fix(cdk/testing): simulate offsetX and offsetY in mouse events

We already supported dispatching mouse events at specific element coordinates, but we were using them only to set `clientX` and `clientY`. These changes also set `offsetX` and `offsetY` since they're the native representation of element-relative coordinates.

src/cdk/testing/testbed/fake-events/dispatch-events.ts

@@ -56,10 +56,15 @@ export function dispatchMouseEvent(
   type: string,
   clientX = 0,
   clientY = 0,
+  offsetX?: number,
+  offsetY?: number,
   button?: number,
   modifiers?: ModifierKeys,
 ): MouseEvent {
-  return dispatchEvent(node, createMouseEvent(type, clientX, clientY, button, modifiers));
+  return dispatchEvent(
+    node,
+    createMouseEvent(type, clientX, clientY, offsetX, offsetY, button, modifiers),
+  );
 }
 
 /**
@@ -71,9 +76,14 @@ export function dispatchPointerEvent(
   type: string,
   clientX = 0,
   clientY = 0,
+  offsetX?: number,
+  offsetY?: number,
   options?: PointerEventInit,
 ): PointerEvent {
-  return dispatchEvent(node, createPointerEvent(type, clientX, clientY, options)) as PointerEvent;
+  return dispatchEvent(
+    node,
+    createPointerEvent(type, clientX, clientY, offsetX, offsetY, options),
+  ) as PointerEvent;
 }
 
 /**

src/cdk/testing/testbed/fake-events/event-objects.ts

@@ -19,6 +19,8 @@ export function createMouseEvent(
   type: string,
   clientX = 0,
   clientY = 0,
+  offsetX = 1,
+  offsetY = 1,
   button = 0,
   modifiers: ModifierKeys = {},
 ) {
@@ -50,8 +52,13 @@ export function createMouseEvent(
 
   // The `MouseEvent` constructor doesn't allow us to pass these properties into the constructor.
   // Override them to `1`, because they're used for fake screen reader event detection.
-  defineReadonlyEventProperty(event, 'offsetX', 1);
-  defineReadonlyEventProperty(event, 'offsetY', 1);
+  if (offsetX != null) {
+    defineReadonlyEventProperty(event, 'offsetX', offsetX);
+  }
+
+  if (offsetY != null) {
+    defineReadonlyEventProperty(event, 'offsetY', offsetY);
+  }
 
   return event;
 }
@@ -70,9 +77,11 @@ export function createPointerEvent(
   type: string,
   clientX = 0,
   clientY = 0,
+  offsetX?: number,
+  offsetY?: number,
   options: PointerEventInit = {isPrimary: true},
 ) {
-  return new PointerEvent(type, {
+  const event = new PointerEvent(type, {
     bubbles: true,
     cancelable: true,
     composed: true, // Required for shadow DOM events.
@@ -81,6 +90,16 @@ export function createPointerEvent(
     clientY,
     ...options,
   });
+
+  if (offsetX != null) {
+    defineReadonlyEventProperty(event, 'offsetX', offsetX);
+  }
+
+  if (offsetY != null) {
+    defineReadonlyEventProperty(event, 'offsetY', offsetY);
+  }
+
+  return event;
 }
 
 /**

src/cdk/testing/testbed/unit-test-element.ts

@@ -283,14 +283,19 @@ export class UnitTestElement implements TestElement {
     name: string,
     clientX?: number,
     clientY?: number,
+    offsetX?: number,
+    offsetY?: number,
     button?: number,
   ) {
     // The latest versions of all browsers we support have the new `PointerEvent` API.
     // Though since we capture the two most recent versions of these browsers, we also
     // need to support Safari 12 at time of writing. Safari 12 does not have support for this,
     // so we need to conditionally create and dispatch these events based on feature detection.
     if (typeof PointerEvent !== 'undefined' && PointerEvent) {
-      dispatchPointerEvent(this.element, name, clientX, clientY, {isPrimary: true, button});
+      dispatchPointerEvent(this.element, name, clientX, clientY, offsetX, offsetY, {
+        isPrimary: true,
+        button,
+      });
     }
   }
 
@@ -305,6 +310,8 @@ export class UnitTestElement implements TestElement {
   ) {
     let clientX: number | undefined = undefined;
     let clientY: number | undefined = undefined;
+    let offsetX: number | undefined = undefined;
+    let offsetY: number | undefined = undefined;
     let modifiers: ModifierKeys = {};
 
     if (args.length && typeof args[args.length - 1] === 'object') {
@@ -313,23 +320,57 @@ export class UnitTestElement implements TestElement {
 
     if (args.length) {
       const {left, top, width, height} = await this.getDimensions();
-      const relativeX = args[0] === 'center' ? width / 2 : (args[0] as number);
-      const relativeY = args[0] === 'center' ? height / 2 : (args[1] as number);
+      offsetX = args[0] === 'center' ? width / 2 : (args[0] as number);
+      offsetY = args[0] === 'center' ? height / 2 : (args[1] as number);
 
