fix(select): prevent the panel from going outside the viewport horizontally

Prevents the select panel from going outside the viewport along the x axis.

Fixes angular#3504.
Fixes angular#3831.

Author: crisbeto

src/lib/select/select.html

@@ -15,7 +15,7 @@
 
 <ng-template cdk-connected-overlay [origin]="origin" [open]="panelOpen" hasBackdrop (backdropClick)="close()"
   backdropClass="cdk-overlay-transparent-backdrop" [positions]="_positions" [minWidth]="_triggerWidth"
-  [offsetY]="_offsetY" [offsetX]="_offsetX" (attach)="_setScrollTop()">
+  [offsetY]="_offsetY" (attach)="_onAttached()">
   <div class="mat-select-panel" [@transformPanel]="'showing'" (@transformPanel.done)="_onPanelDone()"
     (keydown)="_keyManager.onKeydown($event)" [style.transformOrigin]="_transformOrigin"
       [class.mat-select-panel-done-animating]="_panelDoneAnimating">

src/lib/select/select.scss

@@ -125,6 +125,7 @@ $mat-select-trigger-font-size: 16px !default;
   padding-top: 0;
   padding-bottom: 0;
   max-height: $mat-select-panel-max-height;
+  min-width: 100%; // prevents some animation twitching and test inconsistencies in IE11
 
   @include cdk-high-contrast {
     outline: solid 1px;

src/lib/select/select.spec.ts

@@ -12,7 +12,12 @@ import {
 import {NoopAnimationsModule} from '@angular/platform-browser/animations';
 import {MdSelectModule} from './index';
 import {OverlayContainer} from '../core/overlay/overlay-container';
-import {MdSelect, MdSelectFloatPlaceholderType} from './select';
+import {
+  MdSelect,
+  MdSelectFloatPlaceholderType,
+  SELECT_PANEL_EXTRA_WIDTH,
+  SELECT_PANEL_VIEWPORT_PADDING,
+} from './select';
 import {MdSelectDynamicMultipleError, MdSelectNonArrayValueError} from './select-errors';
 import {MdOption} from '../core/option/option';
 import {Dir} from '../core/rtl/dir';
@@ -24,9 +29,22 @@ import {dispatchFakeEvent} from '../core/testing/dispatch-events';
 import {wrappedErrorMessage} from '../core/testing/wrapped-error-message';
 
 
-describe('MdSelect', () => {
+class FakeViewportRuler {
+  getViewportRect() {
+    return {
+      left: 0, top: 0, width: 1014, height: 686, bottom: 686, right: 1014
+    };
+  }
+
+  getViewportScrollPosition() {
+    return {top: 0, left: 0};
+  }
+}
+
+fdescribe('MdSelect', () => {
   let overlayContainerElement: HTMLElement;
   let dir: {value: 'ltr'|'rtl'};
+  let fakeViewportRuler = new FakeViewportRuler();
 
   beforeEach(async(() => {
     TestBed.configureTestingModule({
@@ -65,7 +83,7 @@ describe('MdSelect', () => {
         {provide: Dir, useFactory: () => {
           return dir = { value: 'ltr' };
         }},
-        {provide: ViewportRuler, useClass: FakeViewportRuler}
+        {provide: ViewportRuler, useValue: fakeViewportRuler}
       ]
     });
 
@@ -882,6 +900,97 @@ describe('MdSelect', () => {
 
     });
 
