/// <summary>
/// Initializes a new instance of the <see cref="EllipseGeometry"/> class.
/// </summary>
/// <param name="rect">The rectangle that the ellipse should fill.</param>
public EllipseGeometry(Rect rect)
{
IPlatformRenderInterface factory = PerspexLocator.Current.GetService <IPlatformRenderInterface>();
IStreamGeometryImpl impl = factory.CreateStreamGeometry();
using (IStreamGeometryContextImpl ctx = impl.Open())
{
double controlPointRatio = (Math.Sqrt(2) - 1) * 4 / 3;
var center = rect.Center;
var radius = new Vector(rect.Width / 2, rect.Height / 2);
var x0 = center.X - radius.X;
var x1 = center.X - (radius.X * controlPointRatio);
var x2 = center.X;
var x3 = center.X + (radius.X * controlPointRatio);
var x4 = center.X + radius.X;
var y0 = center.Y - radius.Y;
var y1 = center.Y - (radius.Y * controlPointRatio);
var y2 = center.Y;
var y3 = center.Y + (radius.Y * controlPointRatio);
var y4 = center.Y + radius.Y;
ctx.BeginFigure(new Point(x2, y0), true);
ctx.BezierTo(new Point(x3, y0), new Point(x4, y1), new Point(x4, y2));
ctx.BezierTo(new Point(x4, y3), new Point(x3, y4), new Point(x2, y4));
ctx.BezierTo(new Point(x1, y4), new Point(x0, y3), new Point(x0, y2));
ctx.BezierTo(new Point(x0, y1), new Point(x1, y0), new Point(x2, y0));
ctx.EndFigure(true);
}
PlatformImpl = impl;
}
public static void QuadTo(IStreamGeometryContextImpl context, Point current, Point controlPoint, Point endPoint)
{
//(s, (s + 2c)/ 3, (e + 2c)/ 3, e)
context.BezierTo((current + 2*controlPoint)/3, (endPoint + 2*controlPoint)/3, endPoint);
}
/// <summary>
/// Draws a Bezier curve to the specified point.
/// </summary>
/// <param name="point1">The first control point used to specify the shape of the curve.</param>
/// <param name="point2">The second control point used to specify the shape of the curve.</param>
/// <param name="point3">The destination point for the end of the curve.</param>
public void BezierTo(Point point1, Point point2, Point point3)
{
_impl.BezierTo(point1, point2, point3);
}
/// <summary>
/// Builds the arc outline using given StreamGeometryContext
/// </summary>
/// <param name="path">A StreamGeometryContext to output the path commands to</param>
/// <param name="degree">degree of the Bezier curve to use</param>
/// <param name="threshold">acceptable error</param>
/// <param name="openNewFigure">if true, a new figure will be started in the specified StreamGeometryContext</param>
public void BuildArc(IStreamGeometryContextImpl path, int degree, double threshold, bool openNewFigure)
{
if (degree < 1 || degree > _maxDegree)
throw new ArgumentException($"degree should be between {1} and {_maxDegree}", nameof(degree));
// find the number of Bezier curves needed
bool found = false;
int n = 1;
double dEta;
double etaB;
while (!found && n < 1024)
{
dEta = (Eta2 - Eta1) / n;
if (dEta <= 0.5 * Math.PI)
{
etaB = Eta1;
found = true;
for (int i = 0; found && i < n; ++i)
{
double etaA = etaB;
etaB += dEta;
found = EstimateError(degree, etaA, etaB) <= threshold;
}
}
n = n << 1;
}
dEta = (Eta2 - Eta1) / n;
etaB = Eta1;
double cosEtaB = Math.Cos(etaB);
double sinEtaB = Math.Sin(etaB);
double aCosEtaB = A * cosEtaB;
double bSinEtaB = B * sinEtaB;
double aSinEtaB = A * sinEtaB;
double bCosEtaB = B * cosEtaB;
double xB = Cx + aCosEtaB * _cosTheta - bSinEtaB * _sinTheta;
double yB = Cy + aCosEtaB * _sinTheta + bSinEtaB * _cosTheta;
double xBDot = -aSinEtaB * _cosTheta - bCosEtaB * _sinTheta;
double yBDot = -aSinEtaB * _sinTheta + bCosEtaB * _cosTheta;
/*
This controls the drawing in case of pies
if (openNewFigure)
{
if (IsPieSlice)
{
path.BeginFigure(new Point(Cx, Cy), false, false);
path.LineTo(new Point(xB, yB), true, true);
}
else
{
path.BeginFigure(new Point(xB, yB), false, false);
}
}
else
{
//path.LineTo(new Point(xB, yB), true, true);
}
*/
//otherwise we're supposed to be already at the (xB,yB)
double t = Math.Tan(0.5 * dEta);
double alpha = Math.Sin(dEta) * (Math.Sqrt(4 + 3 * t * t) - 1) / 3;
for (int i = 0; i < n; ++i)
{
//double etaA = etaB;
double xA = xB;
double yA = yB;
double xADot = xBDot;
double yADot = yBDot;
etaB += dEta;
cosEtaB = Math.Cos(etaB);
sinEtaB = Math.Sin(etaB);
aCosEtaB = A * cosEtaB;
bSinEtaB = B * sinEtaB;
aSinEtaB = A * sinEtaB;
bCosEtaB = B * cosEtaB;
xB = Cx + aCosEtaB * _cosTheta - bSinEtaB * _sinTheta;
yB = Cy + aCosEtaB * _sinTheta + bSinEtaB * _cosTheta;
xBDot = -aSinEtaB * _cosTheta - bCosEtaB * _sinTheta;
yBDot = -aSinEtaB * _sinTheta + bCosEtaB * _cosTheta;
if (degree == 1)
{
path.LineTo(new Point(xB, yB));
}
else if (degree == 2)
{
double k = (yBDot * (xB - xA) - xBDot * (yB - yA)) / (xADot * yBDot - yADot * xBDot);
path.QuadTo(new Point(xA + k * xADot, yA + k * yADot), new Point(xB, yB));
}
else
{
path.BezierTo(
new Point(xA + alpha * xADot, yA + alpha * yADot),
new Point(xB - alpha * xBDot, yB - alpha * yBDot),
new Point(xB, yB)
);
}
}
if (IsPieSlice)
{
path.LineTo(new Point(Cx, Cy));
}
}
public static void QuadTo(IStreamGeometryContextImpl context, Point current, Point controlPoint, Point endPoint)
{
//(s, (s + 2c)/ 3, (e + 2c)/ 3, e)
context.BezierTo((current + 2 * controlPoint) / 3, (endPoint + 2 * controlPoint) / 3, endPoint);
}
