Create Debouncer; use it for HatAllocator (#1646)

- Required by #1651

## Checklist

- [ ] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [ ] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [ ] I have not broken the cheatsheet

Author: pokey

packages/cursorless-engine/src/core/Debouncer.ts

@@ -0,0 +1,37 @@
+import { ide } from "../singletons/ide.singleton";
+
+/**
+ * Debounces a callback.  Uses the `decorationDebounceDelayMs` configuration
+ * value to determine the debounce delay.
+ */
+export class Debouncer {
+  private timeoutHandle: NodeJS.Timeout | null = null;
+
+  constructor(
+    /** The callback to debounce */
+    private callback: () => void,
+  ) {
+    this.run = this.run.bind(this);
+  }
+
+  run() {
+    if (this.timeoutHandle != null) {
+      clearTimeout(this.timeoutHandle);
+    }
+
+    const decorationDebounceDelayMs = ide().configuration.getOwnConfiguration(
+      "decorationDebounceDelayMs",
+    );
+
+    this.timeoutHandle = setTimeout(() => {
+      this.callback();
+      this.timeoutHandle = null;
+    }, decorationDebounceDelayMs);
+  }
+
+  dispose() {
+    if (this.timeoutHandle != null) {
+      clearTimeout(this.timeoutHandle);
+    }
+  }
+}

packages/cursorless-engine/src/core/HatAllocator.ts

@@ -2,44 +2,45 @@ import type { Disposable, Hats, TokenHat } from "@cursorless/common";
 import { ide } from "../singletons/ide.singleton";
 import tokenGraphemeSplitter from "../singletons/tokenGraphemeSplitter.singleton";
 import { allocateHats } from "../util/allocateHats";
+import { Debouncer } from "./Debouncer";
 import { IndividualHatMap } from "./IndividualHatMap";
 
 interface Context {
   getActiveMap(): Promise<IndividualHatMap>;
 }
 
 export class HatAllocator {
-  private timeoutHandle: NodeJS.Timeout | null = null;
   private disposables: Disposable[] = [];
+  private debouncer = new Debouncer(() => this.allocateHats());
 
   constructor(private hats: Hats, private context: Context) {
     ide().disposeOnExit(this);
 
-    this.allocateHatsDebounced = this.allocateHatsDebounced.bind(this);
-
     this.disposables.push(
-      this.hats.onDidChangeEnabledHatStyles(this.allocateHatsDebounced),
-      this.hats.onDidChangeIsEnabled(this.allocateHatsDebounced),
+      this.hats.onDidChangeEnabledHatStyles(this.debouncer.run),
+      this.hats.onDidChangeIsEnabled(this.debouncer.run),
 
       // An event that fires when a text document opens
-      ide().onDidOpenTextDocument(this.allocateHatsDebounced),
+      ide().onDidOpenTextDocument(this.debouncer.run),
       // An event that fires when a text document closes
-      ide().onDidCloseTextDocument(this.allocateHatsDebounced),
+      ide().onDidCloseTextDocument(this.debouncer.run),
       // An Event which fires when the active editor has changed. Note that the event also fires when the active editor changes to undefined.
-      ide().onDidChangeActiveTextEditor(this.allocateHatsDebounced),
+      ide().onDidChangeActiveTextEditor(this.debouncer.run),
       // An Event which fires when the array of visible editors has changed.
-      ide().onDidChangeVisibleTextEditors(this.allocateHatsDebounced),
+      ide().onDidChangeVisibleTextEditors(this.debouncer.run),
       // An event that is emitted when a text document is changed. This usually happens when the contents changes but also when other things like the dirty-state changes.
-      ide().onDidChangeTextDocument(this.allocateHatsDebounced),
+      ide().onDidChangeTextDocument(this.debouncer.run),
       // An Event which fires when the selection in an editor has changed.
-      ide().onDidChangeTextEditorSelection(this.allocateHatsDebounced),
+      ide().onDidChangeTextEditorSelection(this.debouncer.run),
       // An Event which fires when the visible ranges of an editor has changed.
-      ide().onDidChangeTextEditorVisibleRanges(this.allocateHatsDebounced),
+      ide().onDidChangeTextEditorVisibleRanges(this.debouncer.run),
       // Re-draw hats on grapheme splitting algorithm change in case they
       // changed their token hat splitting setting.
       tokenGraphemeSplitter().registerAlgorithmChangeListener(
-        this.allocateHatsDebounced,
+        this.debouncer.run,
       ),
+
+      this.debouncer,
     );
   }
 
@@ -75,26 +76,7 @@ export class HatAllocator {
     );
   }
 
-  allocateHatsDebounced() {
-    if (this.timeoutHandle != null) {
-      clearTimeout(this.timeoutHandle);
-    }
-
-    const decorationDebounceDelayMs = ide().configuration.getOwnConfiguration(
-      "decorationDebounceDelayMs",
-    );
-
-    this.timeoutHandle = setTimeout(() => {
-      this.allocateHats();
-      this.timeoutHandle = null;
-    }, decorationDebounceDelayMs);
-  }
-
   dispose() {
     this.disposables.forEach(({ dispose }) => dispose());
-
-    if (this.timeoutHandle != null) {
-      clearTimeout(this.timeoutHandle);
-    }
   }
 }