From 141779be1d7ce5efcba013c5a9609c9397f7516c Mon Sep 17 00:00:00 2001
From: barrelltitor <barrelltitor@barrelltitor-laptop.tail717f6c.ts.net>
Date: Sat, 8 Aug 2026 21:29:12 +0300
Subject: [PATCH] fix: resync Windows keys from low-level hook state

---
 src/lib/platform/MSWindowsHook.cpp     | 31 +++++++++++++++++++++-----
 src/lib/platform/MSWindowsHook.h       |  3 +++
 src/lib/platform/MSWindowsKeyState.cpp |  4 +++-
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/lib/platform/MSWindowsHook.cpp b/src/lib/platform/MSWindowsHook.cpp
index 9c849847d..05a7b82ea 100644
--- a/src/lib/platform/MSWindowsHook.cpp
+++ b/src/lib/platform/MSWindowsHook.cpp
@@ -10,6 +10,9 @@
 #include "base/Log.h"
 #include "deskflow/ScreenException.h"
 
+#include <cstring>
+#include <mutex>
+
 #ifndef WM_MOUSEHWHEEL
 #define WM_MOUSEHWHEEL 0x020E
 #endif
@@ -34,6 +37,8 @@ static WPARAM g_deadRelease = 0;
 static LPARAM g_deadLParam = 0;
 static BYTE g_deadKeyState[256] = {0};
 static BYTE g_keyState[256] = {0};
+static bool g_keyStateValid = false;
+static std::mutex g_keyStateMutex;
 static DWORD g_hookThread = 0;
 static bool g_fakeServerInput = false;
 static BOOL g_isPrimary = TRUE;
@@ -142,6 +147,15 @@ void MSWindowsHook::setMode(EHookMode mode)
   g_mode = mode;
 }
 
+bool MSWindowsHook::getPhysicalKeyState(BYTE keys[256])
+{
+  std::lock_guard<std::mutex> lock(g_keyStateMutex);
+  if (g_keyStateValid) {
+    std::memcpy(keys, g_keyState, sizeof(g_keyState));
+  }
+  return g_keyStateValid;
+}
+
 static void keyboardGetState(BYTE keys[256], DWORD vkCode, bool kf_up)
 {
   // we have to use GetAsyncKeyState() rather than GetKeyState() because
@@ -152,6 +166,8 @@ static void keyboardGetState(BYTE keys[256], DWORD vkCode, bool kf_up)
     return;
   }
 
+  std::lock_guard<std::mutex> lock(g_keyStateMutex);
+
   // Keep track of key state on our own in case GetAsyncKeyState() fails
   g_keyState[vkCode] = kf_up ? 0 : 0x80;
   g_keyState[VK_SHIFT] = g_keyState[VK_LSHIFT] | g_keyState[VK_RSHIFT];
@@ -179,6 +195,7 @@ static void keyboardGetState(BYTE keys[256], DWORD vkCode, bool kf_up)
 
   key = GetKeyState(VK_CAPITAL);
   keys[VK_CAPITAL] = (BYTE)(((key < 0) ? 0x80 : 0) | (key & 1));
+  g_keyStateValid = true;
 }
 
 static WPARAM makeKeyMsg(UINT virtKey, WCHAR wc, bool noAltGr)
@@ -240,17 +257,17 @@ static bool keyboardHookHandler(WPARAM wParam, LPARAM lParam)
   // tell server about event
   PostThreadMessage(g_threadID, DESKFLOW_MSG_DEBUG, wParam, lParam);
 
-  // ignore dead key release
+  // we need the keyboard state for ToAscii()
+  BYTE keys[256];
+  keyboardGetState(keys, vkCode, kf_up);
+
+  // Update the physical state before ignoring a dead key release so it cannot remain down in the resync snapshot.
   if ((g_deadVirtKey == wParam || g_deadRelease == wParam) && (lParam & 0x80000000u) != 0) {
     g_deadRelease = 0;
     PostThreadMessage(g_threadID, DESKFLOW_MSG_DEBUG, wParam | 0x04000000, lParam);
     return false;
   }
 
-  // we need the keyboard state for ToAscii()
-  BYTE keys[256];
-  keyboardGetState(keys, vkCode, kf_up);
-
   // ToAscii() maps ctrl+letter to the corresponding control code
   // and ctrl+backspace to delete.  we don't want those translations
   // so clear the control modifier state.  however, if we want to
@@ -671,6 +688,10 @@ int MSWindowsHook::uninstall()
     g_getMessage = nullptr;
   }
 
+  std::lock_guard<std::mutex> lock(g_keyStateMutex);
+  std::memset(g_keyState, 0, sizeof(g_keyState));
+  g_keyStateValid = false;
+
   return 1;
 }
 
diff --git a/src/lib/platform/MSWindowsHook.h b/src/lib/platform/MSWindowsHook.h
index e767d8790..a96a7295c 100644
--- a/src/lib/platform/MSWindowsHook.h
+++ b/src/lib/platform/MSWindowsHook.h
@@ -62,6 +62,9 @@ public:
 
   void setMode(EHookMode mode);
 
+  //! Copy the hook's physical key state; false until it has observed an event.
+  static bool getPhysicalKeyState(BYTE keys[256]);
+
   static EHookResult install();
 
   static int uninstall();
diff --git a/src/lib/platform/MSWindowsKeyState.cpp b/src/lib/platform/MSWindowsKeyState.cpp
index b42ca8547..efaa54708 100644
--- a/src/lib/platform/MSWindowsKeyState.cpp
+++ b/src/lib/platform/MSWindowsKeyState.cpp
@@ -13,6 +13,7 @@
 #include "common/Constants.h"
 #include "platform/MSWindowsDesks.h"
 #include "platform/MSWindowsHandle.h"
+#include "platform/MSWindowsHook.h"
 
 // extended mouse buttons
 #if !defined(VK_XBUTTON1)
@@ -844,7 +845,8 @@ int32_t MSWindowsKeyState::pollActiveGroup() const
 void MSWindowsKeyState::pollPressedKeys(KeyButtonSet &pressedKeys) const
 {
   BYTE keyState[256];
-  if (!GetKeyboardState(keyState)) {
+  // The caller's GetKeyboardState queue can lag the low-level hook during a screen switch.
+  if (!MSWindowsHook::getPhysicalKeyState(keyState) && !GetKeyboardState(keyState)) {
     LOG_WARN("keyboard state is unexpected");
     LOG_DEBUG("function 'GetKeyboardState' returned false on 'pollPressedKeys'");
     return;