From a0cd9e97850f8f8dfbdbca66c013021687f3cb82 Mon Sep 17 00:00:00 2001
From: Matej Knopp <matej.knopp@gmail.com>
Date: Wed, 7 Jul 2021 17:46:02 +0200
Subject: [PATCH] Do not expect WM_CHAR if control or windows key is pressed
 (flutter/engine#27064)

---
 .../shell/platform/windows/window_win32.cc    | 11 ++++++++--
 .../windows/window_win32_unittests.cc         | 22 +++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/engine/src/flutter/shell/platform/windows/window_win32.cc b/engine/src/flutter/shell/platform/windows/window_win32.cc
index 7b1e007afc9..4449915cde9 100644
--- a/engine/src/flutter/shell/platform/windows/window_win32.cc
+++ b/engine/src/flutter/shell/platform/windows/window_win32.cc
@@ -371,11 +371,18 @@ WindowWin32::HandleMessage(UINT const message,
       // Check if this key produces a character. If so, the key press should
       // be sent with the character produced at WM_CHAR. Store the produced
       // keycode (it's not accessible from WM_CHAR) to be used in WM_CHAR.
-      const unsigned int character = MapVirtualKey(wparam, MAPVK_VK_TO_CHAR);
-      if (character > 0 && is_keydown_message) {
+      //
+      // Messages with Control or Win modifiers down are never considered as
+      // 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);
+      if (character > 0 && is_keydown_message && GetKeyState(VK_CONTROL) == 0 &&
+          GetKeyState(VK_LWIN) == 0 && GetKeyState(VK_RWIN) == 0) {
         keycode_for_char_message_ = wparam;
         break;
       }
+      character = 0;
       unsigned int keyCode(wparam);
       const unsigned int scancode = (lparam >> 16) & 0xff;
       const bool extended = ((lparam >> 24) & 0x01) == 0x01;
diff --git a/engine/src/flutter/shell/platform/windows/window_win32_unittests.cc b/engine/src/flutter/shell/platform/windows/window_win32_unittests.cc
index 9680a0488bc..846c1217796 100644
--- a/engine/src/flutter/shell/platform/windows/window_win32_unittests.cc
+++ b/engine/src/flutter/shell/platform/windows/window_win32_unittests.cc
@@ -84,5 +84,27 @@ TEST(MockWin32Window, KeyDownPrintable) {
   window.InjectWindowMessage(WM_CHAR, 65, lparam);
 }
 
+TEST(MockWin32Window, KeyDownWithCtrl) {
+  MockWin32Window window;
+
+  // Simulate CONTROL pressed
+  BYTE keyboard_state[256];
+  memset(keyboard_state, 0, 256);
+  keyboard_state[VK_CONTROL] = -1;
+  SetKeyboardState(keyboard_state);
+
+  LPARAM lparam = CreateKeyEventLparam(30);
+
+  // Expect OnKey, but not OnText, because Control + Key is not followed by
+  // WM_CHAR
+  EXPECT_CALL(window, OnKey(65, 30, WM_KEYDOWN, 0, false, true)).Times(1);
+  EXPECT_CALL(window, OnText(_)).Times(0);
+
+  window.InjectWindowMessage(WM_KEYDOWN, 65, lparam);
+
+  memset(keyboard_state, 0, 256);
+  SetKeyboardState(keyboard_state);
+}
+
 }  // namespace testing
 }  // namespace flutter