// This function is nearly identical to the one written for the
// original port of the F3 graphics/UI library:
// javafx.ui.canvas.ArcTo#addTo
private void addArcTo(NGPath pgPath, Path2D path, final double x0, final double y0) {
double localX = getX();
double localY = getY();
boolean localSweepFlag = isSweepFlag();
boolean localLargeArcFlag = isLargeArcFlag();
// Determine target "to" position
final double xto = (isAbsolute()) ? localX : localX + x0;
final double yto = (isAbsolute()) ? localY : localY + y0;
// Compute the half distance between the current and the final point
final double dx2 = (x0 - xto) / 2.0;
final double dy2 = (y0 - yto) / 2.0;
// Convert angle from degrees to radians
final double xAxisRotationR = Math.toRadians(getXAxisRotation());
final double cosAngle = Math.cos(xAxisRotationR);
final double sinAngle = Math.sin(xAxisRotationR);
//
// Step 1 : Compute (x1, y1)
//
final double x1 = (cosAngle * dx2 + sinAngle * dy2);
final double y1 = (-sinAngle * dx2 + cosAngle * dy2);
// Ensure radii are large enough
double rx = Math.abs(getRadiusX());
double ry = Math.abs(getRadiusY());
double Prx = rx * rx;
double Pry = ry * ry;
final double Px1 = x1 * x1;
final double Py1 = y1 * y1;
// check that radii are large enough
final double radiiCheck = Px1 / Prx + Py1 / Pry;
if (radiiCheck > 1.0) {
rx = Math.sqrt(radiiCheck) * rx;
ry = Math.sqrt(radiiCheck) * ry;
if (rx == rx && ry == ry) {
/* not NANs */
} else {
if (pgPath == null) {
path.lineTo((float) xto, (float) yto);
} else {
pgPath.addLineTo((float) xto, (float) yto);
}
return;
}
Prx = rx * rx;
Pry = ry * ry;
}
//
// Step 2 : Compute (cx1, cy1)
//
double sign = ((localLargeArcFlag == localSweepFlag) ? -1.0 : 1.0);
double sq = ((Prx * Pry) - (Prx * Py1) - (Pry * Px1)) / ((Prx * Py1) + (Pry * Px1));
sq = (sq < 0.0) ? 0.0 : sq;
final double coef = (sign * Math.sqrt(sq));
final double cx1 = coef * ((rx * y1) / ry);
final double cy1 = coef * -((ry * x1) / rx);
//
// Step 3 : Compute (cx, cy) from (cx1, cy1)
//
final double sx2 = (x0 + xto) / 2.0;
final double sy2 = (y0 + yto) / 2.0;
final double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
final double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);
//
// Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
//
final double ux = (x1 - cx1) / rx;
final double uy = (y1 - cy1) / ry;
final double vx = (-x1 - cx1) / rx;
final double vy = (-y1 - cy1) / ry;
// Compute the angle start
double n = Math.sqrt((ux * ux) + (uy * uy));
double p = ux; // (1 * ux) + (0 * uy)
sign = ((uy < 0.0) ? -1.0 : 1.0);
double angleStart = Math.toDegrees(sign * Math.acos(p / n));
// Compute the angle extent
n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
p = ux * vx + uy * vy;
sign = ((ux * vy - uy * vx < 0.0) ? -1.0 : 1.0);
double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
if (!localSweepFlag && (angleExtent > 0)) {
angleExtent -= 360.0;
} else if (localSweepFlag && (angleExtent < 0)) {
angleExtent += 360.0;
}
angleExtent = angleExtent % 360;
angleStart = angleStart % 360;
//
// We can now build the resulting Arc2D
//
final float arcX = (float) (cx - rx);
final float arcY = (float) (cy - ry);
final float arcW = (float) (rx * 2.0);
final float arcH = (float) (ry * 2.0);
final float arcStart = (float) -angleStart;
final float arcExtent = (float) -angleExtent;
if (pgPath == null) {
final Arc2D arc = new Arc2D(arcX, arcY, arcW, arcH, arcStart, arcExtent, Arc2D.OPEN);
BaseTransform xform =
(xAxisRotationR == 0) ? null : BaseTransform.getRotateInstance(xAxisRotationR, cx, cy);
PathIterator pi = arc.getPathIterator(xform);
// RT-8926, append(true) converts the initial moveTo into a
// lineTo which can generate huge miter joins if the segment
// is small enough. So, we manually skip it here instead.
pi.next();
path.append(pi, true);
} else {
pgPath.addArcTo(arcX, arcY, arcW, arcH, arcStart, arcExtent, (float) xAxisRotationR);
}
}
@Override
void addTo(NGPath pgPath) {
addArcTo(pgPath, null, pgPath.getCurrentX(), pgPath.getCurrentY());
}