fix(viewport-ruler): fix server-side rendering errors when attempting to measure the viewport (#9870)

Fixes some errors being thrown by the `ViewportRuler` when attempting to measure the viewport or to get the scroll position while rendering on the server.

Relates to #9066.

Author: crisbeto

src/cdk/scrolling/viewport-ruler.ts

@@ -33,8 +33,8 @@ export class ViewportRuler implements OnDestroy {
   /** Subscription to streams that invalidate the cached viewport dimensions. */
   private _invalidateCache: Subscription;
 
-  constructor(platform: Platform, ngZone: NgZone) {
-    this._change = platform.isBrowser ? ngZone.runOutsideAngular(() => {
+  constructor(private _platform: Platform, ngZone: NgZone) {
+    this._change = _platform.isBrowser ? ngZone.runOutsideAngular(() => {
       return merge<Event>(fromEvent(window, 'resize'), fromEvent(window, 'orientationchange'));
     }) : observableOf();
 
@@ -51,7 +51,14 @@ export class ViewportRuler implements OnDestroy {
       this._updateViewportSize();
     }
 
-    return {width: this._viewportSize.width, height: this._viewportSize.height};
+    const output = {width: this._viewportSize.width, height: this._viewportSize.height};
+
+    // If we're not on a browser, don't cache the size since it'll be mocked out anyway.
+    if (!this._platform.isBrowser) {
+      this._viewportSize = null!;
+    }
+
+    return output;
   }
 
   /** Gets a ClientRect for the viewport's bounds. */
@@ -80,6 +87,12 @@ export class ViewportRuler implements OnDestroy {
 
   /** Gets the (top, left) scroll position of the viewport. */
   getViewportScrollPosition() {
+    // While we can get a reference to the fake document
+    // during SSR, it doesn't have getBoundingClientRect.
+    if (!this._platform.isBrowser) {
+      return {top: 0, left: 0};
+    }
+
     // The top-left-corner of the viewport is determined by the scroll position of the document
     // body, normally just (scrollLeft, scrollTop). However, Chrome and Firefox disagree about
     // whether `document.body` or `document.documentElement` is the scrolled element, so reading
@@ -107,7 +120,9 @@ export class ViewportRuler implements OnDestroy {
 
   /** Updates the cached viewport size. */
   private _updateViewportSize() {
-    this._viewportSize = {width: window.innerWidth, height: window.innerHeight};
+    this._viewportSize = this._platform.isBrowser ?
+        {width: window.innerWidth, height: window.innerHeight} :
+        {width: 0, height: 0};
   }
 }
 

src/universal-app/kitchen-sink/kitchen-sink.ts

@@ -42,8 +42,7 @@ import {
   CdkTableModule,
   DataSource
 } from '@angular/cdk/table';
-import {Overlay} from '@angular/cdk/overlay';
-
+import {ViewportRuler} from '@angular/cdk/scrolling';
 import {of as observableOf} from 'rxjs/observable/of';
 import {Observable} from 'rxjs/Observable';
 
@@ -75,13 +74,17 @@ export class KitchenSink {
   /** Data source for the CDK and Material table. */
   tableDataSource = new TableDataSource();
 
-  constructor(snackBar: MatSnackBar, dialog: MatDialog, overlay: Overlay) {
-    // Open a snack bar to do a basic sanity check of the overlays.
+  constructor(
+    snackBar: MatSnackBar,
+    dialog: MatDialog,
+    viewportRuler: ViewportRuler) {
     snackBar.open('Hello there');
+    dialog.open(TestDialog);
 
-    // TODO(crisbeto): use the noop scroll strategy until
-    // the fixes for the block scroll strategy get in.
-    dialog.open(TestDialog, {scrollStrategy: overlay.scrollStrategies.noop()});
+    // Do a sanity check on the viewport ruler.
+    viewportRuler.getViewportRect();
+    viewportRuler.getViewportSize();
+    viewportRuler.getViewportScrollPosition();
   }
 }