static List <Curve2DSample> _computeSamples(List <Offset> controlPoints, float?tension)
{
List <Offset> _controlPoints = new List <Offset>();
_controlPoints.Add(Offset.zero);
_controlPoints.AddRange(controlPoints);
_controlPoints.Add(new Offset(1.0f, 1.0f));
return(CatmullRomSpline.precompute(_controlPoints, tension: tension).generateSamples(
start: 0.0f, end: 1.0f, tolerance: 1e-12f).ToList());
}
static bool validateControlPoints(
List <Offset> controlPoints,
float?tension = 0.0f,
List <string> reasons = null)
{
D.assert(tension != null);
if (controlPoints == null)
{
D.assert(() => {
reasons?.Add("Supplied control points cannot be null");
return(true);
});
return(false);
}
if (controlPoints.Count < 2)
{
D.assert(() => {
reasons?.Add("There must be at least two points supplied to create a valid curve.");
return(true);
});
return(false);
}
List <Offset> _controlPoints = new List <Offset>();
_controlPoints.AddRange(controlPoints);
_controlPoints.Insert(0, Offset.zero);
_controlPoints.Add(new Offset(1.0f, 1.0f));
Offset startHandle = _controlPoints[0] * 2.0f - _controlPoints[1];
Offset endHandle = _controlPoints.last() * 2.0f - _controlPoints[_controlPoints.Count - 2];
_controlPoints.Insert(0, startHandle);
_controlPoints.Add(endHandle);
float lastX = -float.PositiveInfinity;
for (int i = 0; i < _controlPoints.Count; ++i)
{
if (i > 1 &&
i < _controlPoints.Count - 2 &&
(_controlPoints[i].dx <= 0.0f || _controlPoints[i].dx >= 1.0f))
{
D.assert(() => {
reasons?.Add("Control points must have X values between 0.0 and 1.0, exclusive. " +
$"Point {i} has an x value ({_controlPoints[i].dx}) which is outside the range.");
return(true);
});
return(false);
}
if (_controlPoints[i].dx <= lastX)
{
D.assert(() => {
reasons?.Add("Each X coordinate must be greater than the preceding X coordinate " +
$"(i.e. must be monotonically increasing in X). Point {i} has an x value of " +
$"{_controlPoints[i].dx}, which is not greater than {lastX}");
return(true);
});
return(false);
}
lastX = _controlPoints[i].dx;
}
bool success = true;
lastX = -float.PositiveInfinity;
const float tolerance = 1e-3f;
CatmullRomSpline testSpline = new CatmullRomSpline(_controlPoints, tension: tension);
float start = testSpline.findInverse(0.0f);
float end = testSpline.findInverse(1.0f);
IEnumerable <Curve2DSample> samplePoints = testSpline.generateSamples(start: start, end: end);
if (samplePoints.First().value.dy.abs() > tolerance ||
(1.0f - samplePoints.Last().value.dy).abs() > tolerance)
{
bool bail = true;
success = false;
D.assert(() => {
reasons?.Add($"The curve has more than one Y value at X = {samplePoints.First().value.dx}. " +
"Try moving some control points further away from this value of X, or increasing " +
"the tension.");
bail = reasons == null;
return(true);
});
if (bail)
{
return(false);
}
}
foreach (Curve2DSample sample in samplePoints)
{
Offset point = sample.value;
float t = sample.t;
float x = point.dx;
if (t >= start && t <= end && (x < -1e-3f || x > 1.0f + 1e-3f))
{
bool bail = true;
success = false;
D.assert(() => {
reasons?.Add($"The resulting curve has an X value ({x}) which is outside " +
"the range [0.0, 1.0], inclusive.");
bail = reasons == null;
return(true);
});
if (bail)
{
return(false);
}
}
if (x < lastX)
{
bool bail = true;
success = false;
D.assert(() => {
reasons?.Add($"The curve has more than one Y value at x = {x}. Try moving " +
"some control points further apart in X, or increasing the tension.");
bail = reasons == null;
return(true);
});
if (bail)
{
return(false);
}
}
lastX = x;
}
return(success);
}