fix(core): handle GestureObservers the same as event listeners

packages/core/ui/core/view/index.d.ts

@@ -587,7 +587,7 @@ export abstract class View extends ViewCommon {
  */
  public focus(): boolean;
 
- public getGestureObservers(type: GestureTypes): Array<GesturesObserver>;
+ public getGestureObservers(type: GestureTypes): Array<GesturesObserver> | undefined;
 
  /**
  * Removes listener(s) for the specified event name.

packages/core/ui/core/view/view-common.ts

@@ -278,7 +278,14 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
  }
  }
 
- _observe(type: GestureTypes, callback: (args: GestureEventData) => void, thisArg?: any): void {
+ protected _observe(type: GestureTypes, callback: (args: GestureEventData) => void, thisArg?: any): void {
+ thisArg = thisArg || undefined;
+
+ if (this._gestureObservers[type]?.find((observer) => observer.callback === callback && observer.context === thisArg)) {
+ // Already added.
+ return;
+ }
+
  if (!this._gestureObservers[type]) {
  this._gestureObservers[type] = [];
  }
@@ -291,6 +298,8 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
  }
 
  public addEventListener(eventNames: string, callback: (data: EventData) => void, thisArg?: any) {
+ thisArg = thisArg || undefined;
+
  // Normalize "ontap" -> "tap"
  const normalizedName = getEventOrGestureName(eventNames);
 
@@ -300,14 +309,16 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
 
  // If it's a gesture (and this Observable declares e.g. `static tapEvent`)
  if (gesture && !this._isEvent(normalizedName)) {
- this._observe(gesture, callback as unknown as (data: GestureEventData) => void, thisArg);
+ this._observe(gesture, callback, thisArg);
  return;
  }
 
  super.addEventListener(normalizedName, callback, thisArg);
  }
 
  public removeEventListener(eventNames: string, callback?: (data: EventData) => void, thisArg?: any) {
+ thisArg = thisArg || undefined;
+
  // Normalize "ontap" -> "tap"
  const normalizedName = getEventOrGestureName(eventNames);
 
@@ -317,7 +328,7 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
 
  // If it's a gesture (and this Observable declares e.g. `static tapEvent`)
  if (gesture && !this._isEvent(normalizedName)) {
- this._disconnectGestureObservers(gesture);
+ this._disconnectGestureObservers(gesture, callback, thisArg);
  return;
  }
 
@@ -479,14 +490,34 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
  return this.constructor && `${name}Event` in this.constructor;
  }
 
- private _disconnectGestureObservers(type: GestureTypes): void {
+ private _disconnectGestureObservers(type: GestureTypes, callback?: (data: EventData) => void, thisArg?: any): void {
+ // Largely mirrors the implementation of Observable.innerRemoveEventListener().
+
  const observers = this.getGestureObservers(type);
  if (!observers) {
  return;
  }
 
- for (const observer of observers) {
+ for (let i = 0; i < observers.length; i++) {
+ const observer = observers[i];
+
+ // If we have a `thisArg`, refine on both `callback` and `thisArg`.
+ if (thisArg && (observer.callback !== callback || observer.context !== thisArg)) {
+ continue;
+ }
+
+ // If we don't have a `thisArg`, refine only on `callback`.
+ if (callback && observer.callback !== callback) {
+ continue;
+ }
+
  observer.disconnect();
+ observers.splice(i, 1);
+ i--;
+ }
+
+ if (!observers.length) {
+ delete this._gestureObservers[type];
  }
  }
 

packages/core/ui/gestures/gestures-common.ts

@@ -338,7 +338,7 @@ export function fromString(type: string): GestureTypes | undefined {
 export abstract class GesturesObserverBase implements GesturesObserverDefinition {
  private _callback: (args: GestureEventData) => void;
  private _target: View;
- private _context: any;
+ private _context?: any;
 
  public type: GestureTypes;
 
@@ -354,7 +354,7 @@ export abstract class GesturesObserverBase implements GesturesObserverDefinition
  return this._context;
  }
 
- constructor(target: View, callback: (args: GestureEventData) => void, context: any) {
+ constructor(target: View, callback: (args: GestureEventData) => void, context?: any) {
  this._target = target;
  this._callback = callback;
  this._context = context;
@@ -364,21 +364,6 @@ export abstract class GesturesObserverBase implements GesturesObserverDefinition
  public abstract observe(type: GestureTypes);
 
  public disconnect() {
- // remove gesture observer from map
- if (this.target) {
- const list = this.target.getGestureObservers(this.type);
- if (list && list.length > 0) {
- for (let i = 0; i < list.length; i++) {
- if (list[i].callback === this.callback) {
- break;
- }
- }
- list.length = 0;
-
- this.target._gestureObservers[this.type] = undefined;
- delete this.target._gestureObservers[this.type];
- }
- }
  this._target = null;
  this._callback = null;
  this._context = null;