[glfw] Send the glfw key data to the framework. (flutter#9386)

shell/platform/glfw/key_event_handler.cc

@@ -12,14 +12,95 @@ static constexpr char kChannelName[] = "flutter/keyevent";
 
 static constexpr char kKeyCodeKey[] = "keyCode";
 static constexpr char kKeyMapKey[] = "keymap";
+static constexpr char kScanCodeKey[] = "scanCode";
+static constexpr char kModifiersKey[] = "modifiers";
 static constexpr char kTypeKey[] = "type";
+static constexpr char kToolkitKey[] = "toolkit";
+static constexpr char kUnicodeScalarValues[] = "unicodeScalarValues";
+
+static constexpr char kLinuxKeyMap[] = "linux";
+static constexpr char kGLFWKey[] = "glfw";
 
-static constexpr char kAndroidKeyMap[] = "android";
 static constexpr char kKeyUp[] = "keyup";
 static constexpr char kKeyDown[] = "keydown";
 
+// Masks used for UTF-8 to UTF-32 conversion.
+static constexpr int kTwoByteMask = 0xC0;
+static constexpr int kThreeByteMask = 0xE0;
+static constexpr int kFourByteMask = 0xF0;
+
 namespace flutter {
 
+namespace {
+
+// Information about the UTF-8 encoded code point.
+struct UTF8CodePointInfo {
+  // The bit-mask that determines the length of the code point.
+  int first_byte_mask;
+  // The number of bytes of the code point.
+  size_t length;
+};
+
+// Creates a [UTF8CodePointInfo] from a given byte. [first_byte] must be the
+// first byte in the code point.
+UTF8CodePointInfo GetUTF8CodePointInfo(int first_byte) {
+  UTF8CodePointInfo byte_info;
+
+  // The order matters. Otherwise, it is possible that comparing against i.e.
+  // kThreeByteMask and kFourByteMask could be both true.
+  if ((first_byte & kFourByteMask) == kFourByteMask) {
+    byte_info.first_byte_mask = 0x07;
+    byte_info.length = 4;
+  } else if ((first_byte & kThreeByteMask) == kThreeByteMask) {
+    byte_info.first_byte_mask = 0x0F;
+    byte_info.length = 3;
+  } else if ((first_byte & kTwoByteMask) == kTwoByteMask) {
+    byte_info.first_byte_mask = 0x1F;
+    byte_info.length = 2;
+  } else {
+    byte_info.first_byte_mask = 0xFF;
+    byte_info.length = 1;
+  }
+  return byte_info;
+}
+
+// Queries GLFW for the printable key name given a [key] and [scan_code] and
+// converts it to UTF-32. The Flutter framework accepts only one code point,
+// therefore, only the first code point will be used. There is unlikely to be
+// more than one, but there is no guarantee that it won't happen.
+bool GetUTF32CodePointFromGLFWKey(int key,
+                                  int scan_code,
+                                  uint32_t* code_point) {
+  // Get the name of the printable key, encoded as UTF-8.
+  // There's a known issue with glfwGetKeyName, where users with multiple
+  // layouts configured on their machines, will not always return the right
+  // value. See: https://github.com/glfw/glfw/issues/1462
+  const char* utf8 = glfwGetKeyName(key, scan_code);
+  if (utf8 == nullptr) {
+    return false;
+  }
+  // The first byte determines the length of the whole code point.
+  const auto byte_info = GetUTF8CodePointInfo(utf8[0]);
+  // Tracks how many bits the current byte should shift to the left.
+  int shift = byte_info.length - 1;
+
+  const int complement_mask = 0x3F;
+  uint32_t result = 0;
+
+  size_t current_byte_index = 0;
+  while (current_byte_index < byte_info.length) {
+    const int current_byte = utf8[current_byte_index];
+    const int mask =
+        current_byte_index == 0 ? byte_info.first_byte_mask : complement_mask;
+    current_byte_index++;
+    const int bits_to_shift = 6 * shift--;
+    result += (current_byte & mask) << bits_to_shift;
+  }
+  *code_point = result;
+  return true;
+}
+}  // namespace
+
 KeyEventHandler::KeyEventHandler(flutter::BinaryMessenger* messenger)
     : channel_(
           std::make_unique<flutter::BasicMessageChannel<rapidjson::Document>>(
@@ -41,10 +122,20 @@ void KeyEventHandler::KeyboardHook(GLFWwindow* window,
   rapidjson::Document event(rapidjson::kObjectType);
   auto& allocator = event.GetAllocator();
   event.AddMember(kKeyCodeKey, key, allocator);
-  event.AddMember(kKeyMapKey, kAndroidKeyMap, allocator);
+  event.AddMember(kKeyMapKey, kLinuxKeyMap, allocator);
+  event.AddMember(kScanCodeKey, scancode, allocator);
+  event.AddMember(kModifiersKey, mods, allocator);
+  event.AddMember(kToolkitKey, kGLFWKey, allocator);
+
+  uint32_t unicodeInt;
+  bool result = GetUTF32CodePointFromGLFWKey(key, scancode, &unicodeInt);
+  if (result) {
+    event.AddMember(kUnicodeScalarValues, unicodeInt, allocator);
+  }
 
   switch (action) {
     case GLFW_PRESS:
+    case GLFW_REPEAT:
       event.AddMember(kTypeKey, kKeyDown, allocator);
       break;
     case GLFW_RELEASE: