How to know current editing state of TextEditor.

You can use CAknEnv::EditingStateIndicator() to get then current editing starts.
code below show how to know if T9 is On or OFF.

TBool t9_mode;
MAknEditingStateIndicator* editingindicator = CAknEnv::Static()->EditingStateIndicator();
CAknIndicatorContainer* indicatorcontainer =editingindicator->IndicatorContainer();
if (indicatorcontainer->IndicatorState(TUid::Uid(EAknNaviPaneEditorIndicatorT9)))
  {
  t9_mode = ETrue;
  }
else
  {
  t9_mode = EFalse;
  }