fix(overlay): prevent blurry connected overlays (#1784)

e2e/components/menu/menu-page.ts

@@ -53,8 +53,10 @@ export class MenuPage {
 
   expectMenuLocation(el: ElementFinder, {x,y}: {x: number, y: number}) {
     el.getLocation().then((loc) => {
-      expect(loc.x).toEqual(x);
-      expect(loc.y).toEqual(y);
+      // Round the values because we expect the menu overlay to also have been rounded
+      // to avoid blurriness due to subpixel rendering.
+      expect(loc.x).toEqual(Math.round(x));
+      expect(loc.y).toEqual(Math.round(y));
     });
   }
 

src/lib/core/overlay/position/connected-position-strategy.ts

@@ -227,8 +227,9 @@ export class ConnectedPositionStrategy implements PositionStrategy {
    * @param overlayPoint
    */
   private _setElementPosition(element: HTMLElement, overlayPoint: Point) {
-    let x = overlayPoint.x;
-    let y = overlayPoint.y;
+    // Round the values to prevent blurry overlays due to subpixel rendering.
+    let x = Math.round(overlayPoint.x);
+    let y = Math.round(overlayPoint.y);
 
     // TODO(jelbourn): we don't want to always overwrite the transform property here,
     // because it will need to be used for animations.

src/lib/menu/menu.spec.ts

@@ -155,13 +155,13 @@ describe('MdMenu', () => {
       // 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),
+      expect(overlayRect.left)
+          .toBe(Math.round(expectedLeft),
               `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),
+      expect(overlayRect.top)
+          .toBe(Math.round(triggerRect.top),
               `Expected menu top position to be unchanged if it can fit in the viewport.`);
     });
 
@@ -184,13 +184,13 @@ describe('MdMenu', () => {
       // 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),
+      expect(overlayRect.top)
+          .toBe(Math.round(expectedTop),
               `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),
+      expect(overlayRect.left)
+          .toBe(Math.round(triggerRect.left),
               `Expected menu x position to be unchanged if it can fit in the viewport.`);
     });
 
@@ -214,12 +214,12 @@ describe('MdMenu', () => {
       const expectedLeft = triggerRect.right - overlayRect.width;
       const expectedTop = triggerRect.bottom - overlayRect.height;
 
-      expect(overlayRect.left.toFixed(2))
-          .toEqual(expectedLeft.toFixed(2),
+      expect(overlayRect.left)
+          .toBe(Math.round(expectedLeft),
               `Expected menu to open in "before" position if "after" position wouldn't fit.`);
 
-      expect(overlayRect.top.toFixed(2))
-          .toEqual(expectedTop.toFixed(2),
+      expect(overlayRect.top)
+          .toBe(Math.round(expectedTop),
               `Expected menu to open in "above" position if "below" position wouldn't fit.`);
     });
 
@@ -236,14 +236,14 @@ describe('MdMenu', () => {
 
       // 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),
+      expect(overlayRect.left)
+          .toBe(Math.round(triggerRect.left),
               `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),
+      expect(overlayRect.top)
+          .toBe(Math.round(triggerRect.top),
               `Expected menu to open in "below" position if "above" position wouldn't fit.`);
     });