Add C++ code generation for key maps. (#50998)

This adds generation of some C++ keycode maps for various platforms.

This isn't meant for general use: it's so that the Flutter authors can keep the keycodes up to date with the Chromium and Android (and other) sources. It doesn't run continuously, it's only run occasionally (manually) to update the maps, because they don't change very often, and there is often manual work needed to make it function.

In this PR, I added output of various .cc files that write into an engine repo situated next to the flutter repo on disk. This is a starting point for implementing platform-side handling of key events.

dev/tools/gen_keycodes/bin/gen_keycodes.dart

@@ -7,10 +7,11 @@ import 'dart:convert';
 import 'dart:io' hide Platform;
 
 import 'package:args/args.dart';
+import 'package:gen_keycodes/cc_code_gen.dart';
 import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as path;
 
-import 'package:gen_keycodes/code_gen.dart';
+import 'package:gen_keycodes/dart_code_gen.dart';
 import 'package:gen_keycodes/key_data.dart';
 import 'package:gen_keycodes/utils.dart';
 
@@ -215,7 +216,24 @@ Future<void> main(List<String> rawArguments) async {
     mapsFile.createSync(recursive: true);
   }
 
-  final CodeGenerator generator = CodeGenerator(data);
+  final DartCodeGenerator generator = DartCodeGenerator(data);
   await codeFile.writeAsString(generator.generateKeyboardKeys());
   await mapsFile.writeAsString(generator.generateKeyboardMaps());
+
+  final CcCodeGenerator ccCodeGenerator = CcCodeGenerator(data);
+  for (final String platform in <String>['android', 'darwin', 'glfw', 'fuchsia', 'linux', 'windows']) {
+    final File platformFile = File(path.join(flutterRoot.path, '..', path.join('engine', 'src', 'flutter', 'shell', 'platform', platform, 'keycodes', 'keyboard_map_$platform.h')));
+    if (!platformFile.existsSync()) {
+      platformFile.createSync(recursive: true);
+    }
+    print('Writing map ${platformFile.absolute}');
+    await platformFile.writeAsString(ccCodeGenerator.generateKeyboardMaps(platform));
+  }
+
+  final File webPlatformFile = File(path.join(flutterRoot.path, '..', 'engine', 'src', 'flutter', path.join('lib', 'web_ui', 'lib', 'src', 'engine', 'keycodes', 'keyboard_map_web.dart')));
+  if (!webPlatformFile.existsSync()) {
+    webPlatformFile.createSync(recursive: true);
+  }
+  print('Writing map ${webPlatformFile.absolute}');
+  await webPlatformFile.writeAsString(generator.generateWebKeyboardMap());
 }

dev/tools/gen_keycodes/data/key_data.json

@@ -191,6 +191,29 @@
       "windows": null
     }
   },
+  "privacyScreenToggle": {
+    "names": {
+      "domkey": "PrivacyScreenToggle",
+      "android": null,
+      "english": "Privacy Screen Toggle",
+      "chromium": "privacyScreenToggle",
+      "glfw": null,
+      "windows": null
+    },
+    "scanCodes": {
+      "android": null,
+      "usb": 23,
+      "linux": 633,
+      "xkb": 641,
+      "windows": null,
+      "macos": null
+    },
+    "keyCodes": {
+      "android": null,
+      "glfw": null,
+      "windows": null
+    }
+  },
   "sleep": {
     "names": {
       "domkey": "Sleep",
@@ -8253,4 +8276,4 @@
       "windows": null
     }
   }
-}
+}
\ No newline at end of file

