} // ListViewUnloaded

        // ----------------------------------------------------------------------
        private void ThumbPreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (!(sender is Thumb thumb))
            {
                return;
            }
            var gridViewColumn = FindParentColumn(thumb);

            if (gridViewColumn == null)
            {
                return;
            }

            // suppress column resizing for proportional, fixed and range fill columns
            if (ProportionalColumn.IsProportionalColumn(gridViewColumn) || FixedColumn.IsFixedColumn(gridViewColumn) || IsFillColumn(gridViewColumn))
            {
                thumb.Cursor = null;
                return;
            }

            // check range column bounds
            if (thumb.IsMouseCaptured && RangeColumn.IsRangeColumn(gridViewColumn))
            {
                var minWidth = RangeColumn.GetRangeMinWidth(gridViewColumn);
                var maxWidth = RangeColumn.GetRangeMaxWidth(gridViewColumn);

                if (minWidth.HasValue && maxWidth.HasValue && minWidth > maxWidth)
                {
                    return;                                                                // invalid case
                }
                if (_resizeCursor == null)
                {
                    _resizeCursor = thumb.Cursor;                        // save the resize cursor
                }
                if (minWidth.HasValue && gridViewColumn.Width <= minWidth.Value)
                {
                    thumb.Cursor = Cursors.No;
                }
                else if (maxWidth.HasValue && gridViewColumn.Width >= maxWidth.Value)
                {
                    thumb.Cursor = Cursors.No;
                }
                else
                {
                    thumb.Cursor = _resizeCursor; // between valid min/max
                }
            }
        } // ThumbPreviewMouseMove
        } // ThumbPreviewMouseMove

        // ----------------------------------------------------------------------
        private void ThumbPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            var thumb          = (Thumb)sender;
            var gridViewColumn = FindParentColumn(thumb);

            if (gridViewColumn == null)
            {
                throw new InvalidOperationException("Could not find parent column");
            }

            // suppress column resizing for proportional, fixed and range fill columns
            if (ProportionalColumn.IsProportionalColumn(gridViewColumn) || FixedColumn.IsFixedColumn(gridViewColumn) || IsFillColumn(gridViewColumn))
            {
                e.Handled = true;
            }
        } // ThumbPreviewMouseLeftButtonDown
        } // Refresh

        // ----------------------------------------------------------------------
        private void RegisterEvents(DependencyObject start)
        {
            for (var i = 0; i < VisualTreeHelper.GetChildrenCount(start); i++)
            {
                var childVisual = (Visual)VisualTreeHelper.GetChild(start, i);
                if (childVisual is Thumb thumb)
                {
                    var gridViewColumn = FindParentColumn(childVisual);
                    if (gridViewColumn != null)
                    {
                        if (ProportionalColumn.IsProportionalColumn(gridViewColumn) || FixedColumn.IsFixedColumn(gridViewColumn) ||
                            IsFillColumn(gridViewColumn))
                        {
                            thumb.IsHitTestVisible = false;
                        }
                        else
                        {
                            thumb.PreviewMouseMove           += ThumbPreviewMouseMove;
                            thumb.PreviewMouseLeftButtonDown += ThumbPreviewMouseLeftButtonDown;
                            DependencyPropertyDescriptor.FromProperty(GridViewColumn.WidthProperty, typeof(GridViewColumn))
                            .AddValueChanged(gridViewColumn, GridColumnWidthChanged);
                        }
                    }
                }
                else if (childVisual is GridViewColumnHeader columnHeader)
                {
                    columnHeader.SizeChanged += GridColumnHeaderSizeChanged;
                }
                else if (_scrollViewer == null && childVisual is ScrollViewer)
                {
                    _scrollViewer = (ScrollViewer)childVisual;
                    _scrollViewer.ScrollChanged += ScrollViewerScrollChanged;
                    // assume we do the regulation of the horizontal scrollbar
                    _scrollViewer.HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden;
                    _scrollViewer.VerticalScrollBarVisibility   = VerticalScrollBarVisibility;
                }

                RegisterEvents(childVisual); // recursive
            }
        } // RegisterEvents
        } // ThumbPreviewMouseLeftButtonDown

        // ----------------------------------------------------------------------
        private void GridColumnWidthChanged(object sender, EventArgs e)
        {
            if (!_loaded)
            {
                return;
            }

            var gridViewColumn = (GridViewColumn)sender;

            if (gridViewColumn == null)
            {
                throw new ArgumentNullException(nameof(sender));
            }

            // suppress column resizing for proportional and fixed columns
            if (ProportionalColumn.IsProportionalColumn(gridViewColumn) || FixedColumn.IsFixedColumn(gridViewColumn))
            {
                return;
            }

            // ensure range column within the bounds
            if (RangeColumn.IsRangeColumn(gridViewColumn))
            {
                // special case: auto column width - maybe conflicts with min/max range
                if (gridViewColumn.Width.Equals(double.NaN))
                {
                    _autoSizedColumn = gridViewColumn;
                    return; // handled by the change header size event
                }

                // ensure column bounds
                if (Math.Abs(SetRangeColumnToBounds(gridViewColumn) - 0) > ZeroWidthRange)
                {
                    return;
                }
            }

