Various changes to #isCollinear(), #isOrthogonal(), #isArc()

- Rename #isArc() - > #isOrthogonalArc()
- Implement versions for Curve
- Write proper documentation

src/path/Curve.js

@@ -314,6 +314,29 @@ var Curve = Base.extend(/** @lends Curve# */{
         return this._segment1.isLinear();
     },
 
+    /**
+     * Checks if the the two curves describe lines that are collinear, meaning
+     * they run in parallel.
+     *
+     * @param {Curve} the other curve to check against
+     * @return {Boolean} {@true if the two lines are collinear}
+     * @see Segment#isCollinear(segment)
+     */
+    isCollinear: function(curve) {
+        return this._segment1.isCollinear(curve._segment1);
+    },
+
+    /**
+     * Checks if the curve describes an orthogonal arc, as used in the
+     * construction of circles and ellipses.
+     *
+     * @return {Boolean} {@true if the curve describes an orthogonal arc}
+     * @see Segment#isOrthogonalArc()
+     */
+    isOrthogonalArc: function() {
+        return this._segment1.isOrthogonalArc();
+    },
+
     // DOCS: Curve#getIntersections()
     getIntersections: function(curve) {
         return Curve.filterIntersections(Curve.getIntersections(

src/path/Path.js

@@ -1418,7 +1418,7 @@ var Path = PathItem.extend(/** @lends Path# */{
         }
 
         function isArc(i) {
-            return segments[i].isArc();
+            return segments[i].isOrthogonalArc();
         }
 
         function getDistance(i, j) {

src/path/Segment.js

@@ -268,8 +268,12 @@ var Segment = Base.extend(/** @lends Segment# */{
     },
 
     /**
-     * Returns true if the the two segments are the beginning of two lines and
+     * Checks if the the two segments are the beginning of two lines that are
-     * if these two lines are running parallel.
+     * collinear, meaning they run in parallel.
+     *
+     * @param {Segment} the other segment to check against
+     * @return {Boolean} {@true if the two lines are collinear}
+     * @see Curve#isCollinear(curve)
      */
     isCollinear: function(segment) {
         var next1 = this.getNext(),
@@ -283,6 +287,13 @@ var Segment = Base.extend(/** @lends Segment# */{
     // TODO: Remove version with typo after a while (deprecated June 2015)
     isColinear: '#isCollinear',
 
+    /**
+     * Checks if the segment is connecting two lines that are orthogonal,
+     * meaning they connect at an 90° angle.
+     *
+     * @return {Boolean} {@true if the two lines connected by this segment are
+     * orthogonal}
+     */
     isOrthogonal: function() {
         var prev = this.getPrevious(),
             next = this.getNext();
@@ -293,16 +304,20 @@ var Segment = Base.extend(/** @lends Segment# */{
     },
 
     /**
-     * Returns true if the segment at the given index is the beginning of an
+     * Checks if the segment is the beginning of an orthogonal arc, as used in
-     * orthogonal arc segment. The code looks at the length of the handles and
+     * the construction of circles and ellipses.
-     * their relation to the distance to the imaginary corner point. If the
+     *
-     * relation is kappa, then it's an arc.
+     * @return {Boolean} {@true if the segment is the beginning of an orthogonal
+     * arc}
+     * @see Curve#isOrthogonalArc()
      */
-    isArc: function() {
+    isOrthogonalArc: function() {
         var next = this.getNext(),
             handle1 = this._handleOut,
             handle2 = next._handleIn,
             kappa = /*#=*/Numerical.KAPPA;
+        // Look at the length of the handles and their relation to the distance
+        // to the imaginary corner point and see if it their relation is kappa.
         if (handle1.isOrthogonal(handle2)) {
             var from = this._point,
                 to = next._point,
@@ -318,6 +333,9 @@ var Segment = Base.extend(/** @lends Segment# */{
         return false;
     },
 
+    // TODO: Remove a while (deprecated August 2015)
+    isArc: '#isOrthogonalArc',
+
     _selectionState: 0,
 
     /**