fix(windows): Add review suggestions

Co-authored-by: Marc Durdin <marc@durdin.net>

windows/src/engine/keyman32/k32_globals.cpp

@@ -72,8 +72,8 @@
 UINT
   //TODO: consolidate these messages -- they are probably not all required now
   wm_keyman = 0,						// user message - ignore msg   // I3594
-  wm_keyman_keyevent = 0,   // for serialized input
-  wm_keyman_modifierevent = 0,
+  wm_keyman_keyevent = 0,      // for serialized input
+  wm_keyman_modifierevent = 0, // for serialized input
 	wm_kmdebug = 0,						//  " "  "  "   - debugging
 
 	wm_keymankeydown = 0,

windows/src/engine/keyman32/k32_lowlevelkeyboardhook.cpp

@@ -202,6 +202,10 @@ LRESULT _kmnLowLevelKeyboardProc(
     if(isUp) FHotkeyShiftState &= ~Flag;
     else FHotkeyShiftState |= Flag;
     // #7337 Post the modifier state ensuring the serialized queue is in sync
+    // Note that the modifier key may be posted again with wm_keyman_keyevent,
+    // later in this function. This is intentional, as the wm_keyman_modifier 
+    // event message only updates our internal modifier state, and does not do 
+    // any additional processing or other serialization of the input queue.
     if (flag_ShouldSerializeInput) {
       PostMessage(ISerialKeyEventServer::GetServer()->GetWindow(), wm_keyman_modifierevent, hs->vkCode, LLKHFFlagstoWMKeymanKeyEventFlags(hs));
     }

windows/src/engine/keyman32/serialkeyeventserver.cpp

@@ -485,7 +485,10 @@ private:
         input[1].ki.dwExtraInfo = EXTRAINFO_FLAG_SERIALIZED_USER_KEY_EVENT;
         input[1].ki.dwFlags = lParam & 0xFFFF;
 
-        if (msg == wm_keyman_keyevent){
+        if (msg == wm_keyman_keyevent) {
+          // We track changes to modifiers with wm_keyman_modifierevent, but only ever
+          // pass them on to the app when we receive them with the wm_keyman_keyevent 
+          // message.
           if (!SendInput(2, input, sizeof(INPUT))) {
             DebugLastError("SendInput");
           }