Advanced

Advanced Drag-and-Drop

Here we speak about advanced drag-n-drop options and find solutions how to make any elements on the page draggable and control each stage of DnD.

For simple dragging and dropping of items within one and the same component as well as between different views and their instances - study the article about built-in Webix DnD options.

DnD syntax

If you want to make some element on page draggable you can use

webix.DragControl.addDrag(node);

where node - id or HTML node object ( or object itself )

Related sample:  Drag-and-Drop from HTML

If you want to define some area as drop target you can use

webix.DragControl.addDrop(node);

where node - id or HTML node object ( or object itself ).

Controlled DnD

If you want to control different aspects of the drag-n-drop process, you can use the above methods but with an extra control parameter ($drag or $drop) with a custom function:

//for dragging
webix.DragControl.addDrag(node, $drag:function(source, target, event){...});
//for dropping
webix.DragControl.addDrop(node, $drop:function(source, target, event){...});

The control function takes three parameters:

  • source - source HTML object;
  • target - target HTML object;
  • event - native event.

This is how you can set value of an input by drag-n-drop:

webix.DragControl.addDrop("mytext", {
    $drop:function(source, target, event){
        var dnd = webix.DragControl.getContext();
        target.value = dnd.from.getItem(dnd.source[0]).title; // setting source item title as input value
    }
});

Related sample:  Drag-and-Drop to HTML

DnD context

Context object of drag-n-drop can be accessed as:

var state = webix.DragControl.getContext();

It is also available as parameter in all drag-n-drop related events:

state = {
    source:[1,2,3], //array of IDs for dragged elements
    target:id, //ID of currently active target item
    from:some_obj, // reference to the source object
    to:some_obj, // reference to the target object
    html:text //optional, custom text, which is rendered as drag-item
}

Set of the drag control methods

There are several DnD control methods: some of them are used for dragged element (addDrag) and others - for drop target (addDrop). All these events can be used to define a custom behavior for elements included in the current drag-n-drop:

addDrag()-related events:

  • $drag - is called when an element is dragged;
  • $dragCreate - is called at the moment when drag has been created;
  • $dragDestroy - is called when drag has been completed.

addDrop() related events:

  • $dragIn - is called when the dragged element enters the drop area;
  • $dragOut - is called when the dragged element leaves the drop area;
  • $drop - fires when you drop the dragged element.
{
  $dragIn:function(source, target, event){ ... },   //drag moves in potential drop area
  $dragOut:function(source, target, event){ ... },  //drag moves out from the drop area
  $drop:function(source, target, event){ ... },     //drag was released
  $drag:function(source, target, event){ ... },     //drag is started
  $dragCreate:function(from, event){ ... }     //dnd is started
  $dragDestroy:function:(from, text){ ... } //dnd is finished
}

Where:

  • source - source HTML object;
  • target - target HTML object;
  • event - native event;
  • from - control object related to source of dnd;
  • text - content of drag marker.

If any of onDrag handlers are redefined, there won't be the default processing of the action. The code expects that your custom handler will do all the job.

DnD masters

Master is a component object or a hash code of the control methods. It specifies how element will behave itself in the drop target.

If you specify the master, it will be responsible for the appropriate drag-n-drop behavior. If you don't do it, the standard drag-n-drop processing will occur.

For the methods, where source and target masters are not provided, you can get them by the getMaster method:

var source_master = webix.DragControl.getMaster(source);
var target_master = webix.DragControl.getMaster(target);

Interface-based DnD

You can make an element draggable by adding one of the 2 appropriate interfaces:

Low level interface. A component which inherits it can be moved by drag-n-drop (to learn how to inherit the interface, read the Component Copying and Extending article).

High level interface. Adds drag-n-drop ability to component which uses DataStore (to learn how to inherit the interface, read the Component Copying and Extending article).

Samples of usage

Drag from custom HTML

<div package="DragPackage" version="1.0" maintainer="Webix Team" 
    id="drag_1" 
    style='width:150px; height:50px; color:white; background-color:navy;'>
    Drag me into the dataview
</div>
webix.DragControl.addDrag("drag_1");
data1.attachEvent("onBeforeDrop",function(context){
    if (context.from == webix.DragControl){
        this.add({
            Package:context.source.getAttribute("package"),
            Version:context.source.getAttribute("version"),
            Maintainer:context.source.getAttribute("maintainer")
        }), this.getIndexById(context.target || this.getFirstId());
        return false;
    }
    return true;
});

Drag to custom HTML

<div id="data_container2" style="width:400px;height:396px;border:1px solid red;">
    Drop some item here
</div>
webix.DragControl.addDrop("data_container2",{
    $drop:function(source, target, e){
        var context = webix.DragControl.getContext();
        var item = context.from.getItem(context.source[0]);
 
        var d = document.createElement("DIV");
        d.innerHTML = item.Package+" - "+item.Version;
        target.appendChild(d);
    }
});
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