feat(overlay): add scroll handling strategies

* Adds the `scrollStrategy` option to the overlay state, allowing the consumer to specify what scroll handling strategy they'd want to use. Also includes a `ScrollStrategy` interface that users can utilize to build their own strategies.
* Adds the `RepositionScrollStrategy`, `CloseScrollStrategy` and `NoopScrollStrategy` as initial, out-of-the-box strategies.
* Sets the `RepositionScrollStrategy` by default on all the connected overlays and removes some repetitive logic from the tooltip, autocomplete, menu and select.

**Note:** I'll add a `BlockScrollStrategy` in a follow-up PR. I wanted to keep this one shorter.

Relates to angular#4093.

src/lib/autocomplete/autocomplete-trigger.ts

@@ -13,7 +13,7 @@ import {
 } from '@angular/core';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
 import {DOCUMENT} from '@angular/platform-browser';
-import {Overlay, OverlayRef, OverlayState, TemplatePortal} from '../core';
+import {Overlay, OverlayRef, OverlayState, TemplatePortal, RepositionScrollStrategy} from '../core';
 import {MdAutocomplete} from './autocomplete';
 import {PositionStrategy} from '../core/overlay/position/position-strategy';
 import {ConnectedPositionStrategy} from '../core/overlay/position/connected-position-strategy';
@@ -76,9 +76,6 @@ export class MdAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   /** The subscription to positioning changes in the autocomplete panel. */
   private _panelPositionSubscription: Subscription;
 
-  /** Subscription to global scroll events. */
-  private _scrollSubscription: Subscription;
-
   /** Strategy that is used to position the panel. */
   private _positionStrategy: ConnectedPositionStrategy;
 
@@ -139,12 +136,6 @@ export class MdAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
       this._subscribeToClosingActions();
     }
 
-    if (!this._scrollSubscription) {
-      this._scrollSubscription = this._scrollDispatcher.scrolled(0, () => {
-        this._overlayRef.updatePosition();
-      });
-    }
-
     this.autocomplete._setVisibility();
     this._floatPlaceholder();
     this._panelOpen = true;
@@ -156,11 +147,6 @@ export class MdAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
       this._overlayRef.detach();
     }
 
-    if (this._scrollSubscription) {
-      this._scrollSubscription.unsubscribe();
-      this._scrollSubscription = null;
-    }
-
     this._panelOpen = false;
     this._resetPlaceholder();
 
@@ -374,6 +360,7 @@ export class MdAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
     overlayState.positionStrategy = this._getOverlayPosition();
     overlayState.width = this._getHostWidth();
     overlayState.direction = this._dir ? this._dir.value : 'ltr';
+    overlayState.scrollStrategy = new RepositionScrollStrategy(this._scrollDispatcher);
     return overlayState;
   }
 

src/lib/core/core.ts

@@ -51,6 +51,10 @@ export * from './overlay/position/global-position-strategy';
 export * from './overlay/position/connected-position-strategy';
 export * from './overlay/position/connected-position';
 export {ScrollDispatcher} from './overlay/scroll/scroll-dispatcher';
+export {ScrollStrategy} from './overlay/scroll/scroll-strategy';
+export {RepositionScrollStrategy} from './overlay/scroll/reposition-scroll-strategy';
+export {CloseScrollStrategy} from './overlay/scroll/close-scroll-strategy';
+export {NoopScrollStrategy} from './overlay/scroll/noop-scroll-strategy';
 
 // Gestures
 export {GestureConfig} from './gestures/gesture-config';

src/lib/core/overlay/overlay-directives.ts

@@ -23,8 +23,11 @@ import {PortalModule} from '../portal/portal-directives';
 import {ConnectedPositionStrategy} from './position/connected-position-strategy';
 import {Dir, LayoutDirection} from '../rtl/dir';
 import {Scrollable} from './scroll/scrollable';
+import {RepositionScrollStrategy} from './scroll/reposition-scroll-strategy';
+import {ScrollStrategy} from './scroll/scroll-strategy';
 import {coerceBooleanProperty} from '../coercion/boolean-property';
 import {ESCAPE} from '../keyboard/keycodes';
+import {ScrollDispatcher} from './scroll/scroll-dispatcher';
 import {Subscription} from 'rxjs/Subscription';
 
 
@@ -119,6 +122,9 @@ export class ConnectedOverlayDirective implements OnDestroy {
   /** The custom class to be set on the backdrop element. */
   @Input() backdropClass: string;
 
