feat(datepicker): popup positioning improvements (#4696)

* feat(datepicker): popup positioning improvements

* Adds fallback positions to the datepicker popup, allowing it to reposition in the cases where it would've gone outside the viewport.
* Fixes an issue that prevented the datepicker from the being positioned properly on the first open due to the calendar not being rendered yet.
* Adds a scroll strategy to reposition the datepicker when the user scrolls away.
* Switches to using `ngSwitch` instead of `ngIf` when determining which view to render.

Fixes #4406.

* chore: unused imports

src/lib/datepicker/calendar.html

@@ -42,9 +42,9 @@
 </div>
 
 <div class="mat-calendar-content" (keydown)="_handleCalendarBodyKeydown($event)"
-     cdkMonitorSubtreeFocus>
+    [ngSwitch]="_monthView" cdkMonitorSubtreeFocus>
   <md-month-view
-      *ngIf="_monthView"
+      *ngSwitchCase="true"
       [activeDate]="_activeDate"
       [selected]="selected"
       [dateFilter]="_dateFilterForViews"
@@ -52,7 +52,7 @@
   </md-month-view>
 
   <md-year-view
-      *ngIf="!_monthView"
+      *ngSwitchDefault
       [activeDate]="_activeDate"
       [selected]="selected"
       [dateFilter]="_dateFilterForViews"

src/lib/datepicker/datepicker.spec.ts

@@ -569,6 +569,82 @@ describe('MdDatepicker', () => {
           .toThrowError(/MdDatepicker: No provider found for .*/);
     });
   });
+
+  describe('popup positioning', () => {
+    let fixture: ComponentFixture<StandardDatepicker>;
+    let testComponent: StandardDatepicker;
+    let input: HTMLElement;
+
+    beforeEach(async(() => {
+      TestBed.configureTestingModule({
+        imports: [MdDatepickerModule, MdInputModule, MdNativeDateModule, NoopAnimationsModule],
+        declarations: [StandardDatepicker],
+      }).compileComponents();
+
+      fixture = TestBed.createComponent(StandardDatepicker);
+      fixture.detectChanges();
+      testComponent = fixture.componentInstance;
+      input = fixture.debugElement.query(By.css('input')).nativeElement;
+      input.style.position = 'fixed';
+    }));
+
+    it('should be below and to the right when there is plenty of space', () => {
+      input.style.top = input.style.left = '20px';
+      testComponent.datepicker.open();
+      fixture.detectChanges();
+
+      const overlayRect = document.querySelector('.cdk-overlay-pane').getBoundingClientRect();
+      const inputRect = input.getBoundingClientRect();
+
+      expect(Math.floor(overlayRect.top))
+          .toBe(Math.floor(inputRect.bottom), 'Expected popup to align to input bottom.');
+      expect(Math.floor(overlayRect.left))
+          .toBe(Math.floor(inputRect.left), 'Expected popup to align to input left.');
+    });
+
+    it('should be above and to the right when there is no space below', () => {
+      input.style.bottom = input.style.left = '20px';
+      testComponent.datepicker.open();
+      fixture.detectChanges();
+
+      const overlayRect = document.querySelector('.cdk-overlay-pane').getBoundingClientRect();
+      const inputRect = input.getBoundingClientRect();
+
+      expect(Math.floor(overlayRect.bottom))
+          .toBe(Math.floor(inputRect.top), 'Expected popup to align to input top.');
+      expect(Math.floor(overlayRect.left))
+          .toBe(Math.floor(inputRect.left), 'Expected popup to align to input left.');
+    });
+
+    it('should be below and to the left when there is no space on the right', () => {
+      input.style.top = input.style.right = '20px';
+      testComponent.datepicker.open();
+      fixture.detectChanges();
+
+      const overlayRect = document.querySelector('.cdk-overlay-pane').getBoundingClientRect();
+      const inputRect = input.getBoundingClientRect();
+
+      expect(Math.floor(overlayRect.top))
+          .toBe(Math.floor(inputRect.bottom), 'Expected popup to align to input bottom.');
+      expect(Math.floor(overlayRect.right))
+          .toBe(Math.floor(inputRect.right), 'Expected popup to align to input right.');
+    });
+
+    it('should be above and to the left when there is no space on the bottom', () => {
+      input.style.bottom = input.style.right = '20px';
+      testComponent.datepicker.open();
+      fixture.detectChanges();
+
+      const overlayRect = document.querySelector('.cdk-overlay-pane').getBoundingClientRect();
+      const inputRect = input.getBoundingClientRect();
+
+      expect(Math.floor(overlayRect.bottom))
+          .toBe(Math.floor(inputRect.top), 'Expected popup to align to input top.');
+      expect(Math.floor(overlayRect.right))
+          .toBe(Math.floor(inputRect.right), 'Expected popup to align to input right.');
+    });
+
+  });
 });
 
