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// Copyright 2010 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Provides a files drag and drop event detector. It works on
* HTML5 browsers.
*
* @see ../demos/filedrophandler.html
*/
goog.provide('goog.events.FileDropHandler');
goog.provide('goog.events.FileDropHandler.EventType');
goog.require('goog.array');
goog.require('goog.debug.Logger');
goog.require('goog.dom');
goog.require('goog.events');
goog.require('goog.events.BrowserEvent');
goog.require('goog.events.EventHandler');
goog.require('goog.events.EventTarget');
goog.require('goog.events.EventType');
/**
* A files drag and drop event detector. Gets an {@code element} as parameter
* and fires {@code goog.events.FileDropHandler.EventType.DROP} event when files
* are dropped in the {@code element}.
*
* @param {Element|Document} element The element or document to listen on.
* @param {boolean=} opt_preventDropOutside Whether to prevent a drop on the
* area outside the {@code element}. Default false.
* @constructor
* @extends {goog.events.EventTarget}
*/
goog.events.FileDropHandler = function(element, opt_preventDropOutside) {
goog.events.EventTarget.call(this);
/**
* Handler for drag/drop events.
* @type {!goog.events.EventHandler}
* @private
*/
this.eventHandler_ = new goog.events.EventHandler(this);
var doc = element;
if (opt_preventDropOutside) {
doc = goog.dom.getOwnerDocument(element);
}
// Add dragenter listener to the owner document of the element.
this.eventHandler_.listen(doc,
goog.events.EventType.DRAGENTER,
this.onDocDragEnter_);
// Add dragover listener to the owner document of the element only if the
// document is not the element itself.
if (doc != element) {
this.eventHandler_.listen(doc,
goog.events.EventType.DRAGOVER,
this.onDocDragOver_);
}
// Add dragover and drop listeners to the element.
this.eventHandler_.listen(element,
goog.events.EventType.DRAGOVER,
this.onElemDragOver_);
this.eventHandler_.listen(element,
goog.events.EventType.DROP,
this.onElemDrop_);
};
goog.inherits(goog.events.FileDropHandler, goog.events.EventTarget);
/**
* Whether the drag event contains files. It is initialized only in the
* dragenter event. It is used in all the drag events to prevent default actions
* only if the drag contains files. Preventing default actions is necessary to
* go from dragenter to dragover and from dragover to drop. However we do not
* always want to prevent default actions, e.g. when the user drags text or
* links on a text area we should not prevent the browser default action that
* inserts the text in the text area. It is also necessary to stop propagation
* when handling drag events on the element to prevent them from propagating
* to the document.
* @private
* @type {boolean}
*/
goog.events.FileDropHandler.prototype.dndContainsFiles_ = false;
/**
* A logger, used to help us debug the algorithm.
* @type {goog.debug.Logger}
* @private
*/
goog.events.FileDropHandler.prototype.logger_ =
goog.debug.Logger.getLogger('goog.events.FileDropHandler');
/**
* The types of events fired by this class.
* @enum {string}
*/
goog.events.FileDropHandler.EventType = {
DROP: goog.events.EventType.DROP
};
/** @override */
goog.events.FileDropHandler.prototype.disposeInternal = function() {
goog.events.FileDropHandler.superClass_.disposeInternal.call(this);
this.eventHandler_.dispose();
};
/**
* Dispatches the DROP event.
* @param {goog.events.BrowserEvent} e The underlying browser event.
* @private
*/
goog.events.FileDropHandler.prototype.dispatch_ = function(e) {
this.logger_.fine('Firing DROP event...');
var event = new goog.events.BrowserEvent(e.getBrowserEvent());
event.type = goog.events.FileDropHandler.EventType.DROP;
this.dispatchEvent(event);
};
/**
* Handles dragenter on the document.
* @param {goog.events.BrowserEvent} e The dragenter event.
* @private
*/
goog.events.FileDropHandler.prototype.onDocDragEnter_ = function(e) {
this.logger_.finer('"' + e.target.id + '" (' + e.target + ') dispatched: ' +
e.type);
var dt = e.getBrowserEvent().dataTransfer;
// Check whether the drag event contains files.
this.dndContainsFiles_ = !!(dt &&
((dt.types &&
(goog.array.contains(dt.types, 'Files') ||
goog.array.contains(dt.types, 'public.file-url'))) ||
(dt.files && dt.files.length > 0)));
// If it does
if (this.dndContainsFiles_) {
// Prevent default actions.
e.preventDefault();
}
this.logger_.finer('dndContainsFiles_: ' + this.dndContainsFiles_);
};
/**
* Handles dragging something over the document.
* @param {goog.events.BrowserEvent} e The dragover event.
* @private
*/
goog.events.FileDropHandler.prototype.onDocDragOver_ = function(e) {
this.logger_.finest('"' + e.target.id + '" (' + e.target + ') dispatched: ' +
e.type);
if (this.dndContainsFiles_) {
// Prevent default actions.
e.preventDefault();
// Disable the drop on the document outside the drop zone.
var dt = e.getBrowserEvent().dataTransfer;
dt.dropEffect = 'none';
}
};
/**
* Handles dragging something over the element (drop zone).
* @param {goog.events.BrowserEvent} e The dragover event.
* @private
*/
goog.events.FileDropHandler.prototype.onElemDragOver_ = function(e) {
this.logger_.finest('"' + e.target.id + '" (' + e.target + ') dispatched: ' +
e.type);
if (this.dndContainsFiles_) {
// Prevent default actions and stop the event from propagating further to
// the document. Both lines are needed! (See comment above).
e.preventDefault();
e.stopPropagation();
// Allow the drop on the drop zone.
var dt = e.getBrowserEvent().dataTransfer;
dt.effectAllowed = 'all';
dt.dropEffect = 'copy';
}
};
/**
* Handles dropping something onto the element (drop zone).
* @param {goog.events.BrowserEvent} e The drop event.
* @private
*/
goog.events.FileDropHandler.prototype.onElemDrop_ = function(e) {
this.logger_.finer('"' + e.target.id + '" (' + e.target + ') dispatched: ' +
e.type);
// If the drag and drop event contains files.
if (this.dndContainsFiles_) {
// Prevent default actions and stop the event from propagating further to
// the document. Both lines are needed! (See comment above).
e.preventDefault();
e.stopPropagation();
// Dispatch DROP event.
this.dispatch_(e);
}
};
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