TVirtualDrawTree.OnGetCellIsEmpty Event

Triggered when the tree control needs to know whether a given column is empty.

property OnGetCellIsEmpty: TVTGetCellIsEmptyEvent;

Virtual Treeview supports the concept of column spanning where one cell with too much text to fit into its own space can expand to the right cell neighbors if they are empty. To make this work it is necessary to know if a cell is considered as being empty, whatever this means to an application. The string tree descendant simply checks the text for the given cell and calls back its ancestor if there is no text to further refine if the cell must stay as if it contained something. The ancestor (TBaseVirtualTree) now triggers OnGetCellIsEmpty to let the application decide.

TVirtualDrawTree Class