fix(modeling): handle label layouting edge case

Related to #669

lib/features/modeling/behavior/util/LabelLayoutUtil.js

@@ -112,7 +112,7 @@ function getLabelAdjustment(label, newWaypoints, oldWaypoints, hints) {
       oldLabelLineIndex = attachment.segmentIndex,
       newLabelLineIndex = findNewLabelLineStartIndex(oldWaypoints, newWaypoints, attachment, hints);
 
-  if ( newLabelLineIndex === null ) {
+  if (newLabelLineIndex === null) {
     return { x: x, y: y };
   }
 
@@ -210,8 +210,9 @@ function getLine(waypoints, idx) {
 }
 
 function getRelativeFootPosition(line, foot) {
+
   var length = getDistancePointPoint(line[0], line[1]),
       lengthToFoot = getDistancePointPoint(line[0], foot);
 
-  return lengthToFoot / length;
+  return length === 0 ? 0 : lengthToFoot / length;
 }

lib/features/modeling/behavior/util/LineAttachmentUtil.js

@@ -151,10 +151,12 @@ function getCircleSegmentIntersections(s1, s2, cc, cr) {
 
   var disc = pBy2 * pBy2 - q;
 
-  // round disc to 10 digits to work around
+  // check against negative value to work around
   // negative, very close to zero results (-4e-15)
   // being produced in some environments
-  disc = round(disc, 10);
+  if (disc < 0 && disc > -0.000001) {
+    disc = 0;
+  }
 
   if (disc < 0) {
     return [];
@@ -220,26 +222,6 @@ function mid(p1, p2) {
   };
 }
 
-/**
- * Round number to precision
- *
- * @param {Number} number
- * @param {Integer} [precision=1]
- *
- * @return {Number}
- */
-function round(number, precision) {
-
-  if (typeof precision === 'undefined') {
-    return Math.round(number);
-  }
-
-  var factor = Math.pow(10, precision);
-  var tempNumber = number * factor;
-  var roundedTempNumber = Math.round(tempNumber);
-  return roundedTempNumber / factor;
-}
-
 var EQUAL_THRESHOLD = 0.1;
 
 function pointsEqual(p1, p2) {

test/spec/features/modeling/behavior/util/LabelLayoutUtilSpec.js

@@ -0,0 +1,75 @@
+'use strict';
+
+var getLabelAdjustment = require('lib/features/modeling/behavior/util/LabelLayoutUtil').getLabelAdjustment;
+
+
+describe('modeling/behavior/util - LabelLayoutUtil#getLabelAdjustment', function() {
+
+  describe('should recognize on the line label', function() {
+
+    var newLine = [
+      { x: 10, y: 10 },
+      // -
+      { x: 15, y: 10 },
+      // |
+      { x: 15, y: 5 },
+      // -
+      { x: 30, y: 5 }
+    ];
+
+
+    it('horizontal', function() {
+
+      // given
+      var line = [
+        { x: 10, y: 10 },
+        // -
+        { x: 20, y: 10 }
+      ];
+
+      // label with center { x: 5, y: 10 }
+
+      var label = {
+        x: 0,
+        y: 5,
+        width: 10,
+        height: 10
+      };
+
+      // when
+      var delta = getLabelAdjustment(label, newLine, line, { connectionStart: true });
+
+      // then
+      expect(delta).to.eql({ x: 0, y: 0 });
+    });
+
+
+    it('zero-length line', function() {
+
+      // given
+      var line = [
+        { x: 10, y: 10 },
+        // -
+        { x: 10, y: 10 }
+      ];
+
+      // label with center { x: 5, y: 10 }
+
+      var label = {
+        x: 0,
+        y: 5,
+        width: 10,
+        height: 10
+      };
+
+      // when
+      var delta = getLabelAdjustment(label, newLine, line, { connectionStart: true });
+
+      // then
+      expect(delta).to.eql({ x: 0, y: 0 });
+    });
+
+  });
+
+
+});