Feature Request: dynamic fitInsideVertically property for LineTouchTooltipData

fitInsideVertically is false by default. There are cases where the top most spot when shown a tooltip will get cut off by a different widget.

The problem with fitInsideVertically : true is all tooltips will be either centered or below from where the tap occurs. I still like the default behavior but the top most spot points should only have this property to true.

It would be nice to have some way to have fitInsideVertically: true only for the top y spots. Users can do their own logic on how much threshold they want to use.

Thoughts?

Begin at LineTouchTooltipData and trace the line-chart tooltip positioning behavior, especially how fitInsideVertically is applied. Clarify the threshold and expected placement for top versus other spots; done means the behavior is configurable without changing the default for other spots and the clipping case is covered by verification.

Written by the indexing model from the issue text.