/// <summary>
/// Helper method to find display index, header and header start position based on given mouse position
/// </summary>
private void FindDisplayIndexAndHeaderPosition(Point startPos, bool findNearestColumn, out int displayIndex, out Point headerPos, out DataGridColumnHeader header)
{
Debug.Assert(ParentDataGrid != null, "ParentDataGrid is null");
Point originPoint = new Point(0, 0);
headerPos = originPoint;
displayIndex = -1;
header = null;
if (startPos.X < 0.0)
{
if (findNearestColumn)
{
displayIndex = 0;
}
return;
}
double headerStartX = 0.0;
double headerEndX = 0.0;
int i = 0;
DataGrid dataGrid = ParentDataGrid;
double averageColumnWidth = dataGrid.InternalColumns.AverageColumnWidth;
bool firstVisibleNonFrozenColumnHandled = false;
for (i = 0; i < dataGrid.Columns.Count; i++)
{
displayIndex++;
DataGridColumnHeader currentHeader = dataGrid.ColumnHeaderFromDisplayIndex(i);
if (currentHeader == null)
{
DataGridColumn column = dataGrid.ColumnFromDisplayIndex(i);
if (!column.IsVisible)
{
continue;
}
else
{
headerStartX = headerEndX;
if (i >= dataGrid.FrozenColumnCount &&
!firstVisibleNonFrozenColumnHandled)
{
headerStartX -= dataGrid.HorizontalScrollOffset;
firstVisibleNonFrozenColumnHandled = true;
}
headerEndX = headerStartX + GetColumnEstimatedWidth(column, averageColumnWidth);
}
}
else
{
GeneralTransform transform = currentHeader.TransformToAncestor(this);
headerStartX = transform.Transform(originPoint).X;
headerEndX = headerStartX + currentHeader.RenderSize.Width;
}
if (DoubleUtil.LessThanOrClose(startPos.X, headerStartX))
{
break;
}
if (DoubleUtil.GreaterThanOrClose(startPos.X, headerStartX) &&
DoubleUtil.LessThanOrClose(startPos.X, headerEndX))
{
if (findNearestColumn)
{
double headerMidX = (headerStartX + headerEndX) * 0.5;
if (DoubleUtil.GreaterThanOrClose(startPos.X, headerMidX))
{
headerStartX = headerEndX;
displayIndex++;
}
if (_draggingSrcColumnHeader != null && _draggingSrcColumnHeader.Column != null && _draggingSrcColumnHeader.Column.DisplayIndex < displayIndex)
{
displayIndex--;
}
}
else
{
header = currentHeader;
}
break;
}
}
if (i == dataGrid.Columns.Count)
{
displayIndex = dataGrid.Columns.Count - 1;
headerStartX = headerEndX;
}
headerPos.X = headerStartX;
return;
}