+    describe('limited space to open horizontally', () => {
+      beforeEach(() => {
+        select.style.position = 'absolute';
+        select.style.top = '200px';
+      });
+
+      it('should stay within the viewport when overflowing on the left in ltr', async(() => {
+        select.style.left = '-75px';
+        trigger.click();
+        fixture.detectChanges();
+
+        fixture.whenStable().then(() => {
+          const panelLeft = document.querySelector('.mat-select-panel')
+              .getBoundingClientRect().left;
+          expect(Math.round(panelLeft)).toBe(SELECT_PANEL_VIEWPORT_PADDING,
+              `Expected select panel to be inside the viewport in ltr.`);
+        });
+      }));
+
+      it('should stay within the viewport when overflowing on the right in rtl', async(() => {
+        dir.value = 'rtl';
+        select.style.left = '-75px';
+        trigger.click();
+        fixture.detectChanges();
+
+        fixture.whenStable().then(() => {
+          const panelLeft = document.querySelector('.mat-select-panel')
+              .getBoundingClientRect().left;
+          const targetLeft = SELECT_PANEL_VIEWPORT_PADDING + SELECT_PANEL_EXTRA_WIDTH;
+
+          expect(Math.round(panelLeft)).toBe(targetLeft,
+              `Expected select panel to be inside the viewport in rtl.`);
+        });
+      }));
+
+      it('should stay within the viewport when overflowing on the right in ltr', async(() => {
+        select.style.right = '-75px';
+        trigger.click();
+        fixture.detectChanges();
+
+        fixture.whenStable().then(() => {
+          const viewportRect = fakeViewportRuler.getViewportRect().right;
+          const panelRight = document.querySelector('.mat-select-panel')
+              .getBoundingClientRect().right;
+          const targetRight = SELECT_PANEL_VIEWPORT_PADDING + SELECT_PANEL_EXTRA_WIDTH;
+
+          expect(viewportRect - Math.round(panelRight)).toBe(targetRight,
+              `Expected select panel to be inside the viewport in ltr.`);
+        });
+      }));
+
+      it('should stay within the viewport when overflowing on the right in rtl', async(() => {
+        dir.value = 'rtl';
+        select.style.right = '-75px';
+        trigger.click();
+        fixture.detectChanges();
+
+        fixture.whenStable().then(() => {
+          const viewportRect = fakeViewportRuler.getViewportRect().right;
+          const panelRight = document.querySelector('.mat-select-panel')
+              .getBoundingClientRect().right;
+
+          expect(viewportRect - Math.round(panelRight)).toBe(SELECT_PANEL_VIEWPORT_PADDING,
+              `Expected select panel to be inside the viewport in rtl.`);
+        });
+      }));
+
+      it('should keep the position within the viewport on repeat openings', async(() => {
+        select.style.left = '-75px';
+        trigger.click();
+        fixture.detectChanges();
+
+        let panelLeft = document.querySelector('.mat-select-panel').getBoundingClientRect().left;
+
+        expect(Math.round(panelLeft)).toBe(SELECT_PANEL_VIEWPORT_PADDING,
+            `Expected select panel to be inside the viewport.`);
+
+        fixture.componentInstance.select.close();
+        fixture.detectChanges();
+
+        fixture.whenStable().then(() => {
+          trigger.click();
+          fixture.detectChanges();
+          panelLeft = document.querySelector('.mat-select-panel').getBoundingClientRect().left;
+
+          expect(Math.round(panelLeft)).toBe(SELECT_PANEL_VIEWPORT_PADDING,
+              `Expected select panel continue being inside the viewport.`);
+        });
+      }));
+    });
+
     describe('when scrolled', () => {
 
       // Need to set the scrollTop two different ways to support
@@ -1030,8 +1139,8 @@ describe('MdSelect', () => {
         trigger = multiFixture.debugElement.query(By.css('.mat-select-trigger')).nativeElement;
         select = multiFixture.debugElement.query(By.css('md-select')).nativeElement;
 
-        select.style.marginLeft = '20px';
-        select.style.marginRight = '20px';
+        select.style.marginLeft = '50px';
+        select.style.marginRight = '50px';
       });
 
       it('should adjust for the checkbox in ltr', () => {
@@ -1956,16 +2065,3 @@ class SelectWithPlainTabindex { }
   `
 })
 class SelectEarlyAccessSibling { }
-
-
-class FakeViewportRuler {
-  getViewportRect() {
-    return {
-      left: 0, top: 0, width: 1014, height: 686, bottom: 686, right: 1014
-    };
-  }
-
-  getViewportScrollPosition() {
-    return {top: 0, left: 0};
-  }
-}

src/lib/select/select.ts

@@ -85,6 +85,9 @@ export const SELECT_PANEL_PADDING_Y = 16;
  */
 export const SELECT_PANEL_VIEWPORT_PADDING = 8;
 
+/** Extra width that gets added the to select panel during the open animation. */
+export const SELECT_PANEL_EXTRA_WIDTH = 32;
+
 /** Change event object that is emitted when the select value has changed. */
 export class MdSelectChange {
   constructor(public source: MdSelect, public value: any) { }
@@ -187,13 +190,6 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
   /** Whether the panel's animation is done. */
   _panelDoneAnimating: boolean = false;
 
-  /**
-   * The x-offset of the overlay panel in relation to the trigger's top start corner.
-   * This must be adjusted to align the selected option text over the trigger text when
-   * the panel opens. Will change based on LTR or RTL text direction.
-   */
-  _offsetX = 0;
-
   /**
    * The y-offset of the overlay panel in relation to the trigger's top start corner.
    * This must be adjusted to align the selected option text over the trigger text.
@@ -468,6 +464,7 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
     } else {
       this.onClose.emit();
       this._panelDoneAnimating = false;
+      this.overlayDir.offsetX = 0;
     }
   }
 
