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d2l-polymer-behaviors
Advanced tools
d2l-polymer-behaviors
Shared Polymer-based behaviors and modules for implementing and consuming web components.
Installation
d2l-polymer-behaviors can be installed from Bower:
bower install d2l-polymer-behaviors
Usage
Include the webcomponents.js "lite" polyfill (for browsers who don't natively support web components), then import the component or scripts as needed.
<head>
<script src="https://s.brightspace.com/lib/webcomponentsjs/0.7.21/webcomponents-lite.min.js"></script>
<link rel="import" href="../d2l-polymer-behaviors/d2l-dom-focus.html">
</head>
Methods
D2L.Dom
// returns null or the closest ancestor that fulfills the specified predicate fxn
D2L.Dom.findComposedAncestor(node, predicate);
// gets the composed children (including shadow children & distributed children)
D2L.Dom.getComposedChildren(element);
// gets the composed parent (including shadow host & insertion points)
D2L.Dom.getComposedParent(node);
// returns true/false whether the specified ancestorNode is an ancestor of node
D2L.Dom.isComposedAncestor(ancestorNode, node);
// browser consistent implementation of HTMLElement.offsetParent
D2L.Dom.getOffsetParent(node);
D2L.Dom.Focus
// get the composed active element (i.e. the actual element that has focus)
D2L.Dom.Focus.getComposedActiveElement();
// get first focusable child or descendant
D2L.Dom.Focus.getFirstFocusableDescendant(element);
// get last focusable child or descendant
D2L.Dom.Focus.getLastFocusableDescendant(element);
// get the next focusable child, sibling, etc.
D2L.Dom.Focus.getNextFocusable(element);
// get the previous focusable child, sibling, etc.
D2L.Dom.Focus.getPreviousFocusable(element);
// get the nearest focusable ancestor
D2L.Dom.Focus.getPreviousFocusableAncestor(element);
// check is focusable (tabindex or white-listed elements)
D2L.Dom.Focus.isFocusable(element);
D2L.Dom.Visibility
// checks DOM visibility (includes inline & computed style of element and ancestors)
// ... does not check opacity, elements hidden due to overflow or scrolled out of view
D2L.Dom.Visibility.isVisible(element);
D2L.Id
// gets a unique indexed id (for lifetime of page)
D2L.Id.getUniqueId();
Behaviors
D2L.PolymerBehaviors.FocusableArrowKeysBehavior
The FocusableArrowKeysBehavior can be used for managing focus with the arrow keys.
- right/down - focuses next element, or first if currently at the end
- left/up - focuses previous element, or last if currently at beginning
- home - focuses first
- end - focuses last
// include the behavior
behaviors: [
D2L.PolymerBehaviors.FocusableArrowKeysBehavior
],
attached: function() {
Polymer.RenderStatus.afterNextRender(this, function() {
// indicate the direction (default is leftright)
this.arrowKeyFocusablesDirection = 'updown';
// required container element of focusables (used to listen for key events)
this.arrowKeyFocusablesContainer = container;
// required provider method that can return list of focusables - possible async
this.arrowKeyFocusablesProvider = function() {
// simple case
return Promise.resolve(focusables);
// other cases (ex. check visibility when querying focusables)
return new Promise(function(resolve) {
fastdom.measure(function() {
// ...
resolve(focusables);
});
});
};
// optional callback before focus is applied
this.arrowKeyFocusablesOnBeforeFocus = function(elem) {
return new Promise(function(resolve) {
// do some stuff
resolve();
});
};
});
}
D2L.PolymerBehaviors.VisibleOnAncestorBehavior
The VisibleOnAncestorBehavior can be used to show an element when a specified ancestor is being hovered, or a child of the ancestor has the focus. Likewise, the element will be hidden if the specified ancestor is not being hovered and none of its children have the focus. To define a component with this behavior, simply include the styles and behavior as shown in the example below.
<dom-module id="d2l-example">
<template>
<style include="d2l-visible-on-ancestor-styles"></style>
</template>
<script>
Polymer({
is: 'd2l-example',
behaviors: [
D2L.PolymerBehaviors.VisibleOnAncestorBehavior
]
});
</script>
</dom-module>
The consumer of d2l-example adds the d2l-visible-on-ancestor-target class to the desired ancestor that will be the target for mouse and focus events. If the user hovers the target, or focuses any element contained within, d2l-example will be displayed.
<div class="d2l-visible-on-ancestor-target">
...
<d2l-example visible-on-ancestor></d2l-example>
...
</div>
Usage in Production
In production, it's recommended to use a build tool like Vulcanize to combine all your web components into a single import file. More from the Polymer Docs: Optimize for Production...
Coding styles
See the VUI Best Practices & Style Guide for information on VUI naming conventions, plus information about the EditorConfig rules used in this repo.
Versioning
Commits and PR merges to master will automatically do a minor version bump which will:
- Update the version in
package.json - Add a tag matching the new version
- Create a github release matching the new version
By using either [increment major] or [increment patch] notation inside your merge message, you can overwrite the default version upgrade of minor to the position of your choice.
FAQs
Shared Polymer behaviors for use in web components
We found that d2l-polymer-behaviors demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
Package last updated on 19 Aug 2020
Did you know?
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