scratchfoundation/paper.js
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Simplify and clean-up PathItem._getWinding() code.

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This commit is contained in:
Jürg Lehni 2014-02-20 00:19:44 +01:00
parent 6af639946b
commit 36394c4c56
1 changed files with 36 additions and 60 deletions
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96
src/path/PathItem.js
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@ -359,24 +359,7 @@ var PathItem = Item.extend(/** @lends PathItem# */{
* given point with respect to a given set of monotone curves.
*/
_getWinding: function _getWinding(point, curves, horizontal) {
function getTangent(v, t) {
var sign = t === 0 ? 2 : t === 1 ? -2 : 0,
tan;
if (sign !== 0) {
// Return slope from this point that follows the direction
// of the line
if (Curve.isLinear(v))
sign *= 3;
var i = sign > 0 ? 0 : 6;
tan = new Point(v[i + sign] - v[i], v[i + sign + 1] - v[i + 1]);
} else {
tan = Curve.evaluate(v, t, 1);
}
return tan;
}
var i, j, li, t, x0, y0, wind, v, slope, stationary,
tolerance = /*#=*/ Numerical.TOLERANCE,
var tolerance = /*#=*/ Numerical.TOLERANCE,
x = point.x,
y = point.y,
xAfter = x + tolerance,
@ -390,17 +373,17 @@ var PathItem = Item.extend(/** @lends PathItem# */{
// indeterminate state.
if (horizontal) {
var yTop = -Infinity,
yBot = Infinity;
// Find the closest yIntercepts in the same vertical line
for (i = 0, li = curves.length-1; i <= li; i++) {
yBottom = Infinity;
// Find the closest top and bottom intercepts for the same vertical
// line.
for (var i = 0, l = curves.length; i < l; i++) {
v = curves[i];
if (Curve.solveCubic(v, 0, x, roots, 0, 1) > 0) {
for (j = roots.length - 1; j >= 0; j--) {
t = roots[j];
y0 = Curve.evaluate(v, t, 0).y;
if (y0 > y+tolerance && y0 < yBot) {
yBot = y0;
} else if (y0 < y-tolerance && y0 > yTop) {
for (var j = roots.length - 1; j >= 0; j--) {
var y0 = Curve.evaluate(v, roots[j], 0).y;
if (y0 > y + tolerance && y0 < yBottom) {
yBottom = y0;
} else if (y0 < y - tolerance && y0 > yTop) {
yTop = y0;
}
}
@ -409,44 +392,37 @@ var PathItem = Item.extend(/** @lends PathItem# */{
// Shift the point lying on the horizontal curves by
// half of closest top and bottom intercepts.
yTop = (yTop + y) / 2;
yBot = (yBot + y) / 2;
windLeft = yTop > -Infinity
? _getWinding(new Point(x, yTop), curves)
: 0;
windRight = yBot < Infinity
? _getWinding(new Point(x, yBot), curves)
: 0;
yBottom = (yBottom + y) / 2;
if (yTop > -Infinity)
windLeft = _getWinding(new Point(x, yTop), curves);
if (yBottom < Infinity)
windRight = _getWinding(new Point(x, yBottom), curves);
return Math.max(windLeft, windRight);
}
// Find the winding number for right hand side of the curve,
// inclusive of the curve itself, while tracing along its ±x direction.
for (i = 0, li = curves.length-1; i <= li; i++) {
v = curves[i];
if (Curve.solveCubic(v, 1, y, roots, -tolerance, 1 + -tolerance) === 1) {
t = roots[0];
if ( t >= -tolerance && t <= tolerance)
t = 0;
x0 = Curve.evaluate(v, t, 0).x;
slope = getTangent(v, t).y;
stationary = !Curve.isLinear(v) && abs(slope) < tolerance;
// Take care of cases where the curve and the preceeding
// curve merely touches the ray towards ±x direction, but
// proceeds to the same side of the ray. This essentially is
// not a crossing.
if (t === 0) {
// The previous curve's reference is stored at index:9,
// see Path#_getMonotoneCurves for details.
var v2 = v[9];
if (abs(v2[6] - v[0]) < tolerance
&& abs(v2[7] - v[1]) < tolerance
&& slope * getTangent(v2, 1).y > 0)
stationary = true;
for (var i = 0, l = curves.length; i < l; i++) {
var v = curves[i];
if (Curve.solveCubic(v, 1, y, roots, 0, 1 - tolerance) === 1) {
var t = roots[0],
x0 = Curve.evaluate(v, t, 0).x,
slope = Curve.evaluate(v, t, 1).y,
stationary = abs(slope) < tolerance && !Curve.isLinear(v)
// Take care of cases where the curve and the
// preceeding curve merely touches the ray towards
// +-x direction, but proceeds to the same side of
// the ray. This essentially is not a crossing.
// NOTE: The previous curve is stored at v[9],
// see Path#_getMonotoneCurves() for details.
|| t < tolerance
&& slope * Curve.evaluate(v[9], t, 1).y < 0;
if (!stationary) {
var winding = v[8];
if (x0 <= xBefore)
windLeft += winding;
if (x0 >= xAfter)
windRight += winding;
}
wind = v[8];
if (x0 <= xBefore && !stationary)
windLeft += wind;
if (x0 >= xAfter && !stationary)
windRight += wind;
}
}
return Math.max(abs(windLeft), abs(windRight));