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docs: Component Styles guide for CLI (#19791)

This commit is contained in:
Ward Bell 2017-11-03 11:12:34 -07:00 committed by Victor Berchet
parent 1d19d61970
commit 567cc26b8e
6 changed files with 121 additions and 143 deletions
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2
aio/content/examples/component-styles/e2e/app.e2e-spec.ts
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@ -13,7 +13,7 @@ describe('Component Style Tests', function () {
let externalH1 = element(by.css('body > h1'));
// Note: sometimes webdriver returns the fontWeight as "normal",
// othertimes as "400", both of which are equal in CSS terms.
// other times as "400", both of which are equal in CSS terms.
expect(componentH1.getCssValue('fontWeight')).toMatch(/normal|400/);
expect(externalH1.getCssValue('fontWeight')).not.toMatch(/normal|400/);
});

3
aio/content/examples/component-styles/plnkr.json
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@ -4,7 +4,8 @@
"files": [
"!**/*.d.ts",
"!**/*.js",
"!**/*.native.*"
"!**/*.native.*",
"!**/*.[1].*"
],
"tags": ["CSS"]
}

3
aio/content/examples/component-styles/src/app/hero-app.component.1.css Normal file
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@ -0,0 +1,3 @@
h1 {
font-weight: normal;
}

25
aio/content/examples/component-styles/src/app/hero-app.component.1.ts Normal file
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@ -0,0 +1,25 @@
import { Component, HostBinding } from '@angular/core';
import { Hero } from './hero';
// #docregion
@Component({
selector: 'app-root',
template: `
<h1>Tour of Heroes</h1>
<app-hero-main [hero]="hero"></app-hero-main>
`,
styleUrls: ['./hero-app.component.css']
})
export class HeroAppComponent {
// #enddocregion
hero = new Hero(
'Human Torch',
['Mister Fantastic', 'Invisible Woman', 'Thing']
);
@HostBinding('class') get themeClass() {
return 'theme-light';
}
// #docregion
}
// #enddocregion

3
aio/content/examples/component-styles/src/app/hero-app.component.ts
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@ -6,7 +6,8 @@ import { Hero } from './hero';
selector: 'app-root',
template: `
<h1>Tour of Heroes</h1>
<app-hero-main [hero]=hero></app-hero-main>`,
<app-hero-main [hero]="hero"></app-hero-main>
`,
styles: ['h1 { font-weight: normal; }']
})
export class HeroAppComponent {

