There is no way to detect that the chart has been maximized.
One way to achieve this is to create two instances of the chart, one normal and one maximized, and use conditional show using a button to control which one is visible. Or make the number of bars based on a variable to allow the user to select between 5 and 20 bars (using a slider, input box or toggle values using one or two buttons.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein