Eric Seidel bdaf418370 Add super-basic sky widgets.
Eventually we'll want to replace these with something
fancier like polymer, but this exercise helped us
find several bugs in the engine as well as
removed one more blocker from using Sky to
replace mojo/views usage in mojo/examples.

R=esprehn@chromium.org
BUG=443439

Review URL: https://codereview.chromium.org/809233002
2014-12-18 13:01:43 -08:00
..
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SkyElement

SkyElement is the framework for creating...yup...Sky Elements. It take heavy inspriation from Polymer and isn't very fully featured...yet

Declaring an element

<import src="../path/to/sky-element.sky" as="SkyElement" />
<template>
  <my-other-element>Hello, {{ place }}</my-other-element>
</template>
<script>
// SkyElement takes a single object as it's only parameter
SkyElement({
  name: 'my-element', // required. The element's tag-name
  attached: function() {
    this.place = 'World';
  }, // optional
  detached: function() {}, // optional
  attributeChanged: function(attrName, newValue, oldValue) {} // optional
});
</script>

Note that an element's declared ShadowDOM is the previous <template> element to the <script> element which defines the element.

Databinding

SkyElement's databinding support is derived from Polymer's. At the moment, there are some key differences:

There is not yet support for

  • Declarative event handlers
  • Inline expressions
  • Self-observation (e.g. fooChanged() gets invoked when this.foo is changed)
  • Computed properties (e.g. the computed block)
  • Conditional attributes (e.g. <my-foo checked?="{{ val }}")

Also, because there are so few built-in elements in Sky, the default behavior of HTMLElement with bindings is to assign to the property. e.g.

<my-foo bar="{{ bas }}">

Will not setAttribute on the my-foo, instead it will assign to the bar property of my-foo. There are two exceptions to this: class & style -- those stillsetAttribute.