Prevent display sleep while on a call

app/PreventDisplaySleepService.ts

@@ -0,0 +1,40 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { PowerSaveBlocker } from 'electron';
+import * as log from '../ts/logging/log';
+
+export class PreventDisplaySleepService {
+  private blockerId: undefined | number;
+
+  constructor(private powerSaveBlocker: PowerSaveBlocker) {}
+
+  setEnabled(isEnabled: boolean): void {
+    log.info(
+      `Prevent display sleep service: ${
+        isEnabled ? 'preventing' : 'allowing'
+      } display sleep`
+    );
+
+    if (isEnabled) {
+      this.enable();
+    } else {
+      this.disable();
+    }
+  }
+
+  private enable(): void {
+    if (this.blockerId !== undefined) {
+      return;
+    }
+    this.blockerId = this.powerSaveBlocker.start('prevent-display-sleep');
+  }
+
+  private disable(): void {
+    if (this.blockerId === undefined) {
+      return;
+    }
+    this.powerSaveBlocker.stop(this.blockerId);
+    delete this.blockerId;
+  }
+}