dev/tools/gen_keycodes/data/keyboard_map_android_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_android_cxx.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+// Maps Android-specific key codes to the matching LogicalKeyboardKey id.
+const std::map<int, int> g_android_to_logical_key = {
+@@@ANDROID_KEY_CODE_MAP@@@
+};
+
+// Maps Android-specific scan codes to the matching PhysicalKeyboardKey id (a.k.a. HID USB code).
+const std::map<int, int> g_android_to_physical_key = {
+@@@ANDROID_SCAN_CODE_MAP@@@
+};
+
+// A map of Android key codes which have printable representations, but appear
+// on the number pad. Used to provide different key objects for keys like
+// KEY_EQUALS and NUMPAD_EQUALS. Maps Android key codes to PhysicalKeyboardKey
+// codes (USB HID codes).
+const std::map<int, int> g_android_numpad_map = {
+@@@ANDROID_NUMPAD_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_darwin_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_android_cxx.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+// Maps macOS-specific key code values representing [PhysicalKeyboardKey].
+//
+// MacOS doesn't provide a scan code, but a virtual keycode to represent a physical key.
+const std::map<int, int> g_macos_to_physical_key = {
+@@@MACOS_SCAN_CODE_MAP@@@
+};
+
+// A map of macOS key codes which have printable representations, but appear
+// on the number pad. Used to provide different key objects for keys like
+// KEY_EQUALS and NUMPAD_EQUALS.
+const std::map<int, int> g_macos_numpad_map = {
+@@@MACOS_NUMPAD_MAP@@@
+};
+
+// A map of macOS key codes which are numbered function keys, so that they
+// can be excluded when asking "is the Fn modifier down?".
+const std::map<int, int> g_macos_function_key_map = {
+@@@MACOS_FUNCTION_KEY_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_fuchsia_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_android_cxx.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+/// Maps Fuchsia-specific IDs to the matching LogicalKeyboardKey.
+const std::map<int, int> g_fuchsia_to_logical_key = {
+@@@FUCHSIA_KEY_CODE_MAP@@@
+};
+
+/// Maps Fuchsia-specific USB HID Usage IDs to the matching
+/// [PhysicalKeyboardKey].
+const std::map<int, int> g_fuchsia_to_physical_key = {
+@@@FUCHSIA_SCAN_CODE_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_glfw_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_android_cxx.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+/// Maps GLFW-specific key codes to the matching [LogicalKeyboardKey].
+const std::map<int, int> g_glfw_to_logical_key = {
+@@@GLFW_KEY_CODE_MAP@@@
+};
+
+/// A map of GLFW key codes which have printable representations, but appear
+/// on the number pad. Used to provide different key objects for keys like
+/// KEY_EQUALS and NUMPAD_EQUALS.
+const std::map<int, int> g_glfw_numpad_map = {
+@@@GLFW_NUMPAD_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_linux_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_android_cxx.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+/// Maps XKB specific key code values representing [PhysicalKeyboardKey].
+const std::map<int, int> g_xkb_to_physical_key = {
+@@@XKB_SCAN_CODE_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_web.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+/// Maps Web KeyboardEvent codes to the matching LogicalKeyboardKey id.
+const Map<String, int> kWebToLogicalKey = <String, int>{
+@@@WEB_LOGICAL_KEY_CODE_MAP@@@
+};
+
+/// Maps Web KeyboardEvent codes to the matching PhysicalKeyboardKey USB HID code.
+const Map<String, int> kWebToPhysicalKey = <String, int>{
+@@@WEB_PHYSICAL_KEY_CODE_MAP@@@
+};
+
+/// A map of Web KeyboardEvent codes which have printable representations, but appear
+/// on the number pad. Used to provide different key objects for keys like
+/// KEY_EQUALS and NUMPAD_EQUALS.
+const Map<String, int> kWebNumPadMap = <String, int>{
+@@@WEB_NUMPAD_CODE_MAP@@@
+};

dev/tools/gen_keycodes/data/keyboard_map_windows_cc.tmpl

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/keyboard_maps_windows_cc.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+/// Maps g_windows_to_physical_key specific key code values representing [PhysicalKeyboardKey].
+const std::map<int, uint64_t> g_windows_to_physical_key = {
+@@@WINDOWS_SCAN_CODE_MAP@@@
+};
+
+/// Maps Windows-specific key codes to the matching [LogicalKeyboardKey].
+const std::map<int, uint64_t> g_windows_to_logical_key = {
+@@@WINDOWS_KEY_CODE_MAP@@@
+};
+
+/// A map of GLFW key codes which have printable representations, but appear
+/// on the number pad. Used to provide different key objects for keys like
+/// KEY_EQUALS and NUMPAD_EQUALS.
+const std::map<int, uint64_t> g_windows_numpad_map = {
+@@@WINDOWS_NUMPAD_MAP@@@
+};

