fix(linux): ensure icon works in sandboxed environments (#43)

* refactor: only pass icon as base64 for macOS

Only macOS requires the icon to be passed as a base64 string. No need
to do this for other platforms.

* fix(linux): ensure icon works in sandboxed environments

When running in a sandboxed environment, such as a Flatpak or Snap, the
icon should be passed as the icon name, not a path.

This is required because when running in a sandbox, paths are not the
same as seen by the app and the host system.

Author: Merrit

lib/src/helpers/sandbox.dart

@@ -0,0 +1,7 @@
+import 'dart:io';
+
+/// Returns `true` if the app is running in a sandbox, eg. Flatpak or Snap.
+bool runningInSandbox() {
+  return Platform.environment.containsKey('FLATPAK_ID') ||
+      Platform.environment.containsKey('SNAP');
+}

lib/src/tray_manager.dart

@@ -9,6 +9,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:shortid/shortid.dart';
 
+import 'helpers/sandbox.dart';
 import 'tray_listener.dart';
 
 const kEventOnTrayIconMouseDown = 'onTrayIconMouseDown';
@@ -90,25 +91,50 @@ class TrayManager {
   }
 
   /// Sets the image associated with this tray icon.
+  ///
+  /// [iconPath] is the path to the image file.
+  ///
+  /// However, if the app is running in a sandbox like Flatpak or Snap,
+  /// [iconPath] should be the name of the icon as specified in the app's
+  /// manifest file, without the path or file extension. For example, if the
+  /// icon is specified as `org.example.app` in the Flatpak manifest file, then
+  /// the icon should be passed as `org.example.app`.
   Future<void> setIcon(
     String iconPath, {
     bool isTemplate = false, // macOS only
     TrayIconPositon iconPosition = TrayIconPositon.left, // macOS only
   }) async {
-    ByteData imageData = await rootBundle.load(iconPath);
-    String base64Icon = base64Encode(imageData.buffer.asUint8List());
-
     final Map<String, dynamic> arguments = {
       "id": shortid.generate(),
       'iconPath': path.joinAll([
         path.dirname(Platform.resolvedExecutable),
         'data/flutter_assets',
         iconPath,
       ]),
-      'base64Icon': base64Icon,
       'isTemplate': isTemplate,
       'iconPosition': iconPosition.name,
     };
+
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.linux:
+        if (runningInSandbox()) {
+          // Pass the icon name as specified if running in a sandbox.
+          //
+          // This is required because when running in a sandbox, paths are not
+          // the same as seen by the app and the host system.
+          arguments['iconPath'] = iconPath;
+        }
+        break;
+      case TargetPlatform.macOS:
+        // Add the icon as base64 string
+        ByteData imageData = await rootBundle.load(iconPath);
+        String base64Icon = base64Encode(imageData.buffer.asUint8List());
+        arguments['base64Icon'] = base64Icon;
+        break;
+      default:
+        break;
+    }
+
     await _channel.invokeMethod('setIcon', arguments);
   }