Officially support the system tray on Windows

app/SystemTraySettingCache.ts

@@ -0,0 +1,84 @@
+// Copyright 2017-2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as log from '../ts/logging/log';
+import {
+  parseSystemTraySetting,
+  SystemTraySetting,
+} from '../ts/types/SystemTraySetting';
+import { isSystemTraySupported } from '../ts/types/Settings';
+import type { MainSQL } from '../ts/sql/main';
+
+/**
+ * A small helper class to get and cache the `system-tray-setting` preference in the main
+ * process.
+ */
+export class SystemTraySettingCache {
+  private cachedValue: undefined | SystemTraySetting;
+
+  private getPromise: undefined | Promise<SystemTraySetting>;
+
+  constructor(
+    private readonly sql: Pick<MainSQL, 'sqlCall'>,
+    private readonly argv: Array<string>
+  ) {}
+
+  async get(): Promise<SystemTraySetting> {
+    if (this.cachedValue !== undefined) {
+      return this.cachedValue;
+    }
+
+    this.getPromise = this.getPromise || this.doFirstGet();
+    return this.getPromise;
+  }
+
+  set(value: SystemTraySetting): void {
+    this.cachedValue = value;
+  }
+
+  private async doFirstGet(): Promise<SystemTraySetting> {
+    let result: SystemTraySetting;
+
+    // These command line flags are not officially supported, but many users rely on them.
+    //   Be careful when removing them or making changes.
+    if (this.argv.some(arg => arg === '--start-in-tray')) {
+      result = SystemTraySetting.MinimizeToAndStartInSystemTray;
+      log.info(
+        `getSystemTraySetting saw --start-in-tray flag. Returning ${result}`
+      );
+    } else if (this.argv.some(arg => arg === '--use-tray-icon')) {
+      result = SystemTraySetting.MinimizeToSystemTray;
+      log.info(
+        `getSystemTraySetting saw --use-tray-icon flag. Returning ${result}`
+      );
+    } else if (isSystemTraySupported()) {
+      const { value } = (await this.sql.sqlCall('getItemById', [
+        'system-tray-setting',
+      ])) || { value: undefined };
+
+      if (value !== undefined) {
+        result = parseSystemTraySetting(value);
+        log.info(
+          `getSystemTraySetting returning value from database, ${result}`
+        );
+      } else {
+        result = SystemTraySetting.DoNotUseSystemTray;
+        log.info(
+          `getSystemTraySetting got no value from database, returning ${result}`
+        );
+      }
+    } else {
+      result = SystemTraySetting.DoNotUseSystemTray;
+      log.info(
+        `getSystemTraySetting had no flags and did no DB lookups. Returning ${result}`
+      );
+    }
+
+    // If there's a value in the cache, someone has updated the value "out from under us",
+    //   so we should return that because it's newer.
+    this.cachedValue =
+      this.cachedValue === undefined ? result : this.cachedValue;
+
+    return this.cachedValue;
+  }
+}