dev/tools/gen_keycodes/lib/cc_code_gen.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+import 'package:path/path.dart' as path;
+
+import 'package:gen_keycodes/key_data.dart';
+import 'package:gen_keycodes/utils.dart';
+
+/// Generates the keyboard_keys.dart and keyboard_maps.dart files, based on the
+/// information in the key data structure given to it.
+class CcCodeGenerator {
+  CcCodeGenerator(this.keyData);
+
+  /// Given an [input] string, wraps the text at 80 characters and prepends each
+  /// line with the [prefix] string. Use for generated comments.
+  String wrapString(String input, {String prefix = '  // '}) {
+    final int wrapWidth = 80 - prefix.length;
+    final StringBuffer result = StringBuffer();
+    final List<String> words = input.split(RegExp(r'\s+'));
+    String currentLine = words.removeAt(0);
+    for (final String word in words) {
+      if ((currentLine.length + word.length) < wrapWidth) {
+        currentLine += ' $word';
+      } else {
+        result.writeln('$prefix$currentLine');
+        currentLine = word;
+      }
+    }
+    if (currentLine.isNotEmpty) {
+      result.writeln('$prefix$currentLine');
+    }
+    return result.toString();
+  }
+
+  List<Key> get numpadKeyData {
+    return keyData.data.where((Key entry) {
+      return entry.constantName.startsWith('numpad') && entry.keyLabel != null;
+    }).toList();
+  }
+
+  List<Key> get functionKeyData {
+    final RegExp functionKeyRe = RegExp(r'^f[0-9]+$');
+    return keyData.data.where((Key entry) {
+      return functionKeyRe.hasMatch(entry.constantName);
+    }).toList();
+  }
+
+  /// This generates the map of Flutter key codes to logical keys.
+  String get predefinedKeyCodeMap {
+    final StringBuffer keyCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      keyCodeMap.writeln('    ${toHex(entry.flutterId, digits: 10)}: ${entry.constantName},');
+    }
+    for (final String entry in Key.synonyms.keys) {
+      // Use the first item in the synonyms as a template for the ID to use.
+      // It won't end up being the same value because it'll be in the pseudo-key
+      // plane.
+      final Key primaryKey = keyData.data.firstWhere((Key item) {
+        return item.name == Key.synonyms[entry][0];
+      }, orElse: () => null);
+      assert(primaryKey != null);
+      keyCodeMap.writeln('    ${toHex(Key.synonymPlane | primaryKey.flutterId, digits: 10)}: $entry,');
+    }
+    return keyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of GLFW number pad key codes to logical keys.
+  String get glfwNumpadMap {
+    final StringBuffer glfwNumpadMap = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.glfwKeyCodes != null) {
+        for (final int code in entry.glfwKeyCodes.cast<int>()) {
+          glfwNumpadMap.writeln('  { $code, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return glfwNumpadMap.toString().trimRight();
+  }
+
+  /// This generates the map of GLFW key codes to logical keys.
+  String get glfwKeyCodeMap {
+    final StringBuffer glfwKeyCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.glfwKeyCodes != null) {
+        for (final int code in entry.glfwKeyCodes.cast<int>()) {
+          glfwKeyCodeMap.writeln('  { $code, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return glfwKeyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of XKB scan codes to USB HID codes.
+  String get xkbScanCodeMap {
+    final StringBuffer xkbScanCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.xKbScanCode != null) {
+        xkbScanCodeMap.writeln('  { ${toHex(entry.xKbScanCode)}, ${toHex(entry.usbHidCode)} },    // ${entry.constantName}');
+      }
+    }
+    return xkbScanCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Android key codes to logical keys.
+  String get androidKeyCodeMap {
+    final StringBuffer androidKeyCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.androidKeyCodes != null) {
+        for (final int code in entry.androidKeyCodes.cast<int>()) {
+          androidKeyCodeMap.writeln('  { $code, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return androidKeyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Android number pad key codes to logical keys.
+  String get androidNumpadMap {
+    final StringBuffer androidKeyCodeMap = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.androidKeyCodes != null) {
+        for (final int code in entry.androidKeyCodes.cast<int>()) {
+          androidKeyCodeMap.writeln('  { $code, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return androidKeyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Android scan codes to physical keys.
+  String get androidScanCodeMap {
+    final StringBuffer androidScanCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.androidScanCodes != null) {
+        for (final int code in entry.androidScanCodes.cast<int>()) {
+          androidScanCodeMap.writeln('  { $code, ${toHex(entry.usbHidCode)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return androidScanCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Windows scan codes to physical keys.
+  String get windowsScanCodeMap {
+    final StringBuffer windowsScanCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.windowsScanCode != null) {
+        windowsScanCodeMap.writeln('  { ${entry.windowsScanCode}, ${toHex(entry.usbHidCode)} },    // ${entry.constantName}');
+      }
+    }
+    return windowsScanCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Windows number pad key codes to logical keys.
