Unfortunately, I can't find any fabricjs method that would allow me to obtain the control context.

http://fabricjs.com/docs/fabric.Canvas.html

http://fabricjs.com/docs/fabric.Object.html

    canvas.on('mouse:down',(){
     // Obtain control context and change fill

    });
    canvas.on('mouse:up',(){
    // Obtain control context and restore fill

    });

I'm using Fabricjs version 3.2.0

Answer 1

I overwrote the _drawControl from fabric.Object. As you can see I verified this.__corner control variable, If are equal I changed the fill and stroke color to red. Very important I restored the context after I drawn the control

var canvas = new fabric.Canvas('fabriccanvas');
canvas.add(new fabric.Rect({
        top: 50,
        left: 50 ,
        width: 100,
        height: 100,
        fill: '#' + (0x1000000 + (Math.random()) * 0xffffff).toString(16).substr(1, 6),
        //fix attributes applied for all rects
       cornerStyle:"circle",
        originX: 'left',
        originY: 'top',
        transparentCorners:false
        
    }));
fabric.Object.prototype._drawControl =    function(control, ctx, methodName, left, top, styleOverride) {
      styleOverride = styleOverride || {};
      if (!this.isControlVisible(control)) {
        return;
      }
      var size = this.cornerSize, stroke = !this.transparentCorners && this.cornerStrokeColor;
      switch (styleOverride.cornerStyle || this.cornerStyle) {
        case 'circle':
        if(control == this.__corner){
          ctx.save();
         ctx.strokeStyle = ctx.fillStyle='red';
        }
          ctx.beginPath();
          ctx.arc(left + size / 2, top + size / 2, size / 2, 0, 2 * Math.PI, false);
          ctx[methodName]();
          if (stroke) {
            ctx.stroke();
          }
          if(control == this.__corner){
          ctx.restore();
         
        }
          break;
        default:
          this.transparentCorners || ctx.clearRect(left, top, size, size);
          ctx[methodName + 'Rect'](left, top, size, size);
          if (stroke) {
            ctx.strokeRect(left, top, size, size);
          }
      }
    } 

<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/3.2.0/fabric.js"></script>

<br/>
<canvas id="fabriccanvas" width="600" height="200" style="border:1px solid #ccc"></canvas>