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Martin Wendt edited this page Feb 10, 2019 · 29 revisions

About Fancytree drag-and-drop extension (HTML5 based).

Add Drag-and-Drop support:

  • Compatible with the HTML Drag and Drop API.
  • Drag nodes inside one tree, i.e. re-order, move, or copy.
  • Drag nodes between different trees (even on different iframes, windows, or pages).
  • Any element that has the draggable="true"attribute set may be dropped over a Fancytree node.
  • Drop a Fancytree node on any element that implements the HTML Drag and Drop API, including text editors or desktop items.
  • Requires IE 11 or later, or recent Chrome, Firefox, Safari.

Note: There is also another extension (ext-dnd) available that implements drag-and-drop support using the jQuery UI draggable and jQuery UI droppable API.
Unless you need to support those APIs, it is recommended to use ext-dnd5.

Usage

In addition to jQuery and Fancytree, include jquery.fancytree.dnd5.js:

  <script src="//code.jquery.com/jquery-3.3.1.min.js"></script>

  <link href="skin-win8/ui.fancytree.css" rel="stylesheet">
  <script src="js/jquery-ui-dependencies/jquery.fancytree.ui-deps.js"></script>
  <script src="js/jquery.fancytree.js"></script>
  <script src="js/jquery.fancytree.dnd5.js"></script>

Enable dnd5 extension and pass options:

$("#tree").fancytree({
  extensions: ["dnd5"],
  dnd5: {
    // Available options with their default:
    autoExpandMS: 1500,      // Expand nodes after n milliseconds of hovering.
    dropMarkerOffsetX: -24,  // absolute position offset for .fancytree-drop-marker
                             // relatively to ..fancytree-title (icon/img near a node accepting drop)
    dropMarkerInsertOffsetX: -16, // additional offset for drop-marker with hitMode = "before"/"after"
		multiSource: false,		        // true: Drag multiple (i.e. selected) nodes.
    preventForeignNodes: false,   // Prevent dropping nodes from different Fancytrees
    preventNonNodes: false,       // Prevent dropping items other than Fancytree nodes
    preventRecursiveMoves: true,  // Prevent dropping nodes on own descendants
    preventVoidMoves: true,       // Prevent dropping nodes 'before self', etc.
    scroll: true,                 // Enable auto-scrolling while dragging
    scrollSensitivity: 20,        // Active top/bottom margin in pixel
    scrollSpeed: 5,               // Pixel per event
    // Events (drag support)
    dragStart: null,       // Callback(sourceNode, data), return true, to enable dnd drag
    dragDrag: $.noop,      // Callback(sourceNode, data)
    dragEnd: $.noop,       // Callback(sourceNode, data)
    // Events (drop support)
    dragEnter: null,       // Callback(targetNode, data), return true, to enable dnd drop
    dragOver: $.noop,      // Callback(targetNode, data)
    dragExpand: $.noop,    // Callback(targetNode, data)
    dragDrop: $.noop,      // Callback(targetNode, data)
    dragLeave: $.noop      // Callback(targetNode, data)
  },
  [...]
});

All callback methods are passed a data object:

{
  node: {FancytreeNode},        // The node that the event refers to (also passed as first argument)
  tree: {Fancytree},            // The tree that the event refers to
  options: {object},            // Plugin options accessible as `options.dnd5`
  originalEvent: {Event},       // The original jQuery Event that caused this callback
  widget: {object},             // The jQuery UI tree widget
  otherNode: {FancytreeNode},   // If applicable: the other node, e.g. drop source, ...
  dataTransfer: {DataTransfer}, // Access drag data, drag iamge, and drop-effect
  dropEffect: {string},         // Set by dragend and drop ('move', 'copy', or 'link')
  hitMode: {string},            // 'over', 'after', 'before'
  isCancelled: {boolean},       // Set by dragend and drop
}

Example

$("#tree").fancytree({
  extensions: ["dnd5"],

  // .. other options...

  dnd5: {
    autoExpandMS: 1500,
    preventRecursiveMoves: true, // Prevent dropping nodes on own descendants
    preventVoidMoves: true, // Prevent dropping nodes 'before self', etc.

