fix(menu): reposition menu if it would open off screen

src/lib/menu/menu-trigger.ts

@@ -20,7 +20,9 @@ import {
     TemplatePortal,
     ConnectedPositionStrategy,
     HorizontalConnectionPos,
-    VerticalConnectionPos
+    VerticalConnectionPos,
+    OriginConnectionPosition,
+    OverlayConnectionPosition
 } from '../core';
 import { Subscription } from 'rxjs/Subscription';
 
@@ -181,14 +183,33 @@ export class MdMenuTrigger implements AfterViewInit, OnDestroy {
    * @returns ConnectedPositionStrategy
    */
   private _getPosition(): ConnectedPositionStrategy  {
-    const positionX: HorizontalConnectionPos = this.menu.positionX === 'before' ? 'end' : 'start';
-    const positionY: VerticalConnectionPos = this.menu.positionY === 'above' ? 'bottom' : 'top';
-
-    return this._overlay.position().connectedTo(
-      this._element,
-      {originX: positionX, originY: positionY},
-      {overlayX: positionX, overlayY: positionY}
-    );
+    const [posX, fallbackX]: HorizontalConnectionPos[] =
+      this.menu.positionX === 'before' ? ['end', 'start'] : ['start', 'end'];
+
+    const [posY, fallbackY]: VerticalConnectionPos[] =
+      this.menu.positionY === 'above' ? ['bottom', 'top'] : ['top', 'bottom'];
+
+    return this._overlay.position()
+      .connectedTo(this._element, this._originPos(posX, posY), this._overlayPos(posX, posY))
+      .withFallbackPosition(
+        this._originPos(fallbackX, posY), this._overlayPos(fallbackX, posY))
+      .withFallbackPosition(
+        this._originPos(posX, fallbackY), this._overlayPos(posX, fallbackY))
+      .withFallbackPosition(
+        this._originPos(fallbackX, fallbackY), this._overlayPos(fallbackX, fallbackY));
+  }
+
+
+  /**  Converts the designated point into an OriginConnectionPosition. */
+  private _originPos(x: HorizontalConnectionPos,
+                     y: VerticalConnectionPos): OriginConnectionPosition {
+    return {originX: x, originY: y} as OriginConnectionPosition;
+  }
+
+  /**  Converts the designated point into an OverlayConnectionPosition. */
+  private _overlayPos(x: HorizontalConnectionPos,
+                      y: VerticalConnectionPos): OverlayConnectionPosition {
+    return {overlayX: x, overlayY: y} as OverlayConnectionPosition;
   }
 
   // TODO: internal

src/lib/menu/menu.spec.ts

@@ -2,6 +2,7 @@ import {TestBed, async} from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
 import {
   Component,
+  ElementRef,
   EventEmitter,
   Output,
   TemplateRef,
@@ -15,6 +16,7 @@ import {
   MenuPositionY
 } from './menu';
 import {OverlayContainer} from '../core/overlay/overlay-container';
+import {ViewportRuler} from '../core/overlay/position/viewport-ruler';
 
 describe('MdMenu', () => {
   let overlayContainerElement: HTMLElement;
@@ -26,14 +28,23 @@ describe('MdMenu', () => {
       providers: [
         {provide: OverlayContainer, useFactory: () => {
           overlayContainerElement = document.createElement('div');
+          overlayContainerElement.style.position = 'fixed';
+          overlayContainerElement.style.top = '0';
+          overlayContainerElement.style.left = '0';
+          document.body.appendChild(overlayContainerElement);
           return {getContainerElement: () => overlayContainerElement};
-        }}
+        }},
+        {provide: ViewportRuler, useClass: FakeViewportRuler}
       ]
     });
 
     TestBed.compileComponents();
   }));
 
+  afterEach(() => {
+    document.body.removeChild(overlayContainerElement);
+  });
+
   it('should open the menu as an idempotent operation', () => {
     const fixture = TestBed.createComponent(SimpleMenu);
     fixture.detectChanges();
@@ -42,8 +53,8 @@ describe('MdMenu', () => {
       fixture.componentInstance.trigger.openMenu();
       fixture.componentInstance.trigger.openMenu();
 
