flutter_flutter/framework/sky-element/sky-element.sky

<!--
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
-->
<import src="sky-binder.sky" as="binder" />
<script>
var attributeConverters = {
  boolean: function(value) {
    if (typeof value == 'string')
      return value == 'true';
    return !!value;
  },
  number: function(value) {
    return Number(value);
  },
  string: function(value) {
    if (value === null)
      return '';
    return String(value);
  },
};

function parseAttributeSpec(spec) {
  var attributes = new Map();
  var attributeTokens = (spec || '').split(',');

  for (var i = 0; i < attributeTokens.length; ++i) {
    var parts = attributeTokens[i].split(':');
    var name = parts[0].trim();
    var type = (parts[1] || '').trim();
    var converter = attributeConverters[type] || attributeConverters.string;

    attributes.set(name, converter);
  }

  return attributes;
}

function collectEventHandlers(definition) {
  var eventHandlers = [];
  var attributes = definition.getAttributes();

  for (var i = 0; i < attributes.length; i++) {
    var attr = attributes[i];
    var name = attr.name;
    var value = attr.value;

    if (name.startsWith('on-')) {
      eventHandlers.push(name.substring(3));
    }
  }

  return eventHandlers;
}

function eventHandlerCallback(event) {
  var element = event.currentTarget;
  var registration = registrations.get(element.localName);
  var method = registration.getEventHandler(event.type);
  var handler = element[method];
  if (handler instanceof Function)
    return handler.call(element, event);
}

class ElementRegistration {
  constructor(definition) {
    this.definition = definition;
    this.tagName = definition.getAttribute('name');
    this.attributes = parseAttributeSpec(definition.getAttribute('attributes'));
    this.eventHandlers = collectEventHandlers(definition);
    this.template = definition.querySelector('template');
    Object.preventExtensions(this);
  }

  getEventHandler(eventName) {
    return this.definition.getAttribute('on-' + eventName);
  }

  getAttributeNames() {
    // TODO(esprehn): We can replace this method with
    // Array.from(registration.attributes) once we turn that on.
    var names = []
    this.attributes.forEach(function(converter, name) {
      names.push(name);
    });
    return names;
  }

  synthesizeAttributes(prototype) {
    this.attributes.forEach(function(converter, name) {
      Object.defineProperty(prototype, name, {
        get: function() {
          return converter(this.getAttribute(name));
        },
        set: function(newValue) {
          this.setAttribute(name, converter(newValue));
        },
        enumerable: true,
        configurable: true,
      });
    });
  }
}

var registrations = new Map();

class SkyElement extends HTMLElement {

  static register() {
    var definition = document.currentScript.parentNode;

    if (definition.localName !== 'sky-element') {
      throw new Error('register() calls must be inside a <sky-element>.');
    }

    var registration = new ElementRegistration(definition);

    if (!registration.tagName) {
      throw new Error('<sky-element> must have a name.');
    }

    if (registrations.has(registration.tagName)) {
      throw new Error('Duplicate registration for tag name: ' +
          registration.tagName);
    }

    registration.synthesizeAttributes(this.prototype);

    // TODO(esprehn): Combine the two element registries here and in sky binder.
    binder.registerElement(registration.tagName, {
      attributeNames: registration.getAttributeNames(),
    });

    registrations.set(registration.tagName, registration);
    return document.registerElement(registration.tagName, {
      prototype: this.prototype,
    });
  }

  created() {
    // override
  }

  attached() {
    // override
  }

  detached() {
    // override
  }

  attributeChanged(attrName, oldValue, newValue) {
    // override
  }

  shadowRootReady() {
    // override
  }

  createdCallback() {
    this.isAttached = false;
    this.created();

    Object.preventExtensions(this);

    // Invoke attributeChanged callback when element is first created too.
    var attributes = this.getAttributes();
    for (var i = 0; i < attributes.length; ++i) {
      var attribute = attributes[i];
      this.attributeChangedCallback(attribute.name, null, attribute.value);
    }

    var registration = registrations.get(this.localName);
    for (var i = 0; i < registration.eventHandlers.length; ++i) {
      var eventName = registration.eventHandlers[i];
      this.addEventListener(eventName, eventHandlerCallback);
    }
  }

  attachedCallback() {
    if (!this.shadowRoot) {
      var registration = registrations.get(this.localName);
      if (registration.template) {
        var shadow = this.ensureShadowRoot();
        var instance = binder.createInstance(registration.template, this);
        shadow.appendChild(instance.fragment);
        this.shadowRootReady();
      }
    }
    this.attached();
    this.isAttached = true;
  }

  detachedCallback() {
    this.detached();
    this.isAttached = false;
  }

  attributeChangedCallback(name, oldValue, newValue) {
    this.attributeChanged(name, oldValue, newValue);
    var registration = registrations.get(this.localName);
    var converter = registration.attributes.get(name);
    if (converter) {
      this.notifyPropertyChanged(name, converter(oldValue),
          converter(newValue));
    }
  }

  notifyPropertyChanged(name, oldValue, newValue) {
    var notifier = Object.getNotifier(this);
    notifier.notify({
      type: 'update',
      name: name,
      oldValue: oldValue,
    });
    var handler = this[name + 'Changed'];
    if (typeof handler == 'function')
      handler.call(this, oldValue, newValue);
  }
};

module.exports = SkyElement;
</script>