Fix dead key crashes on Win32

shell/platform/windows/keyboard_key_embedder_handler.cc

@@ -37,6 +37,16 @@ char _GetBit(char32_t ch, size_t start, size_t end) {
   return (ch >> end) & ((1 << (start - end)) - 1);
 }
 
+// Revert the "character" for a dead key to its normal value.
+//
+// When a dead key is pressed, the WM_KEYDOWN's lParam is mapped to a special
+// value: the "normal character" | 0x80000000.  For example, when pressing
+// "dead key caret" (one that makes the following e into ê), its mapped
+// character is 0x8000005E. "Reverting" it gives 0x5E, which is character '^'.
+uint32_t _UndeadChar(uint32_t ch) {
+  return ch & ~0x80000000;
+}
+
 std::string ConvertChar32ToUtf8(char32_t ch) {
   std::string result;
   assert(0 <= ch && ch <= 0x10FFFF);
@@ -171,6 +181,8 @@ void KeyboardKeyEmbedderHandler::KeyboardHook(
   bool next_has_record = true;
   char character_bytes[kCharacterCacheSize];
 
+  character = _UndeadChar(character);
+
   if (is_physical_down) {
     if (had_record) {
       if (was_down) {

shell/platform/windows/keyboard_unittests.cc

@@ -43,13 +43,30 @@ static LPARAM CreateKeyEventLparam(USHORT scancode,
           (LPARAM(scancode) << 16) | LPARAM(repeat_count));
 }
 
+typedef uint32_t (*MapVkToCharHandler)(uint32_t virtual_key);
+
+uint32_t LayoutDefault(uint32_t virtual_key) {
+  return MapVirtualKey(virtual_key, MAPVK_VK_TO_CHAR);
+}
+
+uint32_t LayoutFrench(uint32_t virtual_key) {
+  switch (virtual_key) {
+    case 0xDD:
+      return 0x8000005E;
+    default:
+      return MapVirtualKey(virtual_key, MAPVK_VK_TO_CHAR);
+  }
+}
+
 class MockFlutterWindowWin32 : public FlutterWindowWin32,
                                public MockMessageQueue {
  public:
   typedef std::function<void(const std::u16string& text)> U16StringHandler;
 
   MockFlutterWindowWin32(U16StringHandler on_text)
-      : FlutterWindowWin32(800, 600), on_text_(std::move(on_text)) {
+      : FlutterWindowWin32(800, 600),
+        on_text_(std::move(on_text)),
+        map_vk_to_char_(LayoutDefault) {
     ON_CALL(*this, GetDpiScale())
         .WillByDefault(Return(this->FlutterWindowWin32::GetDpiScale()));
   }
@@ -90,6 +107,12 @@ class MockFlutterWindowWin32 : public FlutterWindowWin32,
   MOCK_METHOD0(IsVisible, bool());
   MOCK_METHOD1(UpdateCursorRect, void(const Rect&));
 
+  void SetLayout(MapVkToCharHandler map_vk_to_char) {
+    map_vk_to_char_ =
+        map_vk_to_char == nullptr ? LayoutDefault : map_vk_to_char;
+  }
+
+ protected:
   virtual BOOL Win32PeekMessage(LPMSG lpMsg,
                                 HWND hWnd,
                                 UINT wMsgFilterMin,
@@ -99,9 +122,15 @@ class MockFlutterWindowWin32 : public FlutterWindowWin32,
                                               wMsgFilterMax, wRemoveMsg);
   }
 
+  virtual uint32_t Win32MapVkToChar(uint32_t virtual_key) override {
+    return map_vk_to_char_(virtual_key);
+  }
+
  private:
   U16StringHandler on_text_;
 
+  MapVkToCharHandler map_vk_to_char_;
+
   LRESULT Win32SendMessage(HWND hWnd,
                            UINT const message,
                            WPARAM const wparam,
@@ -248,6 +277,8 @@ class KeyboardTester {
 
   void Responding(bool response) { test_response = response; }
 
+  void SetLayout(MapVkToCharHandler layout) { window_->SetLayout(layout); }
+
   void InjectMessages(int count, Win32Message message1, ...) {
     Win32Message messages[count];
     messages[0] = message1;
@@ -636,7 +667,7 @@ TEST(KeyboardTest, Digit1OnFrenchLayout) {
   KeyboardTester tester;
   tester.Responding(false);
 