    // --- Drag Support --------------------------------------------------------

    dragStart: function(node, data) {
      // Called when user starts dragging `node`.
      // This method MUST be defined to enable dragging for tree nodes.
      //
      // We can
      //   Add or modify the drag data using `data.dataTransfer.setData()`
      //   Return false to cancel dragging of `node`.

      // For example:
//    if( data.originalEvent.shiftKey ) ...          
//    if( node.isFolder() ) { return false; }
      return true;
    },
    dragDrag: function(node, data) {
      // Called every few microseconds while `node` is dragged.
      // Implementation of this callback is optional and rarely required.
    },
    dragEnd: function(node, data) {
      // Called when the drag operation has terminated.
      // Check `data.isCancelled` to see if a drop occurred.
      // Implementation of this callback is optional and rarely required.
    },

    // --- Drop Support --------------------------------------------------------

    dragEnter: function(node, data) {
      // Called when s.th. is dragged over `node`.
      // `data.otherNode` may be null for non-fancytree droppables.
      //
      // We may
      //   Set `data.dataTransfer.effectAllowed` and `.dropEffect`
      //   Call `data.dataTransfer.setDragImage()`
      //
      // Return
      //   - false to prevent dropping (dragOver and dragLeave are not called)
      //   - a list (e.g. ["before", "after"]) to restrict available hitModes
      //   - "over", "before, or "after" to force a hitMode
      //   - Any other return value will calc the hitMode from the cursor position.

      // Example:
      // Prevent dropping a parent below another parent (only sort nodes under
      // the same parent):
//    if(node.parent !== data.otherNode.parent){
//      return false;
//    }
      // Example:
      // Don't allow dropping *over* a node (which would create a child). Just
      // allow changing the order:
//    return ["before", "after"];
      // Accept everything:
      return true;
    },
    dragOver: function(node, data) {
      // Called every while s.th. is dragged over `node`.
      // `data.hitMode` contains the calculated insertion point, based on cursor
      // position and the response of `dragEnter`.
      //
      // We may
      //   Override `data.hitMode`
      //   Set `data.dataTransfer.effectAllowed` and `.dropEffect`
      //   Call `data.dataTransfer.setDragImage()`
    },
    dragExpand: function(node, data) {
      // Called when a dragging cursor lingers over a parent node.
      // (Optional) Return false to prevent auto-expanding `node`.
    },
    dragLeave: function(node, data) {
      // Called when s.th. is no longer dragged over `node`.
      // Implementation of this callback is optional and rarely required.
    },
    dragDrop: function(node, data) {
      // This function MUST be defined to enable dropping of items on the tree.
      //
      // The source data is provided in several formats:
      //   `data.otherNode` (null if it's not a FancytreeNode from the same page)
      //   `data.otherNodeData` (Json object; null if it's not a FancytreeNode)
      //   `data.dataTransfer.getData()`
      //
      // We may access some meta data to decide what to do:
      //   `data.hitMode` ("before", "after", or "over").
      //   `data.dataTransfer.dropEffect`,`.effectAllowed`
      //   `data.originalEvent.shiftKey`, ...
      //
      // Example:

      var transfer = data.dataTransfer;

      node.debug("drop", data);

      if( data.otherNode ) {
        // Drop another Fancytree node from same frame
        // (maybe from another tree however)
        var sameTree = (data.otherNode.tree === data.tree);

        data.otherNode.moveTo(node, data.hitMode);
      } else if( data.otherNodeData ) {
        // Drop Fancytree node from different frame or window, so we only have
        // JSON representation available
        node.addChild(data.otherNodeData, data.hitMode);
      } else {
        // Drop a non-node
        node.addNode({
          title: transfer.getData("text")
        }, data.hitMode);
      }
      // Expand target node when a child was created:
      node.setExpanded();
    }
  }
});

Status Classes

By default, some classes are added to the nodes, to enable visual feedback:

  • TODO

Recipes

[Howto] Copy a node on drop

This is accomplished by the node.copyTo() method.
When a node is copied from the same tree, we should define a new key, or let the tree generate one:

  dragDrop: function(node, data) {
    newNode = data.otherNode.copyTo(node, data.hitMode, function(n){
      n.title = "Copy of " + n.title;
      n.key = null; // make sure, a new key is generated
    });
  }

[Howto] Control scrolling inside the tree container while dragging

The auto scroll feature is on by default. It works by scrolling the whole tree when the drag cursor is near the upper or lower margin of the scroll parent:

scroll: true,
scrollSpeed: 7,
scrollSensitivity: 10,

The container may also be set to a fixed sized by a custom rule, to enable scrolling inside the tree-container only:

ul.fancytree-container {
    height: 200px;
    overflow-y: auto;
}

[Howto] Drop on a lazy node

Dropping a node onto a lazy folder may not work as expected: The item that is dragged will appear in that folder but it stops the node from performing the Ajax request.
This is 'works as designed': lazy folders only generate an Ajax request if the children property is null or undefined (in order to prevent lazy-loading a second time).

We could however expand the node before adding the dropped node:

dragDrop: function(node, data) {
  node.setExpanded(true).always(function(){
    // Wait until expand finished, then add the additional child
    data.otherNode.moveTo(node, data.hitMode);
  });
}

(Another pattern could be: issue an Ajax request to notify the server about the new node. Then reload the branch.)

[Howto] Accept non-nodes as drop source

We can drop any element onto Fancytree, that satisfies the HTML Drag and Drop API, for example:

<span class="drag-source" draggable="true"
  ondragstart="event.dataTransfer.setData('text/plain', 'Drag me');">
  Drag me</span>

Also other elements may generate drop-events by default:

  • <input> elements and <a> tags
  • selected text from a text editor
  • Files from your computer's desktop, ...
$("#tree").fancytree({
  extensions: ["dnd5"],
  ...
  dnd5: {
    preventNonNodes: false,      // Allow dropping items other than Fancytree nodes
    ...
    dragEnter: function(node, data) {
      //
      return true;
    },
    dragDrop: function(node, data) {
      if( !data.otherNode ){
        // It's a non-tree draggable
        alert("dropped " + $(data.draggable.element).text());
        return;
      }
      data.otherNode.moveTo(node, data.hitMode);
        /* This function MUST be defined to enable dropping of items on
         * the tree.
         */
        var transfer = data.dataTransfer;

        node.debug("drop", data);
        if( data.otherNode ) {
          // Drop another Fancytree node from same frame
          // (maybe from another tree however)
          var sameTree = (data.otherNode.tree === data.tree);

          data.otherNode.moveTo(node, data.hitMode);

        } else if( data.otherNodeData ) {
          // Drop Fancytree node from different frame
          node.addChild(data.otherNodeData, data.hitMode);

        } else {
          // Drop a non-node
          transfer.effect = "copy";
          node.addNode({
            title: transfer.getData("text/plain")
          }, data.hitMode);
        }
        node.setExpanded();
      }
    }
  }
});

Note: ext-dnd5 does not make use of the jQuery UI draggable API.

[Howto] Accept Fancytree nodes as source for a standard droppable

We can drop a Fancytree node on any target, that implements the HTML Drag and Drop API.

For example these elements are potential drop targets:

  • Another Fancytree widget on the same page or another browser window
  • <input> and <textarea> elements
  • Text editor windows
  • File Explorer, your computer's desktop, ...

Note: ext-dnd5 does not make use of the jQuery UI droppable API.

Notes: See also [Howto] Control scrolling inside the tree container while dragging

[Howto] Modify the drag icon

$("#tree").fancytree({
  dnd5: {
    ... TODO
  }
  [...]
});

[Howto] Implement copy/move modifier keys

There is no built-in 'useModifiers' option, because the potential use cases are too diverse. But we can implement the desired behavior using callbacks.

See the example

[Howto] Implement multi-node drag'n'drop

There is no built-in 'multiDnd' option, because the potential use cases are too diverse. But we can implement the desired behavior using callbacks.

See the example

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