From b1d300dc265604418afeb7f813b1b30de94b2b34 Mon Sep 17 00:00:00 2001
From: WilliamKoza <william.koza@gmail.com>
Date: Sun, 20 Jan 2019 14:12:52 +0100
Subject: [PATCH] fix(common): Prefer to use pageXOffset / pageYOffset instance
 of scrollX / scrollY (#28262)

This fix ensures a better cross-browser compatibility.
This fix has been used for angular.io.

PR Close #28262
---
 aio/src/app/shared/scroll.service.ts           |  2 +-
 packages/common/src/viewport_scroller.ts       |  6 +++---
 packages/common/test/viewport_scroller_spec.ts |  3 ++-
 packages/router/test/bootstrap.spec.ts         | 17 +++++++----------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/aio/src/app/shared/scroll.service.ts b/aio/src/app/shared/scroll.service.ts
index ab5f299b66..20b133055b 100644
--- a/aio/src/app/shared/scroll.service.ts
+++ b/aio/src/app/shared/scroll.service.ts
@@ -24,7 +24,7 @@ export class ScrollService implements OnDestroy {
   poppedStateScrollPosition: ScrollPosition|null = null;
   // Whether the browser supports the necessary features for manual scroll restoration.
   supportManualScrollRestoration: boolean = !!window && ('scrollTo' in window) &&
-      ('scrollX' in window) && ('scrollY' in window) && isScrollRestorationWritable();
+      ('pageXOffset' in window) && isScrollRestorationWritable();
 
   // Offset from the top of the document to bottom of any static elements
   // at the top (e.g. toolbar) + some margin
diff --git a/packages/common/src/viewport_scroller.ts b/packages/common/src/viewport_scroller.ts
index bbcf53ebbc..d3ff85d6fd 100644
--- a/packages/common/src/viewport_scroller.ts
+++ b/packages/common/src/viewport_scroller.ts
@@ -89,7 +89,7 @@ export class BrowserViewportScroller implements ViewportScroller {
    */
   getScrollPosition(): [number, number] {
     if (this.supportsScrolling()) {
-      return [this.window.scrollX, this.window.scrollY];
+      return [this.window.pageXOffset, this.window.pageYOffset];
     } else {
       return [0, 0];
     }
@@ -149,7 +149,7 @@ export class BrowserViewportScroller implements ViewportScroller {
    */
   private supportScrollRestoration(): boolean {
     try {
-      if (!this.window || !this.window.scrollTo) {
+      if (!this.supportsScrolling()) {
         return false;
       }
       // The `scrollRestoration` property could be on the `history` instance or its prototype.
@@ -166,7 +166,7 @@ export class BrowserViewportScroller implements ViewportScroller {
 
   private supportsScrolling(): boolean {
     try {
-      return !!this.window.scrollTo;
+      return !!this.window && !!this.window.scrollTo && 'pageXOffset' in this.window;
     } catch {
       return false;
     }
diff --git a/packages/common/test/viewport_scroller_spec.ts b/packages/common/test/viewport_scroller_spec.ts
index 006702e985..90713e62fd 100644
--- a/packages/common/test/viewport_scroller_spec.ts
+++ b/packages/common/test/viewport_scroller_spec.ts
@@ -15,7 +15,8 @@ describe('BrowserViewportScroller', () => {
   let windowSpy: any;
 
   beforeEach(() => {
-    windowSpy = jasmine.createSpyObj('window', ['history', 'scrollTo']);
+    windowSpy =
+        jasmine.createSpyObj('window', ['history', 'scrollTo', 'pageXOffset', 'pageYOffset']);
     windowSpy.history.scrollRestoration = 'auto';
     documentSpy = jasmine.createSpyObj('document', ['getElementById', 'getElementsByName']);
     scroller = new BrowserViewportScroller(documentSpy, windowSpy, null!);
diff --git a/packages/router/test/bootstrap.spec.ts b/packages/router/test/bootstrap.spec.ts
index f3ee2c51df..5c76c6b8e2 100644
--- a/packages/router/test/bootstrap.spec.ts
+++ b/packages/router/test/bootstrap.spec.ts
@@ -348,27 +348,24 @@ describe('bootstrap', () => {
     await router.navigateByUrl('/aa');
     window.scrollTo(0, 5000);
 
-    // IE 11 uses non-standard pageYOffset instead of scrollY
-    const getScrollY = () => window.scrollY !== undefined ? window.scrollY : window.pageYOffset;
-
     await router.navigateByUrl('/fail');
-    expect(getScrollY()).toEqual(5000);
+    expect(window.pageYOffset).toEqual(5000);
 
     await router.navigateByUrl('/bb');
     window.scrollTo(0, 3000);
 
-    expect(getScrollY()).toEqual(3000);
+    expect(window.pageYOffset).toEqual(3000);
 
     await router.navigateByUrl('/cc');
-    expect(getScrollY()).toEqual(0);
+    expect(window.pageYOffset).toEqual(0);
 
     await router.navigateByUrl('/aa#marker2');
-    expect(getScrollY()).toBeGreaterThanOrEqual(5900);
-    expect(getScrollY()).toBeLessThan(6000);  // offset
+    expect(window.pageYOffset).toBeGreaterThanOrEqual(5900);
+    expect(window.pageYOffset).toBeLessThan(6000);  // offset
 
     await router.navigateByUrl('/aa#marker3');
-    expect(getScrollY()).toBeGreaterThanOrEqual(8900);
-    expect(getScrollY()).toBeLessThan(9000);
+    expect(window.pageYOffset).toBeGreaterThanOrEqual(8900);
+    expect(window.pageYOffset).toBeLessThan(9000);
     done();
   });