+  /** Strategy to be used when handling scroll events while the overlay is open. */
+  @Input() scrollStrategy: ScrollStrategy = new RepositionScrollStrategy(this._scrollDispatcher);
+
   /** Whether or not the overlay should attach a backdrop. */
   @Input()
   get hasBackdrop() {
@@ -156,6 +162,7 @@ export class ConnectedOverlayDirective implements OnDestroy {
   constructor(
       private _overlay: Overlay,
       private _renderer: Renderer2,
+      private _scrollDispatcher: ScrollDispatcher,
       templateRef: TemplateRef<any>,
       viewContainerRef: ViewContainerRef,
       @Optional() private _dir: Dir) {
@@ -213,6 +220,7 @@ export class ConnectedOverlayDirective implements OnDestroy {
 
     this._position = this._createPositionStrategy() as ConnectedPositionStrategy;
     overlayConfig.positionStrategy = this._position;
+    overlayConfig.scrollStrategy = this.scrollStrategy;
 
     return overlayConfig;
   }

src/lib/core/overlay/overlay-ref.ts

@@ -1,6 +1,7 @@
 import {NgZone} from '@angular/core';
 import {PortalHost, Portal} from '../portal/portal';
 import {OverlayState} from './overlay-state';
+import {ScrollStrategy} from './scroll/scroll-strategy';
 import {Observable} from 'rxjs/Observable';
 import {Subject} from 'rxjs/Subject';
 
@@ -17,7 +18,10 @@ export class OverlayRef implements PortalHost {
       private _portalHost: PortalHost,
       private _pane: HTMLElement,
       private _state: OverlayState,
-      private _ngZone: NgZone) { }
+      private _ngZone: NgZone) {
+
+    this._state.scrollStrategy.attach(this);
+  }
 
   /** The overlay's HTML element */
   get overlayElement(): HTMLElement {
@@ -37,6 +41,7 @@ export class OverlayRef implements PortalHost {
     this.updateSize();
     this.updateDirection();
     this.updatePosition();
+    this._state.scrollStrategy.enable();
 
     // Enable pointer events for the overlay pane element.
     this._togglePointerEvents(true);
@@ -59,6 +64,7 @@ export class OverlayRef implements PortalHost {
     // This is necessary because otherwise the pane element will cover the page and disable
     // pointer events therefore. Depends on the position strategy and the applied pane boundaries.
     this._togglePointerEvents(false);
+    this._state.scrollStrategy.disable();
 
     return this._portalHost.detach();
   }
@@ -73,6 +79,7 @@ export class OverlayRef implements PortalHost {
 
     this.detachBackdrop();
     this._portalHost.dispose();
+    this._state.scrollStrategy.disable();
   }
 
   /**

src/lib/core/overlay/overlay-state.ts

@@ -1,5 +1,7 @@
 import {PositionStrategy} from './position/position-strategy';
 import {LayoutDirection} from '../rtl/dir';
+import {ScrollStrategy} from './scroll/scroll-strategy';
+import {NoopScrollStrategy} from './scroll/noop-scroll-strategy';
 
 
 /**
@@ -10,6 +12,9 @@ export class OverlayState {
   /** Strategy with which to position the overlay. */
   positionStrategy: PositionStrategy;
 
+  /** Strategy to be used when handling scroll events while the overlay is open. */
+  scrollStrategy: ScrollStrategy = new NoopScrollStrategy();
+
   /** Whether the overlay has a backdrop. */
   hasBackdrop: boolean = false;
 

src/lib/core/overlay/overlay.spec.ts

@@ -7,6 +7,7 @@ import {OverlayContainer} from './overlay-container';
 import {OverlayState} from './overlay-state';
 import {PositionStrategy} from './position/position-strategy';
 import {OverlayModule} from './overlay-directives';
+import {ScrollStrategy} from './scroll/scroll-strategy';
 
 
 describe('Overlay', () => {
@@ -295,6 +296,50 @@ describe('Overlay', () => {
     });
 
   });
+
+  describe('scroll strategy', () => {
+    let fakeScrollStrategy: ScrollStrategy;
+    let config: OverlayState;
+
+    beforeEach(() => {
+      config = new OverlayState();
+      fakeScrollStrategy = {
+        attach: jasmine.createSpy('attach spy'),
+        enable: jasmine.createSpy('enable spy'),
+        disable: jasmine.createSpy('disable spy')
+      };
+      config.scrollStrategy = fakeScrollStrategy;
+    });
+
+    it('should attach the overlay ref to the scroll strategy', () => {
+      let overlayRef = overlay.create(config);
+
+      expect(fakeScrollStrategy.attach).toHaveBeenCalledWith(overlayRef);
+    });
+
+    it('should enable the scroll strategy when the overlay is attached', () => {
+      let overlayRef = overlay.create(config);
+
+      overlayRef.attach(componentPortal);
+      expect(fakeScrollStrategy.enable).toHaveBeenCalled();
+    });
+
+    it('should disable the scroll strategy once the overlay is detached', () => {
+      let overlayRef = overlay.create(config);
+
+      overlayRef.attach(componentPortal);
+      overlayRef.detach();
+
+      expect(fakeScrollStrategy.disable).toHaveBeenCalled();
+    });
+
+    it('should disable the scroll strategy when the overlay is destroyed', () => {
+      let overlayRef = overlay.create(config);
+
+      overlayRef.dispose();
+      expect(fakeScrollStrategy.disable).toHaveBeenCalled();
+    });
+  });
 });
 