+  String get windowsNumpadMap {
+    final StringBuffer windowsNumPadMap = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.windowsScanCode != null) {
+        windowsNumPadMap.writeln('  { ${toHex(entry.windowsScanCode)}, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+      }
+    }
+    return windowsNumPadMap.toString().trimRight();
+  }
+
+  /// This generates the map of Android key codes to logical keys.
+  String get windowsKeyCodeMap {
+    final StringBuffer windowsKeyCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.windowsKeyCodes != null) {
+        for (final int code in entry.windowsKeyCodes.cast<int>()) {
+          windowsKeyCodeMap.writeln('  { $code, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+        }
+      }
+    }
+    return windowsKeyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of macOS key codes to physical keys.
+  String get macOsScanCodeMap {
+    final StringBuffer macOsScanCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.macOsScanCode != null) {
+        macOsScanCodeMap.writeln('  { ${toHex(entry.macOsScanCode)}, ${toHex(entry.usbHidCode)} },    // ${entry.constantName}');
+      }
+    }
+    return macOsScanCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of macOS number pad key codes to logical keys.
+  String get macOsNumpadMap {
+    final StringBuffer macOsNumPadMap = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.macOsScanCode != null) {
+        macOsNumPadMap.writeln('  { ${toHex(entry.macOsScanCode)}, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+      }
+    }
+    return macOsNumPadMap.toString().trimRight();
+  }
+
+  String get macOsFunctionKeyMap {
+    final StringBuffer macOsFunctionKeyMap = StringBuffer();
+    for (final Key entry in functionKeyData) {
+      if (entry.macOsScanCode != null) {
+        macOsFunctionKeyMap.writeln('  { ${toHex(entry.macOsScanCode)}, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+      }
+    }
+    return macOsFunctionKeyMap.toString().trimRight();
+  }
+
+  /// This generates the map of Fuchsia key codes to logical keys.
+  String get fuchsiaKeyCodeMap {
+    final StringBuffer fuchsiaKeyCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.usbHidCode != null) {
+        fuchsiaKeyCodeMap.writeln('  { ${toHex(entry.flutterId)}, ${toHex(entry.flutterId, digits: 10)} },    // ${entry.constantName}');
+      }
+    }
+    return fuchsiaKeyCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Fuchsia USB HID codes to physical keys.
+  String get fuchsiaHidCodeMap {
+    final StringBuffer fuchsiaScanCodeMap = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.usbHidCode != null) {
+        fuchsiaScanCodeMap.writeln(' { ${toHex(entry.usbHidCode)}, ${toHex(entry.usbHidCode)} },    // ${entry.constantName}');
+      }
+    }
+    return fuchsiaScanCodeMap.toString().trimRight();
+  }
+
+  /// This generates the map of Web KeyboardEvent codes to logical keys.
+  String get webLogicalKeyMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.flutterId, digits: 10)},    // ${entry.constantName}");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
+  /// This generates the map of Web KeyboardEvent codes to physical keys.
+  String get webPhysicalKeyMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.usbHidCode)},    // ${entry.constantName}");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
+  /// This generates the map of Web number pad codes to logical keys.
+  String get webNumpadMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.flutterId, digits: 10)},    // ${entry.constantName}");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
+  /// Substitutes the various platform specific maps into the template file for
+  /// keyboard_maps.dart.
+  String generateKeyboardMaps(String platform) {
+    // There is no macOS keycode map since macOS uses keycode to represent a physical key.
+    // The LogicalKeyboardKey is generated by raw_keyboard_macos.dart from the unmodified characters
+    // from NSEvent.
+    final Map<String, String> mappings = <String, String>{
+      'ANDROID_SCAN_CODE_MAP': androidScanCodeMap,
+      'ANDROID_KEY_CODE_MAP': androidKeyCodeMap,
+      'ANDROID_NUMPAD_MAP': androidNumpadMap,
+      'FUCHSIA_SCAN_CODE_MAP': fuchsiaHidCodeMap,
+      'FUCHSIA_KEY_CODE_MAP': fuchsiaKeyCodeMap,
+      'MACOS_SCAN_CODE_MAP': macOsScanCodeMap,
+      'MACOS_NUMPAD_MAP': macOsNumpadMap,
+      'MACOS_FUNCTION_KEY_MAP': macOsFunctionKeyMap,
+      'GLFW_KEY_CODE_MAP': glfwKeyCodeMap,
+      'GLFW_NUMPAD_MAP': glfwNumpadMap,
+      'XKB_SCAN_CODE_MAP': xkbScanCodeMap,
+      'WEB_LOGICAL_KEY_MAP': webLogicalKeyMap,
+      'WEB_PHYSICAL_KEY_MAP': webPhysicalKeyMap,
+      'WEB_NUMPAD_MAP': webNumpadMap,
+      'WINDOWS_SCAN_CODE_MAP': windowsScanCodeMap,
+      'WINDOWS_NUMPAD_MAP': windowsNumpadMap,
+      'WINDOWS_KEY_CODE_MAP': windowsKeyCodeMap,
+    };
+
+    final String template = File(path.join(flutterRoot.path, 'dev', 'tools', 'gen_keycodes', 'data', 'keyboard_map_${platform}_cc.tmpl')).readAsStringSync();
+    return _injectDictionary(template, mappings);
+  }
+
+  /// The database of keys loaded from disk.
+  final KeyData keyData;
+
+  static String _injectDictionary(String template, Map<String, String> dictionary) {
+    String result = template;
+    for (final String key in dictionary.keys) {
+      result = result.replaceAll('@@@$key@@@', dictionary[key]);
+    }
+    return result;
+  }
+}

