win32: Fix composition UI being displayed when IME is disabled

src/video/windows/SDL_windowskeyboard.c

@@ -1072,6 +1072,14 @@ bool WIN_HandleIMEMessage(HWND hwnd, UINT msg, WPARAM wParam, LPARAM *lParam, SD
         *lParam &= element_mask;
 
         return false;
+    } else if (msg == WM_IME_STARTCOMPOSITION) {
+        SDL_DebugIMELog("WM_IME_STARTCOMPOSITION");
+        if (videodata->ime_internal_composition) {
+            // Windows may still display a composition dialog even with
+            // ISC_SHOWUICOMPOSITIONWINDOW cleared, so trap the message
+            // here to prevent that (even when the IME is disabled).
+            return true;
+        }
     }
 
     if (!videodata->ime_initialized || !videodata->ime_available || !videodata->ime_enabled) {
@@ -1099,12 +1107,6 @@ bool WIN_HandleIMEMessage(HWND hwnd, UINT msg, WPARAM wParam, LPARAM *lParam, SD
         SDL_DebugIMELog("WM_INPUTLANGCHANGE");
         IME_InputLangChanged(videodata);
         break;
-    case WM_IME_STARTCOMPOSITION:
-        SDL_DebugIMELog("WM_IME_STARTCOMPOSITION");
-        if (videodata->ime_internal_composition) {
-            trap = true;
-        }
-        break;
     case WM_IME_COMPOSITION:
         SDL_DebugIMELog("WM_IME_COMPOSITION %x", lParam);
         if (videodata->ime_internal_composition) {