msctf: Define ITfTextInputProcessor. Implemented by the Text Services.

include/msctf.idl

@@ -471,3 +471,18 @@ interface IEnumTfLanguageProfiles : IUnknown
     HRESULT Skip(
         [in] ULONG ulCount);
 };
+
+[
+  object,
+  local,
+  uuid(aa80e7f7-2021-11d2-93e0-0060b067b86e),
+  pointer_default(unique)
+]
+interface ITfTextInputProcessor : IUnknown
+{
+    HRESULT Activate(
+        [in] ITfThreadMgr *ptim,
+        [in] TfClientId tid);
+
+    HRESULT Deactivate();
+};