[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'ComCtrls' (#lcl)

# TCustomTreeView.OnCollapsing

OnCollapsing - specialised event handler while part of the tree is being collapsed

## Declaration

Source position: comctrls.pp line 2399

`protected property TCustomTreeView.OnCollapsing: TTVCollapsingEvent read FOnCollapsing write FOnCollapsing;`

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