fix(ui): Event bus method types (fix: #15759) (#15765)

* fix(ui): Make off method optional again

* fix(ui): Fix naming in docs

* feat(ui): Improve ctx type of EventBus

* Update event-bus-util.md

---------

Co-authored-by: Yusuf Kandemir <yusuf.kandemir@outlook.com.tr>
Co-authored-by: Razvan Stoenescu <razvan.stoenescu@gmail.com>

docs/src/pages/quasar-utils/event-bus-util.md

@@ -32,7 +32,7 @@ bus.on('some-event', (arg1, arg2, arg3) => {
 bus.emit('some-event', 'arg1 value', 'arg2 value', 'arg3 value')
 ```
 
-If using Typescript, then events can also be typed strictly:
+When using TypeScript the events can be strongly-typed:
 
 ```js
 // Quasar v2.11.11+

ui/types/utils.d.ts

@@ -107,11 +107,23 @@ interface Callbacks {
   [key: string]: (...args: any[]) => void;
 }
 
-export class EventBus<T extends Callbacks> {
-  on<K extends keyof T>(event: K, callback: T[K], ctx?: any): this;
-  once<K extends keyof T>(event: K, callback: T[K], ctx?: any): this;
+export class EventBus<T extends Callbacks = Callbacks> {
+  on<K extends keyof T>(
+    event: K,
+    callback: T[K],
+    ...ctx: unknown extends ThisParameterType<T[K]>
+      ? []
+      : [ctx: ThisParameterType<T[K]>]
+  ): this;
+  once<K extends keyof T>(
+    event: K,
+    callback: T[K],
+    ...ctx: unknown extends ThisParameterType<T[K]>
+      ? []
+      : [ctx: ThisParameterType<T[K]>]
+  ): this;
   emit<K extends keyof T>(event: K, ...args: Parameters<T[K]>): this;
-  off<K extends keyof T>(event: K, callback: T[K]): this;
+  off<K extends keyof T>(event: K, callback?: T[K]): this;
 }
 
 interface CreateMetaMixinContext extends ComponentPublicInstance {