Tony/88 load on linux

example/lib/main.dart

@@ -31,8 +31,8 @@
 library;
 
 import 'dart:async';
-import 'dart:io';
 
+import 'package:flutter/foundation.dart' show kIsWeb;
 import 'package:flutter/material.dart';
 
 import 'package:markdown_widget_builder/markdown_widget_builder.dart';
@@ -65,7 +65,7 @@ class _MarkdownExamplePageState extends State<MarkdownExamplePage> {
   bool _isLoadingConfig = true;
   Object? _configLoadError;
 
-  StreamSubscription<FileSystemEvent>? _fileWatchSub;
+  StreamSubscription<dynamic>? _fileWatchSub;
   String _markdownContent = 'Loading...';
 
   @override
@@ -103,11 +103,11 @@ class _MarkdownExamplePageState extends State<MarkdownExamplePage> {
       );
       setState(() => _markdownContent = content);
 
-      // Watch file changes (if local path is valid).
+      // Watch file changes (if local path is valid and not on web).
+      // watchFileChanges returns null on web or if file watching is unavailable.
 
-      final interpretedPath = await interpretPath(config.markdown.path);
-      final file = File(interpretedPath);
-      if (await file.exists()) {
+      if (!kIsWeb) {
+        final interpretedPath = await interpretPath(config.markdown.path);
         _fileWatchSub?.cancel();
         _fileWatchSub = watchFileChanges(
           interpretedPath,

lib/src/utils/file_ops.dart

@@ -32,18 +32,19 @@ library;
 
 import 'dart:async';
 import 'dart:convert';
-import 'dart:io';
 
+import 'package:flutter/foundation.dart' show kIsWeb;
 import 'package:flutter/services.dart' show rootBundle;
 
 import 'package:path/path.dart' as p;
-import 'package:path_provider/path_provider.dart'
-    show getApplicationDocumentsDirectory;
 
 import 'package:markdown_widget_builder/markdown_widget_builder.dart'
     show setMarkdownMediaPath;
 import 'package:markdown_widget_builder/src/constants/pkg.dart'
     show defaultConfigFile, mdPath, mediaPath;
+import 'package:markdown_widget_builder/src/utils/platform_io.dart'
+    if (dart.library.html) 'package:markdown_widget_builder/src/utils/platform_web.dart'
+    as platform_utils;
 
 /// Structure of md_config.json.
 
@@ -103,8 +104,14 @@ class Config {
 /// platforms.
 
 Future<String> getAppDirectory() async {
-  final os = Platform.operatingSystem;
-  final exePath = Platform.resolvedExecutable;
+  if (kIsWeb) {
+    // On web, return a fallback path as there is no file system access.
+
+    return '';
+  }
+
+  final os = platform_utils.getOperatingSystem();
+  final exePath = platform_utils.getResolvedExecutable();
 
   if (os == 'macos') {
     final exeDir = p.dirname(exePath);
@@ -115,8 +122,8 @@ Future<String> getAppDirectory() async {
   } else if (os == 'windows' || os == 'linux') {
     return p.dirname(exePath);
   } else if (os == 'android' || os == 'ios') {
-    final docDir = await getApplicationDocumentsDirectory();
-    return docDir.path;
+    final docDirPath = await platform_utils.getApplicationDocumentsPath();
+    return docDirPath;
   } else {
     return p.dirname(exePath);
   }
@@ -172,6 +179,13 @@ Future<void> loadMediaFiles(
   String rawMediaPath, {
   Function(String)? onError,
 }) async {
+  if (kIsWeb) {
+    // On web, always use asset path as there is no local file system access.
+
+    setMarkdownMediaPath(mediaPath);
+    return;
+  }
+
   if (rawMediaPath.trim().isEmpty) {
     // If the path is empty, fallback to assets.
 
@@ -184,9 +198,9 @@ Future<void> loadMediaFiles(
   }
 
   final interpretedMediaPath = await interpretPath(rawMediaPath);
-  Directory dir = Directory(interpretedMediaPath);
+  final dirExists = await platform_utils.directoryExists(interpretedMediaPath);
 
-  if (!await dir.exists()) {
+  if (!dirExists) {
     // If the media directory does not exist, fallback to the default.
 
     onError?.call('Media directory not found: $interpretedMediaPath. '
@@ -205,6 +219,24 @@ Future<String> loadMarkdownContent(
   String rawPath, {
   Function(String)? onError,
 }) async {
+  if (kIsWeb) {
+    // On web, always load from assets.
+
+    if (rawPath.trim().isEmpty) {
+      return rootBundle.loadString(mdPath);
+    }
+    try {
+      return await rootBundle.loadString(rawPath);
+    } catch (e) {
+      try {
+        return await rootBundle.loadString(mdPath);
+      } catch (e) {
+        onError?.call('Error loading asset: $e');
+        return 'Error: Could not load asset.';
+      }
+    }
+  }
+
   if (rawPath.trim().isEmpty) {
     // If the path is empty, fallback to assets.
 
