fix(tooltip): unable to type in input with tooltip on iOS

Fixes an issue, caused by HammerJS adding `user-select: none` to the trigger element, that prevents users from being able to type inside inputs on iOS, if they have a tooltip.

Fixes #8331.

Author: crisbeto

src/lib/tooltip/tooltip.spec.ts

@@ -43,7 +43,8 @@ describe('MatTooltip', () => {
         BasicTooltipDemo,
         ScrollableTooltipDemo,
         OnPushTooltipDemo,
-        DynamicTooltipsDemo
+        DynamicTooltipsDemo,
+        TooltipOnTextFields
       ],
       providers: [
         {provide: Platform, useValue: {IOS: false, isBrowser: true}},
@@ -667,6 +668,25 @@ describe('MatTooltip', () => {
     }));
   });
 
+  describe('special cases', () => {
+    it('should clear the `user-select` when a tooltip is set on a text field in iOS', () => {
+      TestBed.overrideProvider(Platform, {
+        useValue: {IOS: true, isBrowser: true}
+      });
+
+      const fixture = TestBed.createComponent(TooltipOnTextFields);
+      const instance = fixture.componentInstance;
+
+      fixture.detectChanges();
+
+      expect(instance.input.nativeElement.style.userSelect).toBeFalsy();
+      expect(instance.input.nativeElement.style.webkitUserSelect).toBeFalsy();
+
+      expect(instance.textarea.nativeElement.style.userSelect).toBeFalsy();
+      expect(instance.textarea.nativeElement.style.webkitUserSelect).toBeFalsy();
+    });
+  });
+
 });
 
 @Component({
@@ -752,6 +772,24 @@ class DynamicTooltipsDemo {
   }
 }
 
+@Component({
+  template: `
+    <input
+      #input
+      style="user-select: none; -webkit-user-select: none"
+      matTooltip="Something">
+
+    <textarea
+      #textarea
+      style="user-select: none; -webkit-user-select: none"
+      matTooltip="Another thing"></textarea>
+  `,
+})
+class TooltipOnTextFields {
+  @ViewChild('input') input: ElementRef;
+  @ViewChild('textarea') textarea: ElementRef;
+}
+
 /** Asserts whether a tooltip directive has a tooltip instance. */
 function assertTooltipInstance(tooltip: MatTooltip, shouldExist: boolean): void {
   // Note that we have to cast this to a boolean, because Jasmine will go into an infinite loop

src/lib/tooltip/tooltip.ts

@@ -176,6 +176,8 @@ export class MatTooltip implements OnDestroy {
     @Inject(MAT_TOOLTIP_SCROLL_STRATEGY) private _scrollStrategy,
     @Optional() private _dir: Directionality) {
 
+    const element: HTMLElement = _elementRef.nativeElement;
+
     // The mouse events shouldn't be bound on iOS devices, because
     // they can prevent the first tap from firing its click event.
     if (!_platform.IOS) {
@@ -184,9 +186,16 @@ export class MatTooltip implements OnDestroy {
 
       this._manualListeners
         .forEach((listener, event) => _elementRef.nativeElement.addEventListener(event, listener));
+    } else if (element.nodeName === 'INPUT' || element.nodeName === 'TEXTAREA') {
+      // When we bind a gesture event on an element (in this case `longpress`), HammerJS
+      // will add some inline styles by default, including `user-select: none`. This is
+      // problematic on iOS, because it will prevent users from typing in inputs. If
+      // we're on iOS and the tooltip is attached on an input or textarea, we clear
+      // the `user-select` to avoid these issues.
+      element.style.webkitUserSelect = element.style.userSelect = '';
     }
 
-    _focusMonitor.monitor(_elementRef.nativeElement, false).subscribe(origin => {
+    _focusMonitor.monitor(element, false).subscribe(origin => {
       // Note that the focus monitor runs outside the Angular zone.
       if (!origin) {
         _ngZone.run(() => this.hide(0));