jquery resizable 1px mismatch error

Question

I am trying to use jquery resizable handlers with absolute position square divs

but when I click the "north" and "west" button(only this two direction) and drag just a little for resizing, the box itself became smaller by 1 or 2px

in north handler case, like (top:100px,height:100px => top:99px,height:99px)

what did I do wrong??

element.resizable({
    minWidth: 1,
    minHeight: 1,
    handles:{
        'n': '.ui-resizable-n',
        'w': '.ui-resizable-w',
        'e': '.ui-resizable-e',
        's': '.ui-resizable-s'
    }
})

Here's a demo link!

when I drag "keeper" item to "screen" and move north resize handler little, the square makes problem

Answer 1

Please change box-sizing: border-box; to box-sizing: content-box;.

https://jsfiddle.net/6h02cmvf/

$(document).ready(function() {
		$('#container > .ui-element-libraries-container > .ui-element-container').draggable({
			opacity: 0.5,
			helper: "clone",
			appendTo: '#full',
			cursor: "move",
			revert: true
		})

		$('#screen').droppable({
			drop: (event,ui)=>{
				let layoutOffset=$('#screen').offset()
				let element=ui.helper.clone().css({
					'position': 'absolute',
					'opacity': 1,
					'left': (ui.position.left-layoutOffset.left)+'px',
					'top': (ui.position.top-layoutOffset.top)+'px',
				})
				element.toggleClass('ui-element-container ui-element')
				element.empty()
				element.append("<div class='ui-resizable-handle ui-resizable-n'></div>")
				element.append("<div class='ui-resizable-handle ui-resizable-s'></div>")
				element.append("<div class='ui-resizable-handle ui-resizable-e'></div>")
				element.append("<div class='ui-resizable-handle ui-resizable-w'></div>")
				element.appendTo('#screen')
				element.resizable({
					minWidth: 1,
					minHeight: 1,
					handles:{
						'n': '.ui-resizable-n',
						'w': '.ui-resizable-w',
						'e': '.ui-resizable-e',
						's': '.ui-resizable-s'
					}
				})
				ui.helper.remove()
			}
		})
	})

.pane{
  color: black;
  background-color: white;
  position: absolute;
  display: block;
  overflow: hidden;
  border: 2px solid black;
}
#container{
  margin: 0px;
  left: 300px;
  right: auto;
  top: 0px;
  bottom: 0px;
  width: 300px;
  height: 500px;
}
#screen{
  margin: 0px;
  left: 0px;
  right: auto;
  top: 0px;
  bottom: 0px;
  width: 300px;
  height: 500px;
}
.ui-element-libraries-container{
  width:100%;
}
.ui-element-container{
  color: black;
  background-color: yellow;
  border: 1px solid black;
  margin-left: -1px;
  margin-top: -1px;
  width: 33.3%;
  min-width: 80px;
  max-width: 90px;
  height: 100px;
  box-sizing: border-box;
  text-align: center;
  line-height: 12px;
  float:left;
  font-size: 11px;
  position: relative;
  overflow: hidden;
  cursor: move;				
}
.ui-element{
  color: black;
  background-color: white;
  border: 1px solid black;
  margin-left: -1px;
  margin-top: -1px;
  width: 100px;
  height: 100px;
  box-sizing: content-box;
  text-align: center;
  line-height: 12px;
  float:left;
  font-size: 11px;
  position: relative;
  cursor: move;	
}
.ui-resizable-handle{
  position: absolute;
  width: 7px;
  height: 7px;
  border: 1px solid blue;
  background: white;
  display: block;
}
.ui-resizable-n{
  top: -4px;
  bottom: auto;
  left: 50%;
  right: auto;
  margin-left: -4px;
  cursor: ns-resize;		
}
.ui-resizable-s{
  top: auto;
  bottom: -4px;
  left: 50%;
  right: auto;
  margin-left: -4px;
  cursor: ns-resize;		
}
.ui-resizable-e{
  top: 50%;
  bottom: auto;
  left: auto;
  right: -4px;
  margin-top: -4px;
  cursor: ew-resize;
}
.ui-resizable-w{
  top: 50%;
  bottom: auto;
  left: -4px;
  right: auto;
  margin-top: -4px;
  cursor: ew-resize;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.10.4/jquery-ui.min.js"></script>

<div id="full">
  <div id="screen" class="pane">
    screen
  </div>
  <div id="container" class="pane">
    keeper
    <div class="ui-element-libraries-container">
      <div class="ui-element-container">
        <div>
          b
        </div>
      </div>
    </div>
  </div>
</div>