-      expect(overlayContainerElement.textContent).toContain('Simple Content');
-      expect(overlayContainerElement.textContent).toContain('Disabled Content');
+      expect(overlayContainerElement.textContent).toContain('Item');
+      expect(overlayContainerElement.textContent).toContain('Disabled');
     }).not.toThrowError();
   });
 
@@ -110,6 +121,123 @@ describe('MdMenu', () => {
       expect(panel.classList).not.toContain('md-menu-below');
     });
 
+    describe('fallback positions', () => {
+
+      it('should fall back to "before" mode if "after" mode would not fit on screen', () => {
+        const fixture = TestBed.createComponent(SimpleMenu);
+        fixture.detectChanges();
+        const trigger = fixture.componentInstance.triggerEl.nativeElement;
+
+        // Push trigger to the right side of viewport, so it doesn't have space to open
+        // in its default "after" position on the right side.
+        trigger.style.position = 'relative';
+        trigger.style.left = '900px';
+
+        fixture.componentInstance.trigger.openMenu();
+        fixture.detectChanges();
+        const overlayPane = overlayContainerElement.children[0] as HTMLElement;
+        const triggerRect = trigger.getBoundingClientRect();
+        const overlayRect = overlayPane.getBoundingClientRect();
+
+        // In "before" position, the right sides of the overlay and the origin are aligned.
+        // To find the overlay left, subtract the menu width from the origin's right side.
+        const expectedLeft = triggerRect.right - overlayRect.width;
+        expect(overlayRect.left.toFixed(2))
+          .toEqual(expectedLeft.toFixed(2),
+            `Expected menu to open in "before" position if "after" position wouldn't fit.`);
+
+        // The y-position of the overlay should be unaffected, as it can already fit vertically
+        expect(overlayRect.top.toFixed(2))
+          .toEqual(triggerRect.top.toFixed(2),
+            `Expected menu top position to be unchanged if it can fit in the viewport.`);
+      });
+
+      it('should fall back to "above" mode if "below" mode would not fit on screen', () => {
+        const fixture = TestBed.createComponent(SimpleMenu);
+        fixture.detectChanges();
+        const trigger = fixture.componentInstance.triggerEl.nativeElement;
+
+        // Push trigger to the bottom part of viewport, so it doesn't have space to open
+        // in its default "below" position below the trigger.
+        trigger.style.position = 'relative';
+        trigger.style.top = '600px';
+
+        fixture.componentInstance.trigger.openMenu();
+        fixture.detectChanges();
+        const overlayPane = overlayContainerElement.children[0] as HTMLElement;
+        const triggerRect = trigger.getBoundingClientRect();
+        const overlayRect = overlayPane.getBoundingClientRect();
+
+        // In "above" position, the bottom edges of the overlay and the origin are aligned.
+        // To find the overlay top, subtract the menu height from the origin's bottom edge.
+        const expectedTop = triggerRect.bottom - overlayRect.height;
+        expect(overlayRect.top.toFixed(2))
+          .toEqual(expectedTop.toFixed(2),
+            `Expected menu to open in "above" position if "below" position wouldn't fit.`);
+
+        // The x-position of the overlay should be unaffected, as it can already fit horizontally
+        expect(overlayRect.left.toFixed(2))
+          .toEqual(triggerRect.left.toFixed(2),
+            `Expected menu x position to be unchanged if it can fit in the viewport.`);
+      });
+
+      it('should re-position menu on both axes if both defaults would not fit', () => {
+        const fixture = TestBed.createComponent(SimpleMenu);
+        fixture.detectChanges();
+        const trigger = fixture.componentInstance.triggerEl.nativeElement;
+
+        // push trigger to the bottom, right part of viewport, so it doesn't have space to open
+        // in its default "after below" position.
+        trigger.style.position = 'relative';
+        trigger.style.left = '900px';
+        trigger.style.top = '600px';
+
+        fixture.componentInstance.trigger.openMenu();
+        fixture.detectChanges();
+        const overlayPane = overlayContainerElement.children[0] as HTMLElement;
+        const triggerRect = trigger.getBoundingClientRect();
+        const overlayRect = overlayPane.getBoundingClientRect();
+
+        const expectedLeft = triggerRect.right - overlayRect.width;
+        const expectedTop = triggerRect.bottom - overlayRect.height;
+
+        expect(overlayRect.left.toFixed(2))
+          .toEqual(expectedLeft.toFixed(2),
+            `Expected menu to open in "before" position if "after" position wouldn't fit.`);
+
+        expect(overlayRect.top.toFixed(2))
+          .toEqual(expectedTop.toFixed(2),
+            `Expected menu to open in "above" position if "below" position wouldn't fit.`);
+      });
+
+      it('should re-position a menu with custom position set', () => {
+        const fixture = TestBed.createComponent(PositionedMenu);
+        fixture.detectChanges();
+        const trigger = fixture.componentInstance.triggerEl.nativeElement;
+
+        fixture.componentInstance.trigger.openMenu();
+        fixture.detectChanges();
+        const overlayPane = overlayContainerElement.children[0] as HTMLElement;
+        const triggerRect = trigger.getBoundingClientRect();
+        const overlayRect = overlayPane.getBoundingClientRect();
+
+        // As designated "before" position won't fit on screen, the menu should fall back
+        // to "after" mode, where the left sides of the overlay and trigger are aligned.
+        expect(overlayRect.left.toFixed(2))
+          .toEqual(triggerRect.left.toFixed(2),
+            `Expected menu to open in "after" position if "before" position wouldn't fit.`);
+
+        // As designated "above" position won't fit on screen, the menu should fall back
+        // to "below" mode, where the top edges of the overlay and trigger are aligned.
+        expect(overlayRect.top.toFixed(2))
+          .toEqual(triggerRect.top.toFixed(2),
+            `Expected menu to open in "below" position if "above" position wouldn't fit.`);
+      });
+
+    });
+
+
+
   });
 
