What feedback is given to users when a widget is invalid?

When a widget is invalid, providing a validation error message when the input gains focus is an effective way to inform users that there is an issue that needs their attention. This approach ensures that the user is immediately aware of the problem as they interact with the input field, enhancing the overall user experience.

By showing the validation error message upon gaining focus, users receive prompt feedback, allowing them to correct their input right away. This method also helps in preventing frustration, as users are guided through the corrections seamlessly.

In contrast, other options lack this immediacy or clarity. For example, simply deleting the widget does not provide any feedback to the user about what went wrong or how to correct it. A success message only provides positive feedback and does not inform the user of any errors. A validation error message when clicked might not always capture the user's attention immediately, especially if they do not realize they need to click on the widget first to see the message. Thus, showing the validation error message on focus is the most effective method for user engagement and error handling.