dev/tools/gen_keycodes/lib/code_gen.dart → dev/tools/gen_keycodes/lib/dart_code_gen.dart

@@ -10,8 +10,8 @@ import 'package:gen_keycodes/utils.dart';
 
 /// Generates the keyboard_keys.dart and keyboard_maps.dart files, based on the
 /// information in the key data structure given to it.
-class CodeGenerator {
-  CodeGenerator(this.keyData);
+class DartCodeGenerator {
+  DartCodeGenerator(this.keyData);
 
   /// Given an [input] string, wraps the text at 80 characters and prepends each
   /// line with the [prefix] string. Use for generated comments.
@@ -130,7 +130,7 @@ $otherComments  static const LogicalKeyboardKey $constantName = LogicalKeyboardK
     return scanCodeMap.toString().trimRight();
   }
 
-  /// THis generates the map of Flutter key codes to logical keys.
+  /// This generates the map of Flutter key codes to logical keys.
   String get predefinedKeyCodeMap {
     final StringBuffer keyCodeMap = StringBuffer();
     for (final Key entry in keyData.data) {
@@ -312,6 +312,39 @@ $otherComments  static const LogicalKeyboardKey $constantName = LogicalKeyboardK
     return result.toString().trimRight();
   }
 
+  /// This generates the map of Web KeyboardEvent codes to logical key ids.
+  String get webLogicalKeyCodeMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.flutterId, digits: 10)},");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
+  /// This generates the map of Web KeyboardEvent codes to physical key USB HID codes.
+  String get webPhysicalKeyCodeMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in keyData.data) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.usbHidCode)},");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
+  /// This generates the map of Web number pad codes to logical key ids.
+  String get webNumpadCodeMap {
+    final StringBuffer result = StringBuffer();
+    for (final Key entry in numpadKeyData) {
+      if (entry.name != null) {
+        result.writeln("  '${entry.name}': ${toHex(entry.flutterId, digits: 10)},");
+      }
+    }
+    return result.toString().trimRight();
+  }
+
   /// Substitutes the various maps and definitions into the template file for
   /// keyboard_key.dart.
   String generateKeyboardKeys() {
@@ -354,6 +387,19 @@ $otherComments  static const LogicalKeyboardKey $constantName = LogicalKeyboardK
     return _injectDictionary(template, mappings);
   }
 
+  /// Substitutes the web specific maps into the template file for
+  /// keyboard_map_web.dart in the engine.
+  String generateWebKeyboardMap() {
+    final Map<String, String> mappings = <String, String>{
+      'WEB_LOGICAL_KEY_CODE_MAP': webLogicalKeyCodeMap,
+      'WEB_PHYSICAL_KEY_CODE_MAP': webPhysicalKeyCodeMap,
+      'WEB_NUMPAD_CODE_MAP': webNumpadCodeMap,
+    };
+
+    final String template = File(path.join(flutterRoot.path, 'dev', 'tools', 'gen_keycodes', 'data', 'keyboard_map_web.tmpl')).readAsStringSync();
+    return _injectDictionary(template, mappings);
+  }
+
   /// The database of keys loaded from disk.
   final KeyData keyData;