@@ -489,12 +486,20 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
     }
   }
 
+  /**
+   * Callback that is invoked when the overlay panel has been attached.
+   */
+  _onAttached(): void {
+    this._calculateOverlayXOffset();
+    this._setScrollTop();
+  }
+
   /**
    * Sets the scroll position of the scroll container. This must be called after
    * the overlay pane is attached or the scroll container element will not yet be
    * present in the DOM.
    */
-  _setScrollTop(): void {
+  private _setScrollTop(): void {
     const scrollContainer =
         this.overlayDir.overlayRef.overlayElement.querySelector('.mat-select-panel');
     scrollContainer.scrollTop = this._scrollTop;
@@ -693,12 +698,6 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
 
   /** Calculates the scroll position and x- and y-offsets of the overlay panel. */
   private _calculateOverlayPosition(): void {
-    this._offsetX = this.multiple ? SELECT_MULTIPLE_PANEL_PADDING_X : SELECT_PANEL_PADDING_X;
-
-    if (!this._isRtl()) {
-      this._offsetX *= -1;
-    }
-
     const panelHeight =
         Math.min(this.options.length * SELECT_OPTION_HEIGHT, SELECT_PANEL_MAX_HEIGHT);
     const scrollContainerHeight = this.options.length * SELECT_OPTION_HEIGHT;
@@ -712,7 +711,7 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
       // center of the overlay panel rather than the top.
       const scrollBuffer = panelHeight / 2;
       this._scrollTop = this._calculateOverlayScroll(selectedIndex, scrollBuffer, maxScroll);
-      this._offsetY = this._calculateOverlayOffset(selectedIndex, scrollBuffer, maxScroll);
+      this._offsetY = this._calculateOverlayYOffset(selectedIndex, scrollBuffer, maxScroll);
     } else {
       // If no option is selected, the panel centers on the first option. In this case,
       // we must only adjust for the height difference between the option element
@@ -774,12 +773,45 @@ export class MdSelect implements AfterContentInit, OnDestroy, OnInit, ControlVal
     return this.ariaLabelledby ? null : this.ariaLabel || this.placeholder;
   }
 
+  /**
+   * Sets the x-offset of the overlay panel in relation to the trigger's top start corner.
+   * This must be adjusted to align the selected option text over the trigger text when
+   * the panel opens. Will change based on LTR or RTL text direction. Note that the offset
+   * can't be calculated until the panel has been attached, because we need to know the
+   * content width in order to constrain the panel within the viewport.
+   */
+  private _calculateOverlayXOffset(): void {
+    let overlayRect = this.overlayDir.overlayRef.overlayElement.getBoundingClientRect();
+    let viewportRect = this._viewportRuler.getViewportRect();
+    let offsetX = this.multiple ? SELECT_MULTIPLE_PANEL_PADDING_X : SELECT_PANEL_PADDING_X;
+    let isRtl = this._isRtl();
+
+    if (!isRtl) {
+      offsetX *= -1;
+    }
+
+    let leftOverflow = 0 - (overlayRect.left + offsetX - (isRtl ? SELECT_PANEL_EXTRA_WIDTH : 0));
+    let rightOverflow = overlayRect.right + offsetX - viewportRect.width
+        + (isRtl ? 0 : SELECT_PANEL_EXTRA_WIDTH);
+
+    if (leftOverflow > 0) {
+      offsetX += leftOverflow + SELECT_PANEL_VIEWPORT_PADDING;
+    } else if (rightOverflow > 0) {
+      offsetX -= rightOverflow + SELECT_PANEL_VIEWPORT_PADDING;
+    }
+
+    // Set the offset directly in order to avoid having to go through change detection and
+    // potentially triggering "changed after it was checked" errors.
+    this.overlayDir.offsetX = offsetX;
+    this.overlayDir.overlayRef.updatePosition();
+  }
+
   /**
    * Calculates the y-offset of the select's overlay panel in relation to the
    * top start corner of the trigger. It has to be adjusted in order for the
    * selected option to be aligned over the trigger when the panel opens.
    */
-  private _calculateOverlayOffset(selectedIndex: number, scrollBuffer: number,
+  private _calculateOverlayYOffset(selectedIndex: number, scrollBuffer: number,
                                   maxScroll: number): number {
     let optionOffsetFromPanelTop: number;