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Small improvement in Path#arcTo() to reduce segment account in edge cases.

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This commit is contained in:
Jürg Lehni 2017-02-22 13:57:51 +01:00
parent d204175d39
commit ba2b18c7dc
1 changed files with 12 additions and 8 deletions
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20
src/path/Path.js
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@ -2402,7 +2402,9 @@ new function() { // PostScript-style drawing commands
arcTo: function(/* to, clockwise | through, to
| to, radius, rotation, clockwise, large */) {
// Get the start point:
var current = getCurrentSegment(this),
var abs = Math.abs,
sqrt = Math.sqrt,
current = getCurrentSegment(this),
from = current._point,
to = Point.read(arguments),
through,
@ -2441,7 +2443,6 @@ new function() { // PostScript-style drawing commands
pt = from.subtract(middle).rotate(-rotation),
x = pt.x,
y = pt.y,
abs = Math.abs,
rx = abs(radius.width),
ry = abs(radius.height),
rxSq = rx * rx,
@ -2449,7 +2450,7 @@ new function() { // PostScript-style drawing commands
xSq = x * x,
ySq = y * y;
// "...ensure radii are large enough"
var factor = Math.sqrt(xSq / rxSq + ySq / rySq);
var factor = sqrt(xSq / rxSq + ySq / rySq);
if (factor > 1) {
rx *= factor;
ry *= factor;
@ -2466,8 +2467,7 @@ new function() { // PostScript-style drawing commands
center = new Point(rx * y / ry, -ry * x / rx)
// "...where the + sign is chosen if fA != fS,
// and the - sign is chosen if fA = fS."
.multiply((large === clockwise ? -1 : 1)
* Math.sqrt(factor))
.multiply((large === clockwise ? -1 : 1) * sqrt(factor))
.rotate(rotation).add(middle);
// Now create a matrix that maps the unit circle to the ellipse,
// for easier construction below.
@ -2514,7 +2514,7 @@ new function() { // PostScript-style drawing commands
// If the center is lying on the line, we might have gotten
// the wrong sign for extent above. Use the sign of the side
// of the through point.
extent = throughSide * Math.abs(extent);
extent = throughSide * abs(extent);
} else if (throughSide === centerSide) {
// If the center is on the same side of the line (from, to)
// as the through point, we're extending bellow 180 degrees
@ -2522,8 +2522,12 @@ new function() { // PostScript-style drawing commands
extent += extent < 0 ? 360 : -360;
}
}
var ext = Math.abs(extent),
count = ext >= 360 ? 4 : Math.ceil(ext / 90),
var epsilon = /*#=*/Numerical.EPSILON,
ext = abs(extent),
// Calculate the amount of segments required to approximate over
// `extend` degrees (extend / 90), but prevent ceil() from
// rounding up small imprecisions by subtracting epsilon first.
count = ext >= 360 ? 4 : Math.ceil((ext - epsilon) / 90),
inc = extent / count,
half = inc * Math.PI / 360,
z = 4 / 3 * Math.sin(half) / (1 + Math.cos(half)),