WPF FlowDocument: force calculation of height etc. "off screen"
- by Lars
My target: a DocumentPaginator which takes a FlowDocument with a table, which splits the table to fit the pagesize and repeat the header/footer (special tagged TableRowGroups) on every page.
For splitting the table I have to know the heights of its rows.
While building the FlowDocument-table by code, the height/width of the TableRows are 0 (of course). If I assign this document to a FlowDocumentScrollViewer (PageSize is set), the heights etc. are calculated. Is this possible without using an UI-bound object? Instantiating a FlowDocumentScrollViewer which is not bound to a window doesn't force the pagination/calculation of the heights.
This is how I determine the height of a TableRow (which works perfectly for documents shown by a FlowDocumentScrollViewer):
FlowDocument doc = BuildNewDocument();
// what is the scrollviewer doing with the FlowDocument?
FlowDocumentScrollViewer dv = new FlowDocumentScrollViewer();
dv.Document = doc;
dv.Arrange(new Rect(0, 0, 0, 0));
TableRowGroup dataRows = null;
foreach (Block b in doc.Blocks)
{
if (b is Table)
{
Table t = b as Table;
foreach (TableRowGroup g in t.RowGroups)
{
if ((g.Tag is String) && ((String)g.Tag == "dataRows"))
{
dataRows = g;
break;
}
}
}
if (dataRows != null)
break;
}
if (dataRows != null)
{
foreach (TableRow r in dataRows.Rows)
{
double maxCellHeight = 0.0;
foreach (TableCell c in r.Cells)
{
Rect start = c.ElementStart.GetCharacterRect(LogicalDirection.Forward);
Rect end = c.ElementEnd.GetNextInsertionPosition(LogicalDirection.Backward).GetCharacterRect(LogicalDirection.Forward);
double cellHeight = end.Bottom - start.Top;
if (cellHeight > maxCellHeight)
maxCellHeight = cellHeight;
}
System.Diagnostics.Trace.WriteLine("row " + dataRows.Rows.IndexOf(r) + " = " + maxCellHeight);
}
}
Edit:
I added the FlowDocumentScrollViewer to my example. The call of "Arrange" forces the FlowDocument to calculate its heights etc. I would like to know, what the FlowDocumentScrollViewer is doing with the FlowDocument, so I can do it without the UIElement. Is it possible?
