Add Delete button on element in Canvas Fabric JS

Question

Hi I want to add delete button in element using FabricJS. I Have an example:

I try adding this part of code but when I resize image the delete button don't stay on place.

http://jsfiddle.net/wxao1on8/13/

   function addDeleteBtn(x, y, w){
        $(".deleteBtn").remove();
        var btnLeft = x;
        var btnTop = y - 30;
        var widthadjust=w/2;
        btnLeft=widthadjust+btnLeft-1
        var deleteBtn = '<img src="https://www.funagain.com/images/old/common/delete-icon.png" class="deleteBtn" ' +
                'style="position:absolute;top:'+btnTop+'px;right:'+btnLeft+'px;cursor:pointer;"/>';
        $(".canvas-container").append(deleteBtn);
    }

    canvas.on('object:selected',function(e){
        addDeleteBtn(e.target.oCoords.mt.x, e.target.oCoords.mt.y, e.target.width);
    });

    canvas.on('mouse:down',function(e){
        if(!canvas.getActiveObject())
        {
            $(".deleteBtn").remove();
        }
    });

    canvas.on('object:modified',function(e){
        addDeleteBtn(e.target.oCoords.mt.x, e.target.oCoords.mt.y, e.target.width);
    });

    canvas.on('object:moving',function(e){
        $(".deleteBtn").remove();
    });

    $(document).on('click',".deleteBtn",function(){
        if(canvas.getActiveObject())
        {
            canvas.remove(canvas.getActiveObject());
            $(".deleteBtn").remove();
        }
    });

Answer 1

target.oCoords.mt is middle-top corner.

Use the top-right corner instead: e.target.oCoords.tr

    var canvas = new fabric.Canvas('canvas');
var HideControls = {
            'tl':true,
            'tr':false,
            'bl':true,
            'br':true,
            'ml':true,
            'mt':true,
            'mr':true,
            'mb':true,
            'mtr':true
        };
fabric.Image.fromURL('http://serio.piiym.net/CVBla/txtboard/thumb/1260285874089s.jpg', function (img) {
    img.top = 60;
    img.left = 30;
    img.setControlsVisibility(HideControls);
    canvas.add(img);
});

canvas.renderAll();

function addDeleteBtn(x, y){
    $(".deleteBtn").remove(); 
    var btnLeft = x-10;
    var btnTop = y-10;
    var deleteBtn = '<img src="https://www.funagain.com/images/old/common/delete-icon.png" class="deleteBtn" style="position:absolute;top:'+btnTop+'px;left:'+btnLeft+'px;cursor:pointer;width:20px;height:20px;"/>';
    $(".canvas-container").append(deleteBtn);
}

canvas.on('object:selected',function(e){
        addDeleteBtn(e.target.oCoords.tr.x, e.target.oCoords.tr.y);
});

canvas.on('mouse:down',function(e){
    if(!canvas.getActiveObject())
    {
        $(".deleteBtn").remove(); 
    }
});

canvas.on('object:modified',function(e){
    addDeleteBtn(e.target.oCoords.tr.x, e.target.oCoords.tr.y);
});

canvas.on('object:scaling',function(e){
    $(".deleteBtn").remove(); 
});
canvas.on('object:moving',function(e){
    $(".deleteBtn").remove(); 
});
canvas.on('object:rotating',function(e){
    $(".deleteBtn").remove(); 
});
$(document).on('click',".deleteBtn",function(){
    if(canvas.getActiveObject())
    {
        canvas.remove(canvas.getActiveObject());
        $(".deleteBtn").remove();
    }
});

Answer 2

Hello i would suggest a different approach to this functionality that it is more stable as it does not add elements on the DOM , we can use it on as many objects as we like , we dont need to hide and show the custom corner buttons, and the corner buttons are visible each time the object is active(native fabricjs functions).

1. I am going to override the object's prototype _drawControl function , for to add my custom corner images.
2. And override the canvas prototype _setCornerCursor , for to change realtime the mouse cursor ,according to which corner is over.
3. I have made a live fiddle here : https://jsfiddle.net/tornado1979/j987gb6f/

A. First of all i need to preload the custom corner images, so whenever we click on an object there would not be any delay(i used random images just for the show).

var ctrlImages = new Array()

  function preload() {
    for (i = 0; i < preload.arguments.length; i++) {
      ctrlImages[i] = new Image();
      ctrlImages[i].src = preload.arguments[i];
    }
  }

  preload(
      "https://cdn1.iconfinder.com/data/icons/ui-color/512/Untitled-12-128.png",
      "https://cdn2.iconfinder.com/data/icons/social-messaging-productivity-1/128/sync-16.png",
      "https://cdn2.iconfinder.com/data/icons/social-messaging-productivity-1/128/write-compose-16.png",

B. I override the _drawcontrol (i show just the snippet that change the corners):

switch (control)
            {
            case 'tl':
              SelectedIconImage.src = ctrlImages[1].src;//our custom img
              break;
            case 'tr':
              if (flipiX && !flipiY) { n='2'; }
              if (!flipiX && flipiY) { n='3'; }
              if (flipiX && flipiY) { n='4'; }
              SelectedIconImage.src = ctrlImages[0].src;//our custom img
              break;
            case 'mt':

              break;
            case 'bl':
              if (flipiY) { n='2'; }
             SelectedIconImage.src = ctrlImages[3].src;//our custom img
              break;
            case 'br':
              if (flipiX || flipiY) { n='2'; }
              if (flipiX && flipiY) { n=''; }
              SelectedIconImage.src = ctrlImages[2].src;//our custom img
              break;
            case 'mb':

              break;
            case 'ml':

              break;
            case 'mr':

              break;
            default:
              ctx[methodName](left, top, sizeX, sizeY);
              break;
            }

C. Override _setCornerCursor function, for to change the cursor when mouse is over object's corner. Inside the function i use the setCursor() function which actually takes a string as a parameter, so we can take a look here for cursors: https://www.w3.org/TR/css3-ui/#cursor

fabric.Canvas.prototype._setCornerCursor =  function(corner, target) {
      //for top left corner
       if(corner == "tl"){
          this.setCursor(this.rotationCursor); return false;
          //for top right corner
      }else if(corner == "tr"){
          this.setCursor('pointer'); return false;
          //for bottom left corner
      }else if(corner == "bl"){
          this.setCursor('help'); return false;      
          //for bottom right corner
      }else if(corner == "br"){
          this.setCursor('copy'); return false;      
      }
    };

D. And finaly on mouse:down i check the corner and add functionality canvas.on('mouse:down',function(e){..}

Hope helps, good luck.