       // Round the computed click position as decimal pixels are not
       // supported by mouse events and could lead to unexpected results.
-      clientX = Math.round(left + relativeX);
-      clientY = Math.round(top + relativeY);
+      clientX = Math.round(left + offsetX);
+      clientY = Math.round(top + offsetY);
     }
 
-    this._dispatchPointerEventIfSupported('pointerdown', clientX, clientY, button);
-    dispatchMouseEvent(this.element, 'mousedown', clientX, clientY, button, modifiers);
-    this._dispatchPointerEventIfSupported('pointerup', clientX, clientY, button);
-    dispatchMouseEvent(this.element, 'mouseup', clientX, clientY, button, modifiers);
+    this._dispatchPointerEventIfSupported(
+      'pointerdown',
+      clientX,
+      clientY,
+      offsetX,
+      offsetY,
+      button,
+    );
+    dispatchMouseEvent(
+      this.element,
+      'mousedown',
+      clientX,
+      clientY,
+      offsetX,
+      offsetY,
+      button,
+      modifiers,
+    );
+    this._dispatchPointerEventIfSupported('pointerup', clientX, clientY, offsetX, offsetY, button);
+    dispatchMouseEvent(
+      this.element,
+      'mouseup',
+      clientX,
+      clientY,
+      offsetX,
+      offsetY,
+      button,
+      modifiers,
+    );
 
     // If a primary event name is specified, emit it after the mouse event sequence.
     if (primaryEventName !== null) {
-      dispatchMouseEvent(this.element, primaryEventName, clientX, clientY, button, modifiers);
+      dispatchMouseEvent(
+        this.element,
+        primaryEventName,
+        clientX,
+        clientY,
+        offsetX,
+        offsetY,
+        button,
+        modifiers,
+      );
     }
 
     // This call to _stabilize should not be needed since the callers will already do that them-

src/material-experimental/mdc-menu/menu.spec.ts

@@ -431,7 +431,7 @@ describe('MDC-based MatMenu', () => {
     focusMonitor.monitor(triggerEl, false);
 
     // Trigger a fake right click.
-    dispatchEvent(triggerEl, createMouseEvent('mousedown', 50, 100, 2));
+    dispatchEvent(triggerEl, createMouseEvent('mousedown', 50, 100, undefined, undefined, 2));
 
     // A click without a left button mousedown before it is considered a keyboard open.
     triggerEl.click();

src/material-experimental/mdc-tabs/tab-header.spec.ts

@@ -493,7 +493,10 @@ describe('MDC-based MatTabHeader', () => {
       it('should not scroll when pressing the right mouse button', fakeAsync(() => {
         expect(header.scrollDistance).withContext('Expected to start off not scrolled.').toBe(0);
 
-        dispatchEvent(nextButton, createMouseEvent('mousedown', undefined, undefined, 2));
+        dispatchEvent(
+          nextButton,
+          createMouseEvent('mousedown', undefined, undefined, undefined, undefined, 2),
+        );
         fixture.detectChanges();
         tick(3000);
 

src/material/menu/menu.spec.ts

@@ -432,7 +432,7 @@ describe('MatMenu', () => {
     focusMonitor.monitor(triggerEl, false);
 
     // Trigger a fake right click.
-    dispatchEvent(triggerEl, createMouseEvent('mousedown', 50, 100, 2));
+    dispatchEvent(triggerEl, createMouseEvent('mousedown', 50, 100, undefined, undefined, 2));
 
     // A click without a left button mousedown before it is considered a keyboard open.
     triggerEl.click();

src/material/slider/slider.spec.ts

@@ -1778,7 +1778,7 @@ function dispatchMousedownEventSequence(
   const y = dimensions.top + dimensions.height * percentage;
 
   dispatchMouseenterEvent(sliderElement);
-  dispatchEvent(sliderElement, createMouseEvent('mousedown', x, y, button));
+  dispatchEvent(sliderElement, createMouseEvent('mousedown', x, y, undefined, undefined, button));
 }
 
 /**

src/material/tabs/tab-header.spec.ts

@@ -490,7 +490,10 @@ describe('MatTabHeader', () => {
       it('should not scroll when pressing the right mouse button', fakeAsync(() => {
         expect(header.scrollDistance).withContext('Expected to start off not scrolled.').toBe(0);
 
-        dispatchEvent(nextButton, createMouseEvent('mousedown', undefined, undefined, 2));
+        dispatchEvent(
+          nextButton,
+          createMouseEvent('mousedown', undefined, undefined, undefined, undefined, 2),
+        );
         fixture.detectChanges();
         tick(3000);