From 7994a394dc0918dac53ef1835f10dd5c33039a98 Mon Sep 17 00:00:00 2001
From: Forrest Li <forrest.li@kitware.com>
Date: Mon, 12 Jul 2021 10:53:24 -0400
Subject: [PATCH] feat(macro): Support cancelling debounced calls

---
 Sources/interfaces.d.ts | 8 ++++++++
 Sources/macro.d.ts      | 6 ++++--
 Sources/macro.js        | 6 +++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/Sources/interfaces.d.ts b/Sources/interfaces.d.ts
index fed2fb1870b..30260bea9d0 100644
--- a/Sources/interfaces.d.ts
+++ b/Sources/interfaces.d.ts
@@ -16,6 +16,14 @@ export interface vtkRange {
 	max: number;
 }
 
+/**
+ * Represents a debounced function.
+ */
+export interface vtkDebouncedFunction {
+  (...args: any) : any;
+  cancel() : void;
+}
+
 export interface vtkOutputPort {
 	filter: vtkAlgorithm;
 }
diff --git a/Sources/macro.d.ts b/Sources/macro.d.ts
index bc19ec36e8d..29688dad86e 100644
--- a/Sources/macro.d.ts
+++ b/Sources/macro.d.ts
@@ -1,4 +1,4 @@
-import { vtkSubscription, vtkProperty, vtkPropertyDomain } from "./interfaces";
+import { vtkSubscription, vtkDebouncedFunction, vtkProperty, vtkPropertyDomain } from "./interfaces";
 
 /**
  * Allow user to redefine vtkXXXMacro method call.
@@ -305,8 +305,10 @@ export function traverseInstanceTree(
  * @param func
  * @param wait
  * @param immediate (default false)
+ * @returns vtkDebouncedFunction A debounced function that can be called.
+ *          Use .cancel() to clear any pending debounced call.
  */
-export function debounce(func: (...args: any) => any, wait: number, immediate?: boolean): (...args: any) => any;
+export function debounce(func: (...args: any) => any, wait: number, immediate?: boolean): vtkDebouncedFunction;
 
 /**
  * Creates a throttled function that only invokes `func` at most once per
diff --git a/Sources/macro.js b/Sources/macro.js
index fd797061e74..655d12e4c76 100644
--- a/Sources/macro.js
+++ b/Sources/macro.js
@@ -985,7 +985,7 @@ export function traverseInstanceTree(
 
 export function debounce(func, wait, immediate) {
   let timeout;
-  return (...args) => {
+  const debounced = (...args) => {
     const context = this;
     const later = () => {
       timeout = null;
@@ -1000,6 +1000,10 @@ export function debounce(func, wait, immediate) {
       func.apply(context, args);
     }
   };
+
+  debounced.cancel = () => clearTimeout(timeout);
+
+  return debounced;
 }
 
 // ----------------------------------------------------------------------------