docs: Migrate section, view encapsulation, from Component Styles topic into its own topic. (angular#38986)

PR Close angular#38986

Author: David Shevitz

.pullapprove.yml

@@ -324,6 +324,7 @@ groups:
           'aio/content/examples/component-interaction/**',
           'aio/content/images/guide/component-interaction/**',
           'aio/content/guide/component-styles.md',
+          'aio/content/guide/view-encapsulation.md',
           'aio/content/examples/component-styles/**',
           'aio/content/guide/dependency-injection.md',
           'aio/content/examples/dependency-injection/**',

aio/content/guide/component-styles.md

@@ -119,7 +119,7 @@ The `/deep/` combinator also has the aliases `>>>`, and `::ng-deep`.
 
 Use `/deep/`, `>>>` and `::ng-deep` only with *emulated* view encapsulation.
 Emulated is the default and most commonly used view encapsulation. For more information, see the
-[Controlling view encapsulation](guide/component-styles#view-encapsulation) section.
+[View Encapsulation](guide/view-encapsulation) section.
 
 </div>
 
@@ -267,89 +267,3 @@ as explained in the [CLI wiki](https://github.com/angular/angular-cli/wiki/stori
 Style strings added to the `@Component.styles` array _must be written in CSS_ because the CLI cannot apply a preprocessor to inline styles.
 
 </div>
-
-{@a view-encapsulation}
-
-## View encapsulation
-
-As discussed earlier, component CSS styles are encapsulated into the component's view and don't
-affect the rest of the application.
-
-To control how this encapsulation happens on a *per
-component* basis, you can set the *view encapsulation mode* in the component metadata.
-Choose from the following modes:
-
-* `ShadowDom` view encapsulation uses the browser's native shadow DOM implementation (see
-  [Shadow DOM](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Shadow_DOM)
-  on the [MDN](https://developer.mozilla.org) site)
-  to attach a shadow DOM to the component's host element, and then puts the component
-  view inside that shadow DOM. The component's styles are included within the shadow DOM.
-
-* `Native` view encapsulation uses a now deprecated version of the browser's native shadow DOM implementation - [learn about the changes](https://hayato.io/2016/shadowdomv1/).
-
-* `Emulated` view encapsulation (the default) emulates the behavior of shadow DOM by preprocessing
-  (and renaming) the CSS code to effectively scope the CSS to the component's view.
-  For details, see [Inspecting generated CSS](guide/component-styles#inspect-generated-css) below.
-
-* `None` means that Angular does no view encapsulation.
-  Angular adds the CSS to the global styles.
-  The scoping rules, isolations, and protections discussed earlier don't apply.
-  This is essentially the same as pasting the component's styles into the HTML.
-
-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" header="src/app/quest-summary.component.ts"></code-example>
-
-`ShadowDom` view encapsulation only works on browsers that have native support
-for shadow DOM (see [Shadow DOM v1](https://caniuse.com/#feat=shadowdomv1) 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}
-
-## Inspecting generated CSS
-
-When using emulated view encapsulation, Angular preprocesses
-all component styles so that they approximate the standard shadow CSS scoping rules.
-
-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>
-    &lt;hero-team _ngcontent-pmm-5 _nghost-pmm-6>
-      &lt;h3 _ngcontent-pmm-6>Team&lt;/h3>
-    &lt;/hero-team>
-  &lt;/hero-detail>
-
-</code-example>
-
-There are two kinds of generated attributes:
-
-* An element that would be a shadow DOM host in native encapsulation has a
-  generated `_nghost` attribute. This is typically the case for component host elements.
-* An element within a component's view has a `_ngcontent` attribute
-that identifies to which host's emulated shadow DOM this element belongs.
-
-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;
-    border: 1px solid black;
-  }
-
-  h3[_ngcontent-pmm-6] {
-    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.

aio/content/guide/view-encapsulation.md

@@ -0,0 +1,83 @@
+# View encapsulation
+
+In Angular, component CSS styles are encapsulated into the component's view and don't
+affect the rest of the application.
+
+To control how this encapsulation happens on a *per
+component* basis, you can set the *view encapsulation mode* in the component metadata.
+Choose from the following modes:
+
+* `ShadowDom` view encapsulation uses the browser's native shadow DOM implementation (see
+  [Shadow DOM](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Shadow_DOM)
+  on the [MDN](https://developer.mozilla.org) site)
+  to attach a shadow DOM to the component's host element, and then puts the component
+  view inside that shadow DOM. The component's styles are included within the shadow DOM.
+
+* `Native` view encapsulation uses a now deprecated version of the browser's native shadow DOM implementation - [learn about the changes](https://hayato.io/2016/shadowdomv1/).
+
+* `Emulated` view encapsulation (the default) emulates the behavior of shadow DOM by preprocessing
+  (and renaming) the CSS code to effectively scope the CSS to the component's view.
+  For details, see [Inspecting generated CSS](guide/view-encapsulation#inspect-generated-css) below.
+
+* `None` means that Angular does no view encapsulation.
+  Angular adds the CSS to the global styles.
+  The scoping rules, isolations, and protections discussed earlier don't apply.
+  This is essentially the same as pasting the component's styles into the HTML.
+
+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" header="src/app/quest-summary.component.ts"></code-example>
+
+`ShadowDom` view encapsulation only works on browsers that have native support
+for shadow DOM (see [Shadow DOM v1](https://caniuse.com/#feat=shadowdomv1) 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}
+
+## Inspecting generated CSS
+
+When using emulated view encapsulation, Angular preprocesses
+all component styles so that they approximate the standard shadow CSS scoping rules.
+
+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>
+    &lt;hero-team _ngcontent-pmm-5 _nghost-pmm-6>
+      &lt;h3 _ngcontent-pmm-6>Team&lt;/h3>
+    &lt;/hero-team>
+  &lt;/hero-detail>
+
+</code-example>
+
+There are two kinds of generated attributes:
+
+* An element that would be a shadow DOM host in native encapsulation has a
+  generated `_nghost` attribute. This is typically the case for component host elements.
+* An element within a component's view has a `_ngcontent` attribute
+that identifies to which host's emulated shadow DOM this element belongs.
+
+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;
+    border: 1px solid black;
+  }
+
+  h3[_ngcontent-pmm-6] {
+    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.

aio/content/navigation.json

@@ -116,6 +116,11 @@
               "title": "Component Lifecycle",
               "tooltip": "Angular calls lifecycle hook methods on directives and components as it creates, changes, and destroys them."
             },
+            { 
+              "url": "guide/view-encapsulation",
+              "title": "View Encapsulation",
+              "tooltip": "Describes how component CSS styles are encapsulated into a component's view."
+            },
             {
               "url": "guide/component-interaction",
               "title": "Component Interaction",