fix(cdk/overlay): avoid having to manually load structural styles

Changes the overlay so it loads its structural styles automatically, instead of requiring the user to do it.

src/cdk/overlay/BUILD.bazel

@@ -18,13 +18,17 @@ ng_module(
         ["**/*.ts"],
         exclude = ["**/*.spec.ts"],
     ),
+    assets = [
+        ":overlay-prebuilt.css",
+    ],
     deps = [
         "//src:dev_mode_types",
         "//src/cdk/bidi",
         "//src/cdk/coercion",
         "//src/cdk/keycodes",
         "//src/cdk/platform",
         "//src/cdk/portal",
+        "//src/cdk/private",
         "//src/cdk/scrolling",
         "@npm//@angular/common",
         "@npm//@angular/core",

src/cdk/overlay/fullscreen-overlay-container.spec.ts

@@ -26,6 +26,7 @@ describe('FullscreenOverlayContainer', () => {
             // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
             fakeDocument = {
               body: document.body,
+              head: document.head,
               fullscreenElement: document.createElement('div'),
               fullscreenEnabled: true,
               addEventListener: (eventName: string, listener: EventListener) => {

src/cdk/overlay/overlay-container.ts

@@ -7,14 +7,34 @@
  */
 
 import {DOCUMENT} from '@angular/common';
-import {Inject, Injectable, OnDestroy} from '@angular/core';
+import {
+  Inject,
+  Injectable,
+  OnDestroy,
+  Component,
+  ChangeDetectionStrategy,
+  ViewEncapsulation,
+  inject,
+} from '@angular/core';
+import {_CdkPrivateStyleLoader} from '@angular/cdk/private';
 import {Platform, _isTestEnvironment} from '@angular/cdk/platform';
 
+@Component({
+  template: '',
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  encapsulation: ViewEncapsulation.None,
+  standalone: true,
+  styleUrl: 'overlay-prebuilt.css',
+  host: {'cdk-overlay-style-loader': ''},
+})
+export class _CdkOverlayStyleLoader {}
+
 /** Container inside which all overlays will render. */
 @Injectable({providedIn: 'root'})
 export class OverlayContainer implements OnDestroy {
   protected _containerElement: HTMLElement;
   protected _document: Document;
+  protected _styleLoader = inject(_CdkPrivateStyleLoader);
 
   constructor(
     @Inject(DOCUMENT) document: any,
@@ -34,6 +54,8 @@ export class OverlayContainer implements OnDestroy {
    * @returns the container element
    */
   getContainerElement(): HTMLElement {
+    this._loadStyles();
+
     if (!this._containerElement) {
       this._createContainer();
     }
@@ -84,4 +106,9 @@ export class OverlayContainer implements OnDestroy {
     this._document.body.appendChild(container);
     this._containerElement = container;
   }
+
+  /** Loads the structural styles necessary for the overlay to work. */
+  protected _loadStyles(): void {
+    this._styleLoader.load(_CdkOverlayStyleLoader);
+  }
 }

src/e2e-app/components/block-scroll-strategy/block-scroll-strategy-e2e.ts

@@ -1,5 +1,5 @@
 import {Component, inject} from '@angular/core';
-import {Overlay} from '@angular/cdk/overlay';
+import {Overlay, OverlayContainer} from '@angular/cdk/overlay';
 import {ScrollingModule} from '@angular/cdk/scrolling';
 
 @Component({
@@ -11,4 +11,9 @@ import {ScrollingModule} from '@angular/cdk/scrolling';
 })
 export class BlockScrollStrategyE2E {
   scrollStrategy = inject(Overlay).scrollStrategies.block();
+
+  constructor() {
+    // This loads the structural styles for the test.
+    inject(OverlayContainer).getContainerElement();
+  }
 }

src/material/core/_core.scss

@@ -15,7 +15,6 @@
   }
 
   @include cdk.a11y-visually-hidden();
-  @include cdk.overlay();
   @include cdk.text-field-autosize();
   @include cdk.text-field-autofill();
   @include private.structural-styling('mat');

tools/public_api_guard/cdk/overlay.md

@@ -4,6 +4,7 @@
 
 ```ts
 
+import { _CdkPrivateStyleLoader } from '@angular/cdk/private';
 import { CdkScrollable } from '@angular/cdk/scrolling';
 import { ComponentFactoryResolver } from '@angular/core';
 import { ComponentPortal } from '@angular/cdk/portal';
@@ -303,11 +304,14 @@ export class OverlayContainer implements OnDestroy {
     // (undocumented)
     protected _document: Document;
     getContainerElement(): HTMLElement;
+    protected _loadStyles(): void;
     // (undocumented)
     ngOnDestroy(): void;
     // (undocumented)
     protected _platform: Platform;
     // (undocumented)
+    protected _styleLoader: _CdkPrivateStyleLoader;
+    // (undocumented)
     static ɵfac: i0.ɵɵFactoryDeclaration<OverlayContainer, never>;
     // (undocumented)
     static ɵprov: i0.ɵɵInjectableDeclaration<OverlayContainer>;