            DoResizeColumns();
        } // GridColumnWidthChanged
        } // RegisterEvents

        // ----------------------------------------------------------------------
        private void UnregisterEvents(DependencyObject start)
        {
            for (var i = 0; i < VisualTreeHelper.GetChildrenCount(start); i++)
            {
                var childVisual = (Visual)VisualTreeHelper.GetChild(start, i);
                if (childVisual is Thumb)
                {
                    var gridViewColumn = FindParentColumn(childVisual);
                    if (gridViewColumn != null)
                    {
                        var thumb = (Thumb)childVisual;
                        if (ProportionalColumn.IsProportionalColumn(gridViewColumn) || FixedColumn.IsFixedColumn(gridViewColumn) ||
                            IsFillColumn(gridViewColumn))
                        {
                            thumb.IsHitTestVisible = true;
                        }
                        else
                        {
                            thumb.PreviewMouseMove           -= ThumbPreviewMouseMove;
                            thumb.PreviewMouseLeftButtonDown -= ThumbPreviewMouseLeftButtonDown;
                            DependencyPropertyDescriptor.FromProperty(GridViewColumn.WidthProperty, typeof(GridViewColumn))
                            .RemoveValueChanged(gridViewColumn, GridColumnWidthChanged);
                        }
                    }
                }
                else if (childVisual is GridViewColumnHeader columnHeader)
                {
                    columnHeader.SizeChanged -= GridColumnHeaderSizeChanged;
                }
                else if (_scrollViewer == null && childVisual is ScrollViewer viewer)
                {
                    _scrollViewer = viewer;
                    _scrollViewer.ScrollChanged -= ScrollViewerScrollChanged;
                }

                UnregisterEvents(childVisual); // recursive
            }
        } // UnregisterEvents
        } // InitColumns

        // ----------------------------------------------------------------------
        protected virtual void ResizeColumns()
        {
            if (!(ListView.View is GridView view) || view.Columns.Count == 0)
            {
                return;
            }

            // listview width
            var actualWidth = double.PositiveInfinity;

            if (_scrollViewer != null)
            {
                actualWidth = _scrollViewer.ViewportWidth;
            }
            if (double.IsInfinity(actualWidth))
            {
                actualWidth = ListView.ActualWidth;
            }
            if (double.IsInfinity(actualWidth) || actualWidth <= 0)
            {
                return;
            }

            double resizeableRegionCount = 0;
            double otherColumnsWidth     = 0;

            // determine column sizes
            foreach (var gridViewColumn in view.Columns)
            {
                if (ProportionalColumn.IsProportionalColumn(gridViewColumn))
                {
                    var proportionalWidth = ProportionalColumn.GetProportionalWidth(gridViewColumn);
                    if (proportionalWidth != null)
                    {
                        resizeableRegionCount += proportionalWidth.Value;
                    }
                }
                else
                {
                    otherColumnsWidth += gridViewColumn.ActualWidth;
                }
            }

            if (resizeableRegionCount <= 0)
            {
                // no proportional columns present: commit the regulation to the scroll viewer
                if (_scrollViewer != null)
                {
                    _scrollViewer.HorizontalScrollBarVisibility = ScrollBarVisibility.Auto;
                }

                // search the first fill column
                GridViewColumn?fillColumn = null;
                for (var i = 0; i < view.Columns.Count; i++)
                {
                    var gridViewColumn = view.Columns[i];
                    if (IsFillColumn(gridViewColumn))
                    {
                        fillColumn = gridViewColumn;
                        break;
                    }
                }

                if (fillColumn != null)
                {
                    var otherColumnsWithoutFillWidth = otherColumnsWidth - fillColumn.ActualWidth;
                    var fillWidth = actualWidth - otherColumnsWithoutFillWidth;
                    if (fillWidth > 0)
                    {
                        var minWidth = RangeColumn.GetRangeMinWidth(fillColumn);
                        var maxWidth = RangeColumn.GetRangeMaxWidth(fillColumn);

                        var setWidth = !(minWidth.HasValue && fillWidth < minWidth.Value);
                        if (maxWidth.HasValue && fillWidth > maxWidth.Value)
                        {
                            setWidth = false;
                        }
                        if (setWidth)
                        {
                            if (_scrollViewer != null)
                            {
                                _scrollViewer.HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden;
                            }
                            fillColumn.Width = fillWidth;
                        }
                    }
                }

                return;
            }

            var resizeableColumnsWidth = actualWidth - otherColumnsWidth;

            if (resizeableColumnsWidth <= 0)
            {
                return;                              // missing space
            }
            // resize columns
            var resizeableRegionWidth = resizeableColumnsWidth / resizeableRegionCount;

            foreach (var gridViewColumn in view.Columns)
            {
                if (ProportionalColumn.IsProportionalColumn(gridViewColumn))
                {
                    var proportionalWidth = ProportionalColumn.GetProportionalWidth(gridViewColumn);
                    if (proportionalWidth != null)
                    {
                        gridViewColumn.Width = proportionalWidth.Value * resizeableRegionWidth;
                    }
                }
            }
        } // ResizeColumns