From a1861704d8de18fb0f8d974616a878fd3068be2f Mon Sep 17 00:00:00 2001
From: Laurentiu Amagdei <lau32on@gmail.com>
Date: Mon, 3 Jun 2019 06:44:42 +0200
Subject: [PATCH] fix:(tabs) add call for rechecking tab scroll distance Add
 call to scroll the tabs header after initialising header pagination, to
 accurately calculate the scroll distance.

Fixes #12889
---
 src/material/tabs/tab-header.spec.ts | 28 ++++++++++++++++++++++++++++
 src/material/tabs/tab-header.ts      |  1 +
 2 files changed, 29 insertions(+)

diff --git a/src/material/tabs/tab-header.spec.ts b/src/material/tabs/tab-header.spec.ts
index 45c0ba33d5b8..50d877631d70 100644
--- a/src/material/tabs/tab-header.spec.ts
+++ b/src/material/tabs/tab-header.spec.ts
@@ -604,6 +604,34 @@ describe('MatTabHeader', () => {
       expect(tabHeaderElement.classList).toContain(enabledClass);
     });
 
+    it('should scroll to last tab', async(() => {
+      const tabs = [
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+        {label: 'tab one'},
+      ];
+
+      fixture = TestBed.createComponent(SimpleTabHeaderApp);
+      fixture.detectChanges();
+
+      const component = fixture.componentInstance;
+      component.tabs = tabs;
+      component.selectedIndex = tabs.length - 1;
+      fixture.detectChanges();
+
+      fixture.whenRenderingDone()
+        .then(() => {
+          expect(component.tabHeader._disableScrollAfter).toBeTruthy();
+          expect(component.tabHeader.scrollDistance)
+            .toEqual(component.tabHeader._getMaxScrollDistance());
+        });
+    }));
+
   });
 });
 
diff --git a/src/material/tabs/tab-header.ts b/src/material/tabs/tab-header.ts
index 5783f1858f93..15edcc0c0ec7 100644
--- a/src/material/tabs/tab-header.ts
+++ b/src/material/tabs/tab-header.ts
@@ -238,6 +238,7 @@ export class MatTabHeader extends _MatTabHeaderMixinBase
     const dirChange = this._dir ? this._dir.change : observableOf(null);
     const resize = this._viewportRuler.change(150);
     const realign = () => {
+      this._scrollToLabel(this._selectedIndex);
       this.updatePagination();
       this._alignInkBarToSelectedTab();
     };