Fix unread count taskbar badge for Windows

_locales/en/messages.json

@@ -591,6 +591,14 @@
     "messageformat": "{count, plural, one {# Unread Message} other {# Unread Messages}}",
     "description": "Text for unread message separator, with count"
   },
+  "icu:taskbarMarkedUnread": {
+    "messageformat": "Marked Unread",
+    "description": "On Windows, description for screen readers for the OS taskbar icon's overlay badge when the user has marked chat(s) as unread."
+  },
+  "icu:taskbarUnreadMessages": {
+    "messageformat": "{count, plural, one {# Unread Message} other {# Unread Messages}}",
+    "description": "On Windows, description for screen readers for the OS taskbar icon's overlay badge when there are unread messages."
+  },
   "icu:messageHistoryUnsynced": {
     "messageformat": "For your security, chat history isn't transferred to new linked devices.",
     "description": "Shown in the conversation history when a user links a new device to explain what is not supported."

app/main.ts

@@ -114,6 +114,7 @@ import type { ParsedSignalRoute } from '../ts/util/signalRoutes';
 import { parseSignalRoute } from '../ts/util/signalRoutes';
 import * as dns from '../ts/util/dns';
 import { ZoomFactorService } from '../ts/services/ZoomFactorService';
+import { getMarkedUnreadIcon, getUnreadIcon } from '../ts/util/unreadIcon';
 
 const STICKER_CREATOR_PARTITION = 'sticker-creator';
 
@@ -2266,10 +2267,44 @@ ipc.on(
       if (process.platform === 'darwin') {
         // Will show a ● on macOS when undefined
         app.setBadgeCount(undefined);
+      } else if (process.platform === 'win32') {
+        // setBadgeCount is unsupported on Windows, so we use setOverlayIcon
+        let description;
+        try {
+          description = getResolvedMessagesLocale().i18n(
+            'icu:taskbarMarkedUnread'
+          );
+        } catch {
+          description = 'Unread';
+        }
+        mainWindow?.setOverlayIcon(getMarkedUnreadIcon(), description);
       } else {
         // All other OS's need a number
         app.setBadgeCount(1);
       }
+      return;
+    }
+
+    if (process.platform === 'win32') {
+      if (!mainWindow) {
+        return;
+      }
+
+      let description;
+      try {
+        description = getResolvedMessagesLocale().i18n(
+          'icu:taskbarUnreadMessages',
+          { count: badge }
+        );
+      } catch {
+        description = String(badge);
+      }
+
+      if (badge === 0) {
+        mainWindow.setOverlayIcon(null, '');
+      } else {
+        mainWindow.setOverlayIcon(getUnreadIcon(badge), description);
+      }
     } else {
       app.setBadgeCount(badge);
     }

ts/util/unreadIcon.ts

@@ -0,0 +1,26 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { join } from 'path';
+import type { NativeImage } from 'electron';
+import { nativeImage } from 'electron';
+
+export function getUnreadIcon(unreadCount: number): NativeImage {
+  const filename =
+    unreadCount > 9 ? '9-plus.png' : `${String(unreadCount)}.png`;
+  const path = join(__dirname, '..', '..', 'images', 'unread-icon', filename);
+  // if path does not exist, this returns an empty NativeImage
+  return nativeImage.createFromPath(path);
+}
+
+export function getMarkedUnreadIcon(): NativeImage {
+  const path = join(
+    __dirname,
+    '..',
+    '..',
+    'images',
+    'unread-icon',
+    'marked-unread.png'
+  );
+  return nativeImage.createFromPath(path);
+}