fix(overlay): CdkConnectedOverlay ignoring offset from position config (#10451)

Author: crisbeto

src/cdk/overlay/overlay-directives.spec.ts

@@ -333,6 +333,32 @@ describe('Overlay directives', () => {
       expect(Math.floor(triggerRect.bottom)).toBe(Math.floor(overlayRect.top));
     });
 
+    it('should take the offset from the position', () => {
+      const trigger = fixture.nativeElement.querySelector('#trigger');
+
+      trigger.style.position = 'fixed';
+      trigger.style.top = '200px';
+      trigger.style.left = '200px';
+
+      fixture.componentInstance.positionOverrides = [{
+        originX: 'start',
+        originY: 'top',
+        overlayX: 'start',
+        overlayY: 'top',
+        offsetX: 20,
+        offsetY: 10
+      }];
+
+      fixture.componentInstance.isOpen = true;
+      fixture.detectChanges();
+
+      const triggerRect = trigger.getBoundingClientRect();
+      const overlayRect = getPaneElement().getBoundingClientRect();
+
+      expect(Math.floor(overlayRect.top)).toBe(Math.floor(triggerRect.top) + 10);
+      expect(Math.floor(overlayRect.left)).toBe(Math.floor(triggerRect.left) + 20);
+    });
+
   });
 
   describe('outputs', () => {
@@ -418,8 +444,8 @@ class ConnectedOverlayDirectiveTest {
   height: number | string;
   minWidth: number | string;
   minHeight: number | string;
-  offsetX = 0;
-  offsetY = 0;
+  offsetX: number;
+  offsetY: number;
   triggerOverride: CdkOverlayOrigin;
   hasBackdrop: boolean;
   backdropClickHandler = jasmine.createSpy('backdropClick handler');

src/cdk/overlay/overlay-directives.ts

@@ -115,8 +115,8 @@ export class CdkConnectedOverlay implements OnDestroy, OnChanges {
   private _hasBackdrop = false;
   private _lockPosition = false;
   private _backdropSubscription = Subscription.EMPTY;
-  private _offsetX: number = 0;
-  private _offsetY: number = 0;
+  private _offsetX: number;
+  private _offsetY: number;
   private _position: FlexibleConnectedPositionStrategy;
 
   /** Origin for the connected overlay. */
@@ -311,8 +311,8 @@ export class CdkConnectedOverlay implements OnDestroy, OnChanges {
       originY: pos.originY,
       overlayX: pos.overlayX,
       overlayY: pos.overlayY,
-      offsetX: this.offsetX,
-      offsetY: this.offsetY
+      offsetX: pos.offsetX || this.offsetX,
+      offsetY: pos.offsetY || this.offsetY
     }));
 
     positionStrategy.withPositions(positions);