This function should almost never be used.
Accessibility does not need the function anymore.
It is meant for private use by ATK for determining the number of visible children that are removed when the user collapses a row, or a row is deleted.
| this |
A TreeView |
| func |
Function to be called when a view row is destroyed, or null |
| data |
User data to be passed to |
| destroy |
Destroy notifier for |