228
aio/content/guide/component-styles.md
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@ -9,23 +9,9 @@ with components, enabling a more modular design than regular stylesheets.
This page describes how to load and apply these component styles.
<!--
## Table Of Contents
* [Using component styles](guide/component-styles#using-component-styles)
* [Special selectors](guide/component-styles#special-selectors)
* [Loading styles into components](guide/component-styles#loading-styles)
* [Controlling view encapsulation: native, emulated, and none](guide/component-styles#view-encapsulation)
* [Appendix 1: Inspecting the CSS generated in emulated view encapsulation](guide/component-styles#inspect-generated-css)
* [Appendix 2: Loading styles with relative URLs](guide/component-styles#relative-urls)
-->
You can run the <live-example></live-example> in Plunker and download the code from there.
## Using component styles
For every Angular component you write, you may define not only an HTML template,
@ -36,34 +22,43 @@ One way to do this is to set the `styles` property in the component metadata.
The `styles` property takes an array of strings that contain CSS code.
Usually you give it one string, as in the following example:
<code-example path="component-styles/src/app/hero-app.component.ts" title="src/app/hero-app.component.ts" linenums="false">
</code-example>
## Style scope
<div class="alert is-critical">
The styles specified in `@Component` metadata _apply only within the template of that component_.
</div>
They are _not inherited_ by any components nested within the template nor by any content projected into the component.
In this example, the `h1` style applies only to the `HeroAppComponent`,
not to the nested `HeroMainComponent` nor to `<h1>` tags anywhere else in the application.
This scoping restriction is a ***styling modularity feature***.
* You can use the CSS class names and selectors that make the most sense in the context of each component.
The selectors you put into a component's styles apply only within the template
of that component. The `h1` selector in the preceding example applies only to the `<h1>` tag
in the template of `HeroAppComponent`. Any `<h1>` elements elsewhere in
the application are unaffected.
This is a big improvement in modularity compared to how CSS traditionally works.
* You can use the CSS class names and selectors that make the most sense in the context of each component.
* Class names and selectors are local to the component and don't collide with
classes and selectors used elsewhere in the application.
* Changes to styles elsewhere in the application don't affect the component's styles.
* You can co-locate the CSS code of each component with the TypeScript and HTML code of the component,
which leads to a neat and tidy project structure.
* You can change or remove component CSS code without searching through the
whole application to find where else the code is used.
{@a special-selectors}
## Special selectors
Component styles have a few special *selectors* from the world of shadow DOM style scoping
@ -78,11 +73,8 @@ targeting elements *inside* the component's template).
<code-example path="component-styles/src/app/hero-details.component.css" region="host" title="src/app/hero-details.component.css" linenums="false">
</code-example>
The `:host` selector is the only way to target the host element. You can't reach
the host element from inside the component with other selectors because it's not part of the
component's own template. The host element is in a parent component's template.
@ -92,13 +84,9 @@ including another selector inside parentheses after `:host`.
The next example targets the host element again, but only when it also has the `active` CSS class.
<code-example path="component-styles/src/app/hero-details.component.css" region="hostfunction" title="src/app/hero-details.component.css" linenums="false">
</code-example>
### :host-context
Sometimes it's useful to apply styles based on some condition *outside* of a component's view.
@ -112,13 +100,9 @@ up to the document root. The `:host-context()` selector is useful when combined
The following example applies a `background-color` style to all `<h2>` elements *inside* the component, only
if some ancestor element has the CSS class `theme-light`.
<code-example path="component-styles/src/app/hero-details.component.css" region="hostcontext" title="src/app/hero-details.component.css" linenums="false">
</code-example>
### (deprecated) `/deep/`, `>>>`, and `::ng-deep`
Component styles normally apply only to the HTML in the component's own template.
@ -165,90 +149,80 @@ There are several ways to add styles to a component:
The scoping rules outlined earlier apply to each of these loading patterns.
### Styles in metadata
### Styles in component metadata
You can add a `styles` array property to the `@Component` decorator.
Each string in the array (usually just one string) defines the CSS.
Each string in the array defines some CSS for this component.
<code-example path="component-styles/src/app/hero-app.component.ts" title="src/app/hero-app.component.ts">
<code-example path="component-styles/src/app/hero-app.component.ts" title="src/app/hero-app.component.ts (CSS inline)">
</code-example>
<div class="alert is-critical">
### Style URLs in metadata
You can load styles from external CSS files by adding a `styleUrls` attribute
into a component's `@Component` decorator:
<code-example path="component-styles/src/app/hero-details.component.ts" region="styleurls" title="src/app/hero-details.component.ts">
</code-example>
<div class="alert is-important">
The URL is relative to the *application root*, which is usually the
location of the `index.html` web page that hosts the application.
The style file URL is *not* relative to the component file.
That's why the example URL begins `src/app/`.
To specify a URL relative to the component file, see [Appendix 2](guide/component-styles#relative-urls).
Reminder: these styles apply _only to this component_.
They are _not inherited_ by any components nested within the template nor by any content projected into the component.
</div>
The CLI defines an empty `styles` array when you create the component with the `--inline-styles` flag.
<code-example language="sh" class="code-shell">
ng generate component hero-app --inline-style
</code-example>
### Style files in component metadata
You can load styles from external CSS files by adding a `styleUrls` property
to a component's `@Component` decorator:
<code-tabs>
<code-pane title="src/app/hero-app.component.ts (CSS in file)" path="component-styles/src/app/hero-app.component.1.ts"></code-pane>