-  // French Keyboard layout
+  tester.SetLayout(LayoutFrench);
 
   // Press 1
   tester.InjectMessages(
@@ -755,7 +786,7 @@ TEST(KeyboardTest, DeadKeyThatCombines) {
   KeyboardTester tester;
   tester.Responding(false);
 
-  // French Keyboard layout
+  tester.SetLayout(LayoutFrench);
 
   // Press ^¨ (US: Left bracket)
   tester.InjectMessages(
@@ -767,7 +798,7 @@ TEST(KeyboardTest, DeadKeyThatCombines) {
 
   EXPECT_EQ(key_calls.size(), 1);
   EXPECT_CALL_IS_EVENT(key_calls[0], kFlutterKeyEventTypeDown,
-                       kPhysicalBracketLeft, kLogicalBracketRight, "]",
+                       kPhysicalBracketLeft, kLogicalBracketRight, "^",
                        kNotSynthesized);
   clear_key_calls();
 
@@ -829,7 +860,7 @@ TEST(KeyboardTest, DeadKeyThatDoesNotCombine) {
   KeyboardTester tester;
   tester.Responding(false);
 
-  // French Keyboard layout
+  tester.SetLayout(LayoutFrench);
 
   // Press ^¨ (US: Left bracket)
   tester.InjectMessages(
@@ -841,7 +872,7 @@ TEST(KeyboardTest, DeadKeyThatDoesNotCombine) {
 
   EXPECT_EQ(key_calls.size(), 1);
   EXPECT_CALL_IS_EVENT(key_calls[0], kFlutterKeyEventTypeDown,
-                       kPhysicalBracketLeft, kLogicalBracketRight, "]",
+                       kPhysicalBracketLeft, kLogicalBracketRight, "^",
                        kNotSynthesized);
   clear_key_calls();
 

shell/platform/windows/window_win32.cc

@@ -373,7 +373,7 @@ WindowWin32::HandleMessage(UINT const message,
         // https://docs.microsoft.com/en-us/windows/win32/learnwin32/accelerator-tables
         const char32_t event_character =
             (message == WM_DEADCHAR || message == WM_SYSDEADCHAR)
-                ? MapVirtualKey(keycode_for_char_message_, MAPVK_VK_TO_CHAR)
+                ? Win32MapVkToChar(keycode_for_char_message_)
             : IsPrintable(code_point) ? code_point
                                       : 0;
         bool handled = OnKey(keycode_for_char_message_, scancode, WM_KEYDOWN,
@@ -429,7 +429,7 @@ WindowWin32::HandleMessage(UINT const message,
       // character messages. This allows key combinations such as "CTRL + Digit"
       // to properly produce key down events even though `MapVirtualKey` returns
       // a valid character. See https://github.com/flutter/flutter/issues/85587.
-      unsigned int character = MapVirtualKey(wparam, MAPVK_VK_TO_CHAR);
+      unsigned int character = Win32MapVkToChar(wparam);
       UINT next_key_message = PeekNextMessageType(WM_KEYFIRST, WM_KEYLAST);
       bool has_wm_char =
           (next_key_message == WM_DEADCHAR ||
@@ -516,4 +516,8 @@ BOOL WindowWin32::Win32PeekMessage(LPMSG lpMsg,
   return PeekMessage(lpMsg, hWnd, wMsgFilterMin, wMsgFilterMax, wRemoveMsg);
 }
 
+uint32_t WindowWin32::Win32MapVkToChar(uint32_t virtual_key) {
+  return MapVirtualKey(virtual_key, MAPVK_VK_TO_CHAR);
+}
+
 }  // namespace flutter

shell/platform/windows/window_win32.h

@@ -178,6 +178,11 @@ class WindowWin32 {
                                 UINT wMsgFilterMax,
                                 UINT wRemoveMsg);
 
+  // Win32's MapVirtualKey(*, MAPVK_VK_TO_CHAR).
+  //
+  // Used to process key messages. Exposed for dependency injection.
+  virtual uint32_t Win32MapVkToChar(uint32_t virtual_key);
+
  private:
   // Release OS resources associated with window.
   void Destroy();