From 50bc64779fdffc67be284246c0797b8a90a02693 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=BCrg=20Lehni?= <juerg@scratchdisk.com>
Date: Tue, 14 Jun 2011 12:45:37 +0100
Subject: [PATCH] Handle special case of infinitely big circle in Path#arcTo(),
by cheating using an approximation of a really big circle.
---
src/path/Path.js | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/src/path/Path.js b/src/path/Path.js
index 22169a2e..6f4dbd24 100644
--- a/src/path/Path.js
+++ b/src/path/Path.js
@@ -1758,7 +1758,6 @@ var Path = this.Path = PathItem.extend({
step = middle.subtract(from);
through = middle[clockwise ? 'subtract' : 'add'](-step.y, step.x);
}
-
// Construct the two perpendicular middle lines to (from, through)
// and (through, to), and intersect them to get the center
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),
to.subtract(through).rotate(90)),
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(),
- 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) than
+ extent = vector.getDirectedAngle(to.subtract(center));
+ // If the center is on the same side of the line (from, to) as
// the through point, we're extending bellow 180 degrees and need
// to adapt extent.
- if (line.getSide(center) == line.getSide(through))
+ if (side == line.getSide(center))
extent -= 360 * (extent < 0 ? -1 : 1);
var ext = Math.abs(extent),
count = ext >= 360 ? 4 : Math.ceil(ext / 90),