Make CJK imes work better

Dalamud/Interface/Utility/ImGuiHelpers.cs

@@ -426,6 +426,26 @@ public static class ImGuiHelpers
     /// <param name="ptr">The pointer.</param>
     /// <returns>Whether it is empty.</returns>
     public static unsafe bool IsNull(this ImFontAtlasPtr ptr) => ptr.NativePtr == null;
+    
+    /// <summary>
+    /// Finds the corresponding ImGui viewport ID for the given window handle.
+    /// </summary>
+    /// <param name="hwnd">The window handle.</param>
+    /// <returns>The viewport ID, or -1 if not found.</returns>
+    internal static unsafe int FindViewportId(nint hwnd)
+    {
+        if (!IsImGuiInitialized)
+            return -1;
+
+        var viewports = new ImVectorWrapper<ImGuiViewportPtr>(&ImGui.GetPlatformIO().NativePtr->Viewports);
+        for (var i = 0; i < viewports.LengthUnsafe; i++)
+        {
+            if (viewports.DataUnsafe[i].PlatformHandle == hwnd)
+                return i;
+        }
+
+        return -1;
+    }
 
     /// <summary>
     /// Get data needed for each new frame.