 describe('OverlayContainer theming', () => {

src/lib/core/overlay/overlay.ts

@@ -30,7 +30,7 @@ let defaultState = new OverlayState();
  *
  * An overlay *is* a PortalHost, so any kind of Portal can be loaded into one.
  */
- @Injectable()
+@Injectable()
 export class Overlay {
   constructor(private _overlayContainer: OverlayContainer,
               private _componentFactoryResolver: ComponentFactoryResolver,

src/lib/core/overlay/scroll/close-scroll-strategy.spec.ts

@@ -0,0 +1,78 @@
+import {inject, TestBed, async} from '@angular/core/testing';
+import {NgModule, Component} from '@angular/core';
+import {Subject} from 'rxjs/Subject';
+import {
+  PortalModule,
+  ComponentPortal,
+  Overlay,
+  OverlayState,
+  OverlayRef,
+  OverlayModule,
+  ScrollStrategy,
+  ScrollDispatcher,
+  CloseScrollStrategy,
+} from '../../core';
+
+
+describe('CloseScrollStrategy', () => {
+  let overlayRef: OverlayRef;
+  let componentPortal: ComponentPortal<MozarellaMsg>;
+  let scrolledSubject = new Subject();
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      imports: [OverlayModule, PortalModule, OverlayTestModule],
+      providers: [
+        {provide: ScrollDispatcher, useFactory: () => {
+          return {scrolled: (delay: number, callback: () => any) => {
+            return scrolledSubject.asObservable().subscribe(callback);
+          }};
+        }}
+      ]
+    });
+
+    TestBed.compileComponents();
+  }));
+
+  beforeEach(inject([Overlay, ScrollDispatcher], (overlay: Overlay,
+    scrollDispatcher: ScrollDispatcher) => {
+
+    let overlayState = new OverlayState();
+    overlayState.scrollStrategy = new CloseScrollStrategy(scrollDispatcher);
+    overlayRef = overlay.create(overlayState);
+    componentPortal = new ComponentPortal(MozarellaMsg);
+  }));
+
+  it('should detach the overlay as soon as the user scrolls', () => {
+    overlayRef.attach(componentPortal);
+    spyOn(overlayRef, 'detach');
+
+    scrolledSubject.next();
+    expect(overlayRef.detach).toHaveBeenCalled();
+  });
+
+  it('should not attempt to detach the overlay after it has been detached', () => {
+    overlayRef.attach(componentPortal);
+    overlayRef.detach();
+
+    spyOn(overlayRef, 'detach');
+    scrolledSubject.next();
+
+    expect(overlayRef.detach).not.toHaveBeenCalled();
+  });
+
+});
+
+
+/** Simple component that we can attach to the overlay. */
+@Component({template: '<p>Mozarella</p>'})
+class MozarellaMsg { }
+
+
+/** Test module to hold the component. */
+@NgModule({
+  imports: [OverlayModule, PortalModule],
+  declarations: [MozarellaMsg],
+  entryComponents: [MozarellaMsg],
+})
+class OverlayTestModule { }

src/lib/core/overlay/scroll/close-scroll-strategy.ts

@@ -0,0 +1,38 @@
+import {ScrollStrategy} from './scroll-strategy';
+import {OverlayRef} from '../overlay-ref';
+import {Subscription} from 'rxjs/Subscription';
+import {ScrollDispatcher} from './scroll-dispatcher';
+
+
+/**
+ * Strategy that will close the overlay as soon as the user starts scrolling.
+ */
+export class CloseScrollStrategy implements ScrollStrategy {
+  private _scrollSubscription: Subscription|null = null;
+  private _overlayRef: OverlayRef;
+
+  constructor(private _scrollDispatcher) { }
+
+  attach(overlayRef: OverlayRef) {
+    this._overlayRef = overlayRef;
+  }
+
+  enable() {
+    if (!this._scrollSubscription) {
+      this._scrollSubscription = this._scrollDispatcher.scrolled(null, () => {
+        if (this._overlayRef.hasAttached()) {
+          this._overlayRef.detach();
+        }
+
+        this.disable();
+      });
+    }
+  }
+
+  disable() {
+    if (this._scrollSubscription) {
+      this._scrollSubscription.unsubscribe();
+      this._scrollSubscription = null;
+    }
+  }
+}

src/lib/core/overlay/scroll/noop-scroll-strategy.ts

@@ -0,0 +1,10 @@
+import {ScrollStrategy} from './scroll-strategy';
+
+/**
+ * Scroll strategy that doesn't do anything.
+ */
+export class NoopScrollStrategy implements ScrollStrategy {
+  enable() { }
+  disable() { }
+  attach() { }
+}