//-------------------------------------------------------------------
// Calculate line advance distance. This functionality will go away
// when TextFormatter will be able to handle line height/stacking.
//
// lineHeight - calculated line height
//
// Returns: Line advance distance..
//-------------------------------------------------------------------
private double CalcLineAdvance(double lineHeight, LineProperties lineProperties)
{
return lineProperties.CalcLineAdvance(lineHeight);
}
// Performs one iteration of background measure.
// Background measure always works at the end of the current
// line metrics array -- invalidations to prevoiusly examined
// content is handled by incremental layout, synchronously.
//
// Returns the full content size, omitting any unanalyzed content
// at the document end.
private Size FullMeasureTick(double constraintWidth, LineProperties lineProperties)
{
Size desiredSize;
TextBoxLine line = new TextBoxLine(this);
int lineOffset;
bool endOfParagraph;
// Find the next position for this iteration.
if (_lineMetrics.Count == 0)
{
desiredSize = new Size();
lineOffset = 0;
}
else
{
desiredSize = _contentSize;
lineOffset = _lineMetrics[_lineMetrics.Count - 1].EndOffset;
}
// Calculate a stop time.
// We limit work to just a few milliseconds per iteration
// to avoid blocking the thread.
DateTime stopTime;
if ((ScrollBarVisibility)((Control)_host).GetValue(ScrollViewer.VerticalScrollBarVisibilityProperty) == ScrollBarVisibility.Auto)
{
// Workaround for bug 1766924.
// When VerticalScrollBarVisiblity == Auto, there's a problem with
// our interaction with ScrollViewer. Disable background layout to
// mitigate the problem until we can take a real fix in v.next.
//
stopTime = DateTime.MaxValue;
}
else
{
stopTime = DateTime.Now.AddMilliseconds(_maxMeasureTimeMs);
}
// Format lines until we hit the end of document or run out of time.
do
{
using (line)
{
line.Format(lineOffset, constraintWidth, constraintWidth, lineProperties, _cache.TextRunCache, _cache.TextFormatter);
// This is a loop invariant, but has negligable cost.
//
_lineHeight = lineProperties.CalcLineAdvance(line.Height);
_lineMetrics.Add(new LineRecord(lineOffset, line));
// Desired width is always max of calculated line widths.
// Desired height is sum of all line heights.
desiredSize.Width = Math.Max(desiredSize.Width, line.Width);
desiredSize.Height += _lineHeight;
lineOffset += line.Length;
endOfParagraph = line.EndOfParagraph;
}
}
while (!endOfParagraph && DateTime.Now < stopTime);
if (!endOfParagraph)
{
// Ran out of time. Defer to background layout.
SetFlags(true, Flags.BackgroundLayoutPending);
this.Dispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(OnBackgroundMeasure), null);
}
else
{
// Finished the entire document. Stop background layout.
SetFlags(false, Flags.BackgroundLayoutPending);
}
return desiredSize;
}
