public override void OnRender(Media.DrawingContext dc)
{
if (_lineCache == null || _lineCache.Count == 0)
{
return;
}
int nLines = _lineCache.Count;
int top = 0;
int width, height;
GetRenderSize(out width, out height);
// Draw each line of Text
//
int lineNumber = _currentLine;
while (lineNumber < nLines)
{
TextLine line = (TextLine)_lineCache[lineNumber];
if (top + line.Height > height)
{
break;
}
TextRun[] runs = line.Runs;
int x;
switch (_alignment)
{
case TextAlignment.Left:
x = 0;
break;
case TextAlignment.Center:
x = (width - line.Width) >> 1; // >> 1 is the same as div by 2
break;
case TextAlignment.Right:
x = width - line.Width;
break;
default:
throw new NotSupportedException();
}
for (int i = 0; i < runs.Length; i++)
{
TextRun run = runs[i];
int w, h;
run.GetSize(out w, out h);
int y = top + line.Baseline - run.Font.Ascent;
dc.DrawText(run.Text, run.Font, run.ForeColor, x, y);
x += w;
}
top += line.Height;
lineNumber++;
}
}
// Given an available width, takes the TextRuns and arranges them into
// separate lines, breaking where possible at whitespace.
//
internal ArrayList SplitLines(int availableWidth)
{
Debug.Assert(availableWidth > 0);
int lineWidth = 0;
ArrayList remainingRuns = new ArrayList();
for (int i = 0; i < TextRuns.Count; i++)
{
remainingRuns.Add(TextRuns[i]);
}
ArrayList lineCache = new ArrayList();
ArrayList runsOnCurrentLine = new ArrayList();
while (remainingRuns.Count > 0)
{
bool newLine = false;
TextRun run = (TextRun)remainingRuns[0];
remainingRuns.RemoveAt(0);
if (run.IsEndOfLine)
{
newLine = true;
}
else
{
// Add run to end of current line
//
int runWidth, runHeight;
run.GetSize(out runWidth, out runHeight);
lineWidth += runWidth;
runsOnCurrentLine.Add(run);
// If the line length now extends beyond the available width, attempt to break the line
//
if (lineWidth > availableWidth)
{
bool onlyRunOnCurrentLine = (runsOnCurrentLine.Count == 1);
if (run.Text.Length > 1)
{
runsOnCurrentLine.Remove(run);
TextRun run1, run2;
if (run.Break(runWidth - (lineWidth - availableWidth), out run1, out run2, onlyRunOnCurrentLine))
{
// Break and put overflow on next line
//
if (run1 != null)
{
runsOnCurrentLine.Add(run1);
}
if (run2 != null)
{
remainingRuns.Insert(0, run2);
}
}
else if (!onlyRunOnCurrentLine)
{
// No break found - put it on its own line
//
remainingRuns.Insert(0, run);
}
}
else // run.Text.Length == 1
{
if (!onlyRunOnCurrentLine)
{
runsOnCurrentLine.Remove(run);
remainingRuns.Insert(0, run);
}
}
newLine = true;
}
if (lineWidth >= availableWidth || remainingRuns.Count == 0)
{
newLine = true;
}
}
// If we're done with this line, add it to the list
//
if (newLine)
{
int lineHeight = 0;
int baseLine = 0;
int nRuns = runsOnCurrentLine.Count;
if (nRuns > 0)
{
// Compute line height & baseline
for (int i = 0; i < nRuns; i++)
{
Font font = ((TextRun)runsOnCurrentLine[i]).Font;
int h = font.Height + font.ExternalLeading;
if (h > lineHeight)
{
lineHeight = h;
baseLine = font.Ascent;
}
}
// Add line to cache
lineCache.Add(new TextLine(runsOnCurrentLine, lineHeight, baseLine));
}
else
{
// Empty line. Just borrow the height from the previous line, if any
lineHeight = (lineCache.Count) > 0 ?
((TextLine)lineCache[lineCache.Count - 1]).Height :
TextLine.DefaultLineHeight;
lineCache.Add(new TextLine(lineHeight));
}
// Move onto next line
//
runsOnCurrentLine.Clear();
lineWidth = 0;
}
}
return(lineCache);
}