Drag & Drop with snap Option


Advertisements


Description

This option is used to cause a draggable to snap to a grid or to constrain its movement.

  • If it is set to false (default), no snapping or constraining occurs.

  • If an integer x, the draggable will snap to a grid of x pixels.

  • If an array [x, y], the horizontal dragging will snap to a grid of x pixels and the vertical will snap to y pixels.

  • It can also be a function conforming to Function( x , y , draggable ) that returns an array [x, y].

Syntax

Here are various syntaxes to use the snap option.

// Snap target to a 50-pixel grid while dragging
new Draggable('element', {snap:50});

OR

// Constrain dragging to a 100x50px box
new Draggable('element', {
   snap: function(x, y) {
      return[ (x < 100) ? (x > 0 ? x : 0 ) : 100, (y < 50) ? (y > 0 ? y : 0) : 50 ];
   }
});

OR

// Constrain dragging to element's parent node
new Draggable('element', {
   snap: function(x, y, draggable) {
      function constrain(n, lower, upper) {
		
         if (n > upper) 
            return upper;
         else if (n < lower) 
            return lower;
         else 
            return n;
      }
		
      var element = draggable.element.getDimensions( );
      var parent = draggable.element.parentNode.getDimensions( );
      return [
         constrain(x, 0, parent.width - element.width),
         constrain(y, 0, parent.height - element.height)
      ];
   }
});

Example

<html>
   <head>
      <title>Draggables Elements</title>
		
      <script type="text/javascript" src="/javascript/prototype.js"></script>
      <script type="text/javascript" src="/javascript/scriptaculous.js"></script>
		
      <script type="text/javascript">

         window.onload = function() {
            new Draggable('myimage', 
               {
               revert:true, snap: function(x, y) {
                  return[ (x < 100) ? (x > 0 ? x : 0 ) : 100, (y < 50) ? (y > 0 ? y : 0) : 50 ];
                  }
               } 
            );
         }
      </script>
		
   </head>
   <body>
	
      <p>Try to drag the following image out of its defined
         boundary and see the result. Later change its boundary and
         repeat the exercise.</p>

      <img id="myimage" src="/images/scriptaculous.gif"/>
   </body>
</html>

This will produce following result −


scriptaculous_drag_drop.htm

Advertisements