Fix the issue where the language bar and FTB are out of sync for the Chinese-Japanese status.

src/IME/MetasequoiaIME.cpp

@@ -2399,6 +2399,10 @@ LRESULT CALLBACK CMetasequoiaIME_WindowProc(HWND hWnd, UINT message, WPARAM wPar
         break;
     }
     case WM_ThreadFocus: {
+        // Some Chromium/Electron window switches surface only as thread-focus
+        // changes. Refresh this thread's cached TSF language-bar item even when
+        // there was no document-focus transition.
+        pIME->_RefreshLanguageBarThemeIcons();
         SendCurrentImeStatusSnapshot(pIME);
         break;
     }

src/LanguageBar/LanguageBar.cpp

@@ -109,7 +109,19 @@ void CMetasequoiaIME::_UpdateLanguageBarOnSetFocus(_In_ ITfDocumentMgr *pDocMgrF
     CCompositionProcessorEngine *pCompositionProcessorEngine = nullptr;
     pCompositionProcessorEngine = _pCompositionProcessorEngine;
 
-    pCompositionProcessorEngine->SetLanguageBarStatus(TF_LBI_STATUS_DISABLED, needDisableButtons);
+    pCompositionProcessorEngine->SetLanguageBarStatus(TF_LBI_STATUS_DISABLED, needDisableButtons);
+
+    // SetStatus intentionally keeps the item enabled when focus is absent so
+    // Firefox does not replace our mode glyph with its disabled/close glyph.
+    // Consequently, returning to a document may not change the status bits and
+    // therefore may not generate an ITfLangBarItemSink update.  Always refresh
+    // the newly focused thread's item: Windows caches each host/thread's icon,
+    // and another host may have changed the shared Chinese/Japanese mode while
+    // this one was in the background.
+    if (!needDisableButtons)
+    {
+        pCompositionProcessorEngine->RefreshLanguageBarIcons();
+    }
 }
 
 //+---------------------------------------------------------------------------