   describe('animations', () => {
@@ -142,27 +270,29 @@ describe('MdMenu', () => {
 
 @Component({
   template: `
-    <button [md-menu-trigger-for]="menu">Toggle menu</button>
+    <button [md-menu-trigger-for]="menu" #triggerEl>Toggle menu</button>
     <md-menu #menu="mdMenu">
-      <button md-menu-item> Simple Content </button>
-      <button md-menu-item disabled> Disabled Content </button>
+      <button md-menu-item> Item </button>
+      <button md-menu-item disabled> Disabled </button>
     </md-menu>
   `
 })
 class SimpleMenu {
   @ViewChild(MdMenuTrigger) trigger: MdMenuTrigger;
+  @ViewChild('triggerEl') triggerEl: ElementRef;
 }
 
 @Component({
   template: `
-    <button [md-menu-trigger-for]="menu">Toggle menu</button>
+    <button [md-menu-trigger-for]="menu" #triggerEl>Toggle menu</button>
     <md-menu x-position="before" y-position="above" #menu="mdMenu">
       <button md-menu-item> Positioned Content </button>
     </md-menu>
   `
 })
 class PositionedMenu {
   @ViewChild(MdMenuTrigger) trigger: MdMenuTrigger;
+  @ViewChild('triggerEl') triggerEl: ElementRef;
 }
 
 
@@ -195,3 +325,14 @@ class CustomMenuPanel implements MdMenuPanel {
 class CustomMenu {
   @ViewChild(MdMenuTrigger) trigger: MdMenuTrigger;
 }
+
+class FakeViewportRuler {
+  getViewportRect() {
+    return {
+      left: 0, top: 0, width: 1014, height: 686, bottom: 686, right: 1014
+    };
+  }
+  getViewportScrollPosition() {
+    return {top: 0, left: 0};
+  }
+}