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custom-style.html
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custom-style.html
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<!--
@license
Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->
<link rel="import" href="style-util.html">
<link rel="import" href="style-transformer.html">
<link rel="import" href="style-defaults.html">
<!--
The `custom-style` extension of the native `<style>` element allows defining styles
in the main document that can take advantage of several special features of
Polymer's styling system:
* Document styles defined in a `custom-style` will be shimmed to ensure they do
not leak into local DOM when running on browsers without non-native Shadow DOM.
* Shadow DOM-specific `/deep/` and `::shadow` combinators will be shimmed on
browsers without non-native Shadow DOM.
* Custom properties used by Polymer's shim for cross-scope styling
may be defined in an `custom-style`.
* An `include` attribute may be specified to pull in style data from a
`dom-module` matching the include attribute. By using `include`, style data
can be shared between multiple `custom-style` elements.
Example:
```html
<!doctype html>
<html>
<head>
<script src="components/webcomponentsjs/webcomponents-lite.js"></script>
<link rel="import" href="components/polymer/polymer.html">
<style is="custom-style">
/* Will be prevented from affecting local DOM of Polymer elements */
* {
box-sizing: border-box;
}
/* Can use /deep/ and ::shadow combinators */
body /deep/ .my-special-view::shadow #thing-inside {
background: yellow;
}
/* Custom properties that inherit down the document tree may be defined */
body {
--my-toolbar-title-color: green;
}
</style>
</head>
<body>
...
</body>
</html>
```
Note, all features of `custom-style` are available when defining styles as part of Polymer elements (e.g. `<style>` elements within `<dom-module>`'s used for defining Polymer elements. The `custom-style` extension should only be used for defining document styles, outside of a custom element's local DOM.
-->
<script>
(function() {
var nativeShadow = Polymer.Settings.useNativeShadow;
var propertyUtils = Polymer.StyleProperties;
var styleUtil = Polymer.StyleUtil;
var cssParse = Polymer.CssParse;
var styleDefaults = Polymer.StyleDefaults;
var styleTransformer = Polymer.StyleTransformer;
Polymer({
is: 'custom-style',
extends: 'style',
_template: null,
properties: {
// include is a property so that it deserializes
/**
* Specify `include` to identify a `dom-module` containing style data which
* should be used within the `custom-style`. By using `include` style data
* may be shared between multiple different `custom-style` elements.
*/
include: String
},
ready: function() {
// NOTE: we cannot just check attached because custom elements in
// HTMLImports do not get attached.
this._tryApply();
},
attached: function() {
this._tryApply();
},
_tryApply: function() {
if (!this._appliesToDocument) {
// only apply variables iff this style is not inside a dom-module
if (this.parentNode &&
(this.parentNode.localName !== 'dom-module')) {
this._appliesToDocument = true;
// used applied element from HTMLImports polyfill or this
var e = this.__appliedElement || this;
styleDefaults.addStyle(e);
// we may not have any textContent yet due to parser yielding
// if so, wait until we do...
if (e.textContent || this.include) {
this._apply();
} else {
var self = this;
var observer = new MutationObserver(function() {
observer.disconnect();
self._apply();
});
observer.observe(e, {childList: true});
}
}
}
},
// polyfill this style with root scoping and
// apply custom properties!
_apply: function() {
// used applied element from HTMLImports polyfill or this
var e = this.__appliedElement || this;
if (this.include) {
e.textContent = styleUtil.cssFromModules(this.include, true) +
e.textContent;
}
if (e.textContent) {
styleUtil.forEachStyleRule(styleUtil.rulesForStyle(e), function(rule) {
styleTransformer.documentRule(rule);
});
// Allow all custom-styles defined in this turn to register
// before applying any properties. This helps ensure that all properties
// are defined before any are consumed.
// Premature application of properties can occur in 2 cases:
// (1) A property `--foo` is consumed in a custom-style
// before another custom-style produces `--foo`.
// In general, we require custom properties to be defined before being
// used in elements so supporting this for custom-style
// is dubious but is slightly more like native properties where this
// is supported.
// (2) A set of in order styles (A, B) are re-ordered due to a parser
// yield that makes A wait for textContent. This reorders its
// `_apply` after B.
// This case should only occur with native webcomponents.
var self = this;
requestAnimationFrame(function() {
self._applyCustomProperties(e);
});
}
},
_applyCustomProperties: function(element) {
this._computeStyleProperties();
var props = this._styleProperties;
var rules = styleUtil.rulesForStyle(element);
element.textContent = styleUtil.toCssText(rules, function(rule) {
var css = rule.cssText = rule.parsedCssText;
if (rule.propertyInfo && rule.propertyInfo.cssText) {
// remove property assignments
// so next function isn't confused
// NOTE: we have 3 categories of css:
// (1) normal properties,
// (2) custom property assignments (--foo: red;),
// (3) custom property usage: border: var(--foo); @apply(--foo);
// In elements, 1 and 3 are separated for efficiency; here they
// are not and this makes this case unique.
css = cssParse.removeCustomPropAssignment(css);
// replace with reified properties, scenario is same as mixin
rule.cssText = propertyUtils.valueForProperties(css, props);
}
});
}
});
})();
</script>