scratchfoundation/paper.js
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Handle special case of infinitely big circle in Path#arcTo(), by cheating using an approximation of a really big circle.

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This commit is contained in:
Jürg Lehni 2011-06-14 12:45:37 +01:00
parent 5a601f39a4
commit 50bc64779f
1 changed files with 15 additions and 6 deletions
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21
src/path/Path.js
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@ -1758,7 +1758,6 @@ var Path = this.Path = PathItem.extend({
step = middle.subtract(from); step = middle.subtract(from);
through = middle[clockwise ? 'subtract' : 'add'](-step.y, step.x); through = middle[clockwise ? 'subtract' : 'add'](-step.y, step.x);
} }
// Construct the two perpendicular middle lines to (from, through) // Construct the two perpendicular middle lines to (from, through)
// and (through, to), and intersect them to get the center // and (through, to), and intersect them to get the center
var l1 = new Line(from.add(through).divide(2), var l1 = new Line(from.add(through).divide(2),
@ -1766,14 +1765,24 @@ var Path = this.Path = PathItem.extend({
l2 = new Line(through.add(to).divide(2), l2 = new Line(through.add(to).divide(2),
to.subtract(through).rotate(90)), to.subtract(through).rotate(90)),
center = l1.intersect(l2), center = l1.intersect(l2),
vector = from.subtract(center), line = new Line(from, to, true),
side = line.getSide(through);
if (!center) {
// If the two lines are colinear, there cannot be an arc as the
// circle is infinitely big and has no center point.
// We're cheating by producing a center point that's just really
// far away. While this is wrong, it graphically produces the
// expected results...
center = from.add(to).divide(2).add(to.subtract(from).rotate(
-90 * (side || 1)).multiply(10e9));
}
var vector = from.subtract(center),
radius = vector.getLength(), radius = vector.getLength(),
extent = vector.getDirectedAngle(to.subtract(center)), extent = vector.getDirectedAngle(to.subtract(center));
line = new Line(from, to, true); // If the center is on the same side of the line (from, to) as
// If the center is on the same side of the line (from, to) than
// the through point, we're extending bellow 180 degrees and need // the through point, we're extending bellow 180 degrees and need
// to adapt extent. // to adapt extent.
if (line.getSide(center) == line.getSide(through)) if (side == line.getSide(center))
extent -= 360 * (extent < 0 ? -1 : 1); extent -= 360 * (extent < 0 ? -1 : 1);
var ext = Math.abs(extent), var ext = Math.abs(extent),
count = ext >= 360 ? 4 : Math.ceil(ext / 90), count = ext >= 360 ? 4 : Math.ceil(ext / 90),