A mixin which adds default drag and drop support for CZML files to the Viewer widget.
Rather than being called directly, this function is normally passed as
a parameter to Viewer#extend, as shown in the example below.
    
    
    
	
	
    
    
    
        Parameters:
        
    
	
		
		| Name | Type | Argument | Description | 
	
	
	
	
	
        
            
                | viewer | Viewer |  | The viewer instance. | 
	
	
	
        
            
                | options | Object | <optional> 
 | Configuration options for the mixin. Properties
    
	
		
		| Name | Type | Argument | Default | Description |  
            
                | dropTarget | Element
                         | 
                    
                        String | <optional> 
 | viewer.container | The DOM element which will serve as the drop target. |  
            
                | clearOnDrop | Boolean | <optional> 
 | true | When true, dropping files will clear all existing data sources first, when false, new data sources will be loaded after the existing ones. |  | 
	
	
	
    
    
    
    
    
    Throws:
    
    
     
    
    
        Example
        
    // Add basic drag and drop support and pop up an alert window on error.
var viewer = new Cesium.Viewer('cesiumContainer');
viewer.extend(Cesium.viewerDragDropMixin);
viewer.dropError.addEventListener(function(viewerArg, source, error) {
    window.alert('Error processing ' + source + ':' + error);
});
    
	
	
    
        
	
	
	
	
	
	
	
	
	
	
	
	
	
	
    
	
     
	
	
	
	
	Source: