tableview.go
func (l *TableView) OnBeforeDraw(fn func(int, int, int, int)) {
	l.mtx.Lock()
	l.onBeforeDraw = fn
	l.mtx.Unlock()
}
func (l *TableView) OnBeforeDraw(fn func(int, int, int, int)) {
	l.mtx.Lock()
	l.onBeforeDraw = fn
	l.mtx.Unlock()
}
func ( l * TableView ) OnBeforeDraw ( fn func ( int , int , int , int ) ) { l . mtx . Lock ( ) l . onBeforeDraw = fn l . mtx . Unlock ( ) }
// OnBeforeDraw is called when TableView is going to draw its cells.
// Can be used to precache the data, and make OnDrawCell faster.
// Callback receives 4 arguments: first visible column, first visible row,
// the number of visible columns, the number of visible rows
OnBeforeDraw is called when TableView is going to draw its cells . Can be used to precache the data and make OnDrawCell faster . Callback receives 4 arguments : first visible column first visible row the number of visible columns the number of visible rows