@@ -214,9 +246,9 @@ Future<String> loadMarkdownContent(
     return rootBundle.loadString(mdPath);
   }
   final interpretedPath = await interpretPath(rawPath);
-  File file = File(interpretedPath);
+  final fileExists = await platform_utils.fileExists(interpretedPath);
 
-  if (!await file.exists()) {
+  if (!fileExists) {
     // If the file does not exist, fallback to assets.
 
     onError?.call('Markdown file not found at $interpretedPath. '
@@ -228,23 +260,40 @@ Future<String> loadMarkdownContent(
       return 'Error: Could not load fallback asset.';
     }
   } else {
-    return file.readAsString();
+    return platform_utils.readFileAsString(interpretedPath);
   }
 }
 
 /// File watcher. Returns a subscription object that the caller can cancel at
 /// an appropriate time.
+/// Returns null on web platform as file watching is not supported.
 
-StreamSubscription<FileSystemEvent> watchFileChanges(
+StreamSubscription<dynamic>? watchFileChanges(
   String filePath, {
   required void Function(String newContent) onFileContentChanged,
 }) {
-  final parentDir = Directory(p.dirname(filePath));
-  return parentDir.watch().listen((event) async {
-    if (event.type == FileSystemEvent.modify && event.path == filePath) {
-      final f = File(filePath);
-      if (await f.exists()) {
-        final updated = await f.readAsString();
+  if (kIsWeb) {
+    // File watching is not supported on web.
+
+    return null;
+  }
+
+  final parentDirPath = p.dirname(filePath);
+  final watchStream = platform_utils.watchDirectory(parentDirPath);
+
+  if (watchStream == null) {
+    return null;
+  }
+
+  return watchStream.listen((event) async {
+    // On non-web platforms, event is FileSystemEvent.
+
+    if (event.type == 2 && event.path == filePath) {
+      // type 2 is FileSystemEvent.modify
+
+      final fileExists = await platform_utils.fileExists(filePath);
+      if (fileExists) {
+        final updated = await platform_utils.readFileAsString(filePath);
         onFileContentChanged(updated);
       }
     }

lib/src/utils/platform_io.dart

@@ -0,0 +1,107 @@
+/// Platform utilities for non-web platforms (using dart:io).
+///
+/// Copyright (C) 2026, Software Innovation Institute, ANU.
+///
+/// Licensed under the MIT License (the "License").
+///
+/// License: https://choosealicense.com/licenses/mit/.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+///
+/// Authors: Tony Chen
+
+library;
+
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:path_provider/path_provider.dart'
+    show getTemporaryDirectory, getApplicationDocumentsDirectory;
+
+/// Checks if a file exists at the given path.
+/// Returns false on web platform.
+
+Future<bool> fileExists(String path) async {
+  final file = File(path);
+  return file.exists();
+}
+
+/// Writes bytes to a temporary file and returns the path.
+/// Throws on web platform.
+
+Future<String> writeBytesToTempFile(String filename, Uint8List bytes) async {
+  final tempDir = await getTemporaryDirectory();
+  final fileNameOnly = filename.split('/').last;
+  final tempPath = '${tempDir.path}/$fileNameOnly';
+  final tempFile = File(tempPath);
+  await tempFile.writeAsBytes(bytes);
+  return tempFile.path;
+}
+
+/// Returns the operating system name.
+/// Returns 'web' on web platform.
+
+String getOperatingSystem() {
+  return Platform.operatingSystem;
+}
+
+/// Returns the resolved executable path.
+/// Returns empty string on web platform.
+
+String getResolvedExecutable() {
+  return Platform.resolvedExecutable;
+}
+
+/// Returns the application documents directory path.
+/// Throws on web platform.
+
+Future<String> getApplicationDocumentsPath() async {
+  final docDir = await getApplicationDocumentsDirectory();
+  return docDir.path;
+}
+
+/// Checks if a directory exists at the given path.
+/// Returns false on web platform.
+
+Future<bool> directoryExists(String path) async {
+  final dir = Directory(path);
+  return dir.exists();
+}
+
+/// Reads a file as a string.
+/// Throws on web platform.
+
+Future<String> readFileAsString(String path) async {
+  final file = File(path);
+  return file.readAsString();
+}
+
+/// Creates a Directory object for watching file changes.
+/// Returns null on web platform.
+
+Stream<FileSystemEvent>? watchDirectory(String path) {
+  return Directory(path).watch();
+}
+
+/// Creates a File object from a path.
+/// Throws on web platform.
+
+File createFile(String path) {
+  return File(path);
+}