ember-spaniel

Ember addon wrapping spaniel, a viewport tracking library, IntersectionObserver polyfill, and requestAnimationFrame task utility.

Compatibility

• Ember.js v3.4 or above
• Ember CLI v2.13 or above
• Node.js v8 or above

Installation

ember install my-addon

Usage

Including this addon will add Spaniel to your application, available for direct use in the app.

import * as spaniel from 'spaniel';

The rest of the API is contained in a service.

viewport service API

You can set your ember-spaniel config in config/environment.js, there are 3 options defaultRootMargin, watcherTime and watcherRatio.

The viewport service will look for a defaultRootMargin object property on the application config. If not found, will default to 0, 0, 0, 0. The watcherTime and watcherRatio will be used as the config of watcher return by getWatcher().

// environment.js
module.exports = {
  ...
  'ember-spaniel': {
    watcherTime: 100,
    watcherRatio: 0.8,
    defaultRootMargin: {
      top: 100,
      bottom: 200
    }
  }
}

onInViewportOnce(el, callback, { context, rootMargin, ratio, root, ALLOW_CACHED_SCHEDULER }) => Function

Register a callback that will be called when the provided element first enters the viewport. Will get called on the next requestAnimationFrame if the element is already in the viewport. Returns a function that, when called, will cancel and clear the callback.

Optionally includes the ability to specify a custom root, which defaults to window. When passing a custom root, the common case would include handling state invalidation (referenced below invalidate()).

An optional flag ALLOW_CACHED_SCHEDULER which defaults to true. This feature flag when passed as false will disable caching of getBoundingClientRect on elements within the Spaniel#ElementScheduler.

export default Ember.Component.extend({
  viewport: Ember.inject.service(),
  didInsertElement() {
    let viewport = this.get('viewport');
    let el = this.get('element');
    this.clearViewportCallback = viewport.onInViewportOnce(el, () => {
      console.log('I am in the viewport');
    });
  },
  willDestroyElement() {
    this._super(...arguments);
    this.clearViewportCallback();
  }
});

export default Ember.Component.extend({
  viewport: Ember.inject.service(),
  didInsertElement() {
    let viewport = this.get('viewport');
    let fooChildElement = this.get('element');

    this.clearViewportCallback = viewport.onInViewportOnce(fooChildElement, () => {
      console.log('I am in the viewport');
    }, {
      root: fooCustomRoot,
      ALLOW_CACHED_SCHEDULER: false
    });
  },
  willDestroyElement() {
    this._super(...arguments);
    this.clearViewportCallback();
  }
});

isInViewport(el, { ratio, rootMargin } = {}) => Promise

Returns a promise that resolves if the element is in the viewport, otherwise rejects.

export default Ember.Component.extend({
  viewport: Ember.inject.service(),
  didInsertElement() {
    let viewport = this.get('viewport');
    let el = this.get('element');
    viewport.isInViewport(el).then(() => {
      console.log('In the viewport');
    }, () => {
      console.log('Not in the viewport');
    });
  }
});

getWatcher()

The service has a Watcher instance available for direct use.

export default Ember.Component.extend({
  viewport: Ember.inject.service(),
  didInsertElement() {
    let watcher = this.get('viewport').getWatcher();
    let el = this.get('element');
    watcher.watch(el, (e) => {
      console.log(`${e} happened`);
    });
  }
});

invalidate()

Triggers Spaniel#invalidate on the viewport to invalidate cached state. Due to negative performance implications, this method should not be abused and as such should handle edge case scenarios only, such as when leveraging a custom root. The recommended pattern below binds an event to viewports custom root, that when fired triggers the viewports invalidate() method. Optionally leveraging Ember's Util #debounce method for improved performance and/or https://github.com/ember-lifeline/ember-lifeline#addeventlistener.

export default Ember.Component.extend({
  viewport: Ember.inject.service(),
  didInsertElement() {
    let viewport = this.get('viewport');
    let el = this.get('element');
    viewport.isInViewport(el).then(() => {
      console.log('In the viewport');
    }, () => {
      console.log('Not in the viewport');
    });

    fooCustomRoot.addEventListener('foo-event', this.onFooMethod.bind(this), false);
  },
  onFooMethod() {
    let viewport = this.get('viewport');

    viewport.invalidate();
  },
  willDestroyElement() {
    this._super(...arguments);
    let viewport = this.get('viewport');

    fooCustomRoot.removeEventListener('foo-event', this.onFooMethod.bind(this), false);
  }
});

Contributing

See the Contributing guide for details.

License

This project is licensed under the MIT License.