 

src/lib/datepicker/datepicker.ts

@@ -10,7 +10,8 @@ import {
   Output,
   ViewChild,
   ViewContainerRef,
-  ViewEncapsulation
+  ViewEncapsulation,
+  NgZone,
 } from '@angular/core';
 import {Overlay} from '../core/overlay/overlay';
 import {OverlayRef} from '../core/overlay/overlay-ref';
@@ -20,18 +21,15 @@ import {Dir} from '../core/rtl/dir';
 import {MdDialog} from '../dialog/dialog';
 import {MdDialogRef} from '../dialog/dialog-ref';
 import {PositionStrategy} from '../core/overlay/position/position-strategy';
-import {
-  OriginConnectionPosition,
-  OverlayConnectionPosition
-} from '../core/overlay/position/connected-position';
+import {RepositionScrollStrategy, ScrollDispatcher} from '../core/overlay/index';
 import {MdDatepickerInput} from './datepicker-input';
-import 'rxjs/add/operator/first';
 import {Subscription} from 'rxjs/Subscription';
 import {MdDialogConfig} from '../dialog/dialog-config';
 import {DateAdapter} from '../core/datetime/index';
 import {createMissingDateImplError} from './datepicker-errors';
 import {ESCAPE} from '../core/keyboard/keycodes';
 import {MdCalendar} from './calendar';
+import 'rxjs/add/operator/first';
 
 
 /** Used to generate a unique ID for each datepicker instance. */
@@ -155,8 +153,11 @@ export class MdDatepicker<D> implements OnDestroy {
 
   private _inputSubscription: Subscription;
 
-  constructor(private _dialog: MdDialog, private _overlay: Overlay,
+  constructor(private _dialog: MdDialog,
+              private _overlay: Overlay,
+              private _ngZone: NgZone,
               private _viewContainerRef: ViewContainerRef,
+              private _scrollDispatcher: ScrollDispatcher,
               @Optional() private _dateAdapter: DateAdapter<D>,
               @Optional() private _dir: Dir) {
     if (!this._dateAdapter) {
@@ -253,6 +254,9 @@ export class MdDatepicker<D> implements OnDestroy {
       let componentRef: ComponentRef<MdDatepickerContent<D>> =
           this._popupRef.attach(this._calendarPortal);
       componentRef.instance.datepicker = this;
+
+      // Update the position once the calendar has rendered.
+      this._ngZone.onStable.first().subscribe(() => this._popupRef.updatePosition());
     }
 
     this._popupRef.backdropClick().first().subscribe(() => this.close());
@@ -265,15 +269,29 @@ export class MdDatepicker<D> implements OnDestroy {
     overlayState.hasBackdrop = true;
     overlayState.backdropClass = 'md-overlay-transparent-backdrop';
     overlayState.direction = this._dir ? this._dir.value : 'ltr';
+    overlayState.scrollStrategy = new RepositionScrollStrategy(this._scrollDispatcher);
 
     this._popupRef = this._overlay.create(overlayState);
   }
 
   /** Create the popup PositionStrategy. */
   private _createPopupPositionStrategy(): PositionStrategy {
-    let origin = {originX: 'start', originY: 'bottom'} as OriginConnectionPosition;
-    let overlay = {overlayX: 'start', overlayY: 'top'} as OverlayConnectionPosition;
-    return this._overlay.position().connectedTo(
-        this._datepickerInput.getPopupConnectionElementRef(), origin, overlay);
+    return this._overlay.position()
+      .connectedTo(this._datepickerInput.getPopupConnectionElementRef(),
+        {originX: 'start', originY: 'bottom'},
+        {overlayX: 'start', overlayY: 'top'}
+      )
+      .withFallbackPosition(
+        { originX: 'start', originY: 'top' },
+        { overlayX: 'start', overlayY: 'bottom' }
+      )
+      .withFallbackPosition(
+        {originX: 'end', originY: 'bottom'},
+        {overlayX: 'end', overlayY: 'top'}
+      )
+      .withFallbackPosition(
+        { originX: 'end', originY: 'top' },
+        { overlayX: 'end', overlayY: 'bottom' }
+      );
   }
 }