<code-pane title="src/app/hero-app.component.css" path="component-styles/src/app/hero-app.component.1.css"></code-pane>
</code-tabs>
<div class="alert is-critical">
Reminder: the styles in the style file apply _only to this component_.
They are _not inherited_ by any components nested within the template nor by any content projected into the component.
</div>
<div class="l-sub-section">
If you use module bundlers like Webpack, you can also use the `styles` attribute
to load styles from external files at build time. You could write:
`styles: [require('my.component.css')]`
Set the `styles` property, not the `styleUrls` property. The module
bundler loads the CSS strings, not Angular.
Angular sees the CSS strings only after the bundler loads them.
To Angular, it's as if you wrote the `styles` array by hand.
For information on loading CSS in this manner, refer to the module bundler's documentation.
You can specify more than one styles file or even a combination of `style` and `styleUrls`.
</div>
The CLI creates an empty styles file for you by default and references that file in the component's generated `styleUrls`.
<code-example language="sh" class="code-shell">
ng generate component hero-app
</code-example>
### Template inline styles
You can embed styles directly into the HTML template by putting them
You can embed CSS styles directly into the HTML template by putting them
inside `<style>` tags.
<code-example path="component-styles/src/app/hero-controls.component.ts" region="inlinestyles" title="src/app/hero-controls.component.ts">
</code-example>
### Template link tags
You can also embed `<link>` tags into the component's HTML template.
As with `styleUrls`, the link tag's `href` URL is relative to the
application root, not the component file.
You can also write `<link>` tags into the component's HTML template.
<code-example path="component-styles/src/app/hero-team.component.ts" region="stylelink" title="src/app/hero-team.component.ts">
</code-example>
<div class="alert is-critical">
The link tag's `href` URL must be relative to the
_**application root**_, not relative to the component file.
When building with the CLI, be sure to include the linked style file among the assets to be copied to the server as described in the [CLI documentation](https://github.com/angular/angular-cli/wiki/stories-asset-configuration).
</div>
### CSS @imports
@ -256,20 +230,39 @@ You can also import CSS files into the CSS files using the standard CSS `@import
For details, see [`@import`](https://developer.mozilla.org/en/docs/Web/CSS/@import)
on the [MDN](https://developer.mozilla.org) site.
In this case, the URL is relative to the CSS file into which you're importing.
<code-example path="component-styles/src/app/hero-details.component.css" region="import" title="src/app/hero-details.component.css (excerpt)">
</code-example>
### External and global style files
When building with the CLI, you must configure the `.angular-cli.json` to include _all external assets_, including external style files.
Register **global** style files in the `styles` section which, by default, is pre-configured with the global `styles.css` file.
See the [CLI documentation](https://github.com/angular/angular-cli/wiki/stories-global-styles) to learn more.
### Non-CSS style files
You can write style files in [sass](http://sass-lang.com/), [less](http://lesscss.org/), or [stylus](http://stylus-lang.com/) and specify those files in the `styleUrls` metadata, e.g.,
<code-example>
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
...
</code-example>
The CLI build process runs the corresponding CSS pre-processors.
You can also configure the CLI to default to your preferred CSS pre-processer
as explained in the [CLI documentation](https://github.com/angular/angular-cli/wiki/stories-css-preprocessors).
{@a view-encapsulation}
## View encapsulation
As discussed earlier, component CSS styles are encapsulated into the component's view and don't
@ -296,25 +289,18 @@ Choose from the following modes:
To set the components encapsulation mode, use the `encapsulation` property in the component metadata:
<code-example path="component-styles/src/app/quest-summary.component.ts" region="encapsulation.native" title="src/app/quest-summary.component.ts" linenums="false">
</code-example>
`Native` view encapsulation only works on browsers that have native support
for shadow DOM (see [Shadow DOM v0](http://caniuse.com/#feat=shadowdom) on the
[Can I use](http://caniuse.com) site). The support is still limited,
which is why `Emulated` view encapsulation is the default mode and recommended
in most cases.
{@a inspect-generated-css}
## Appendix: Inspecting generated CSS
## Inspecting generated CSS
When using emulated view encapsulation, Angular preprocesses
all component styles so that they approximate the standard shadow CSS scoping rules.
@ -323,7 +309,6 @@ In the DOM of a running Angular application with emulated view
encapsulation enabled, each DOM element has some extra attributes
attached to it:
<code-example format="">
&lt;hero-details _nghost-pmm-5>
&lt;h2 _ngcontent-pmm-5>Mister Fantastic&lt;/h2>
@ -334,8 +319,6 @@ attached to it:
</code-example>
There are two kinds of generated attributes:
* An element that would be a shadow DOM host in native encapsulation has a
@ -347,7 +330,6 @@ The exact values of these attributes aren't important. They are automatically
generated and you never refer to them in application code. But they are targeted
by the generated component styles, which are in the `<head>` section of the DOM:
<code-example format="">
[_nghost-pmm-5] {
display: block;
@ -358,42 +340,8 @@ by the generated component styles, which are in the `<head>` section of the DOM:
background-color: white;
border: 1px solid #777;
}
</code-example>
These styles are post-processed so that each selector is augmented
with `_nghost` or `_ngcontent` attribute selectors.
These extra selectors enable the scoping rules described in this page.
{@a relative-urls}
## Appendix: Loading with relative URLs
It's common practice to split a component's code, HTML, and CSS into three separate files in the same directory:
<code-example format="nocode">
quest-summary.component.ts
quest-summary.component.html
quest-summary.component.css
</code-example>
You include the template and CSS files by setting the `templateUrl` and `styleUrls` metadata properties respectively.
Because these files are co-located with the component,
it would be nice to refer to them by name without also having to specify a path back to the root of the application.
You can use a relative URL by prefixing your filenames with `./`:
<code-example path="component-styles/src/app/quest-summary.component.ts" title="src/app/quest-summary.component.ts">
</code-example>