The current legality widget does not count down flight/block time remaining for the day until you start to exceed the scheduled block for the leg. So if you have a long taxi it will still show you legal to take off even if your not.
A widget that takes previous block for the day, then begins to add by the minute from the block out of your current flight and displays time remaining will enable you to see if there is enough time left after a long ground delay to complete that flight legally for that day. You would have to enter the block out manually.