// Determine where each grapheme (essentially character) will go when drawing text along a path.
// The algorithm for how text is laid out along a path makes sense, with one MAJOR weirdness.
// The basic algorithm is that the width of each character to draw is determined. Starting where the last
// character ends, the path is followed for that character width (around corners if needed), and the point along
// the path at that point is connected to the start point of the character with a line. The character is drawn along that
// baseline, starting at the start point. The end point is used as the start of the next character. If there are bends,
// of course, the character won't end right at that end point, but we ignore that.
//
// THe weirdness is this: instead of measuring distance along the path correctly with the Pythagorian formula, a
// strange alternate metric of dx + 1/2 dy is used, where dx is the larger ordinate delta and dy is the smaller ordinate
// delta. Thus, text along diagonals is squished together more than it should be. I have no explanation as to why
// this might work but it reproduces what OCAD does. See the function "BizzarroDistance" in SymPath.
private List<GraphemePlacement> GetLineTextGraphemePlacement(SymPath path, string text)
{
float totalWidth = 0;
List<GraphemePlacement> graphemeList = new List<GraphemePlacement>();
float pathLength = path.BizzarroLength;
if (pathLength == 0)
return graphemeList; // nothing to draw.
// First, determine all the graphemes and their width
TextElementEnumerator enumerator = StringInfo.GetTextElementEnumerator(text);
while (enumerator.MoveNext()) {
string grapheme = enumerator.GetTextElement();
float graphemeWidth;
if (grapheme == " ")
graphemeWidth = wordSpacing * spaceWidth;
else {
float width = MeasureStringWidth(grapheme);
graphemeWidth = width + charSpacing * spaceWidth;
}
graphemeList.Add(new GraphemePlacement(grapheme, graphemeWidth, new PointF(), 0));
totalWidth += graphemeWidth;
if (totalWidth + 0.01F >= pathLength && fontAlign != TextSymDefAlignment.Justified)
break; // We don't have any room for more characters. (0.01 prevents a very small tail at the end.)
}
// For OCAD compatibility, truncate right aligned text if too big to fit so the whole
// string fits. (Note that left-aligned text will typically show one more character than this.)
if (pathLength < totalWidth && fontAlign != TextSymDefAlignment.Left && fontAlign != TextSymDefAlignment.Justified) {
totalWidth -= graphemeList[graphemeList.Count - 1].width;
if (fontAlign == TextSymDefAlignment.Right)
graphemeList.RemoveAt(graphemeList.Count - 1);
}
// Where does the text begin?
float startingDistance = 0;
if (fontAlign == TextSymDefAlignment.Left || fontAlign == TextSymDefAlignment.Justified)
startingDistance = 0;
else if (fontAlign == TextSymDefAlignment.Right)
startingDistance = pathLength - totalWidth;
else if (fontAlign == TextSymDefAlignment.Center)
startingDistance = (pathLength - totalWidth) / 2;
// For justified (all-line) text, adjust the widths of each character so they all fit.
if (fontAlign == TextSymDefAlignment.Justified && graphemeList.Count > 1) {
if (charSpacing > 0) {
// last character doesn't have space added.
GraphemePlacement graphemePlacement = graphemeList[graphemeList.Count - 1];
graphemePlacement.width -= charSpacing * spaceWidth;
totalWidth -= charSpacing * spaceWidth;
graphemeList[graphemeList.Count - 1] = graphemePlacement;
}
float adjustment = (pathLength - totalWidth) / (graphemeList.Count - 1);
for (int i = 0; i < graphemeList.Count - 1; ++i) {
GraphemePlacement graphemePlacement = graphemeList[i];
graphemePlacement.width += adjustment;
graphemeList[i] = graphemePlacement;
}
}
// Find points along the path that are the start/end of each grapheme.
PointF[] points = new PointF[graphemeList.Count + 1];
float curDistance = startingDistance;
for (int i = 0; i < graphemeList.Count; ++i) {
points[i] = path.PointAtLengthBizzarro(curDistance);
curDistance += graphemeList[i].width;
}
points[graphemeList.Count] = path.PointAtLengthBizzarro(Math.Min(curDistance, pathLength));
// Fill in graphemeList with start points and angles
for (int i = 0; i < graphemeList.Count; ++i) {
GraphemePlacement graphemePlacement = graphemeList[i];
graphemePlacement.pointStart = points[i];
float distX = points[i + 1].X - points[i].X;
float distY = points[i + 1].Y - points[i].Y;
graphemePlacement.angle = (float) (Math.Atan2(distY, distX) * 360.0 / (Math.PI * 2));
graphemeList[i] = graphemePlacement;
}
return graphemeList;
}