Remove caching of some path parsing steps (fabricjs#5140)

* disable caching

* missing jsdocs

* missing jsdocs

* added jsdocs

HEADER.js

@@ -140,6 +140,28 @@ fabric.devicePixelRatio = fabric.window.devicePixelRatio ||
  */
 fabric.browserShadowBlurConstant = 1;
 
+/**
+ * This object contains the result of arc to beizer conversion for faster retrieving if the same arc needs to be converted again.
+ * It was an internal variable, is accessible since version 2.3.4
+ */
+fabric.arcToSegmentsCache = { };
+
+/**
+ * This object keeps the results of the boundsOfCurve calculation mapped by the joined arguments necessary to calculate it.
+ * It does speed up calculation, if you parse and add always the same paths, but in case of heavy usage of freedrawing
+ * you do not get any speed benefit and you get a big object in memory.
+ * The object was a private variable before, while now is appended to the lib so that you have access to it and you
+ * can eventually clear it.
+ * It was an internal variable, is accessible since version 2.3.4
+ */
+fabric.boundsOfCurveCache = { };
+
+/**
+ * If disabled boundsOfCurveCache is not used. For apps that make heavy usage of pencil drawing probably disabling it is better
+ * @default true
+ */
+fabric.cachesBoundsOfCurve = true;
+
 fabric.initFilterBackend = function() {
   if (fabric.enableGLFiltering && fabric.isWebglSupported && fabric.isWebglSupported(fabric.textureSize)) {
     console.log('max texture size: ' + fabric.maxTextureSize);

src/util/arc.js

@@ -1,18 +1,15 @@
 (function() {
 
-  var arcToSegmentsCache = { },
-      segmentToBezierCache = { },
-      boundsOfCurveCache = { },
-      _join = Array.prototype.join;
+  var _join = Array.prototype.join;
 
   /* Adapted from http://dxr.mozilla.org/mozilla-central/source/content/svg/content/src/nsSVGPathDataParser.cpp
    * by Andrea Bogazzi code is under MPL. if you don't have a copy of the license you can take it here
    * http://mozilla.org/MPL/2.0/
    */
   function arcToSegments(toX, toY, rx, ry, large, sweep, rotateX) {
     var argsString = _join.call(arguments);
-    if (arcToSegmentsCache[argsString]) {
-      return arcToSegmentsCache[argsString];
+    if (fabric.arcToSegmentsCache[argsString]) {
+      return fabric.arcToSegmentsCache[argsString];
     }
 
     var PI = Math.PI, th = rotateX * PI / 180,
@@ -66,16 +63,11 @@
       mTheta = th3;
       th3 += mDelta;
     }
-    arcToSegmentsCache[argsString] = result;
+    fabric.arcToSegmentsCache[argsString] = result;
     return result;
   }
 
   function segmentToBezier(th2, th3, cosTh, sinTh, rx, ry, cx1, cy1, mT, fromX, fromY) {
-    var argsString2 = _join.call(arguments);
-    if (segmentToBezierCache[argsString2]) {
-      return segmentToBezierCache[argsString2];
-    }
-
     var costh2 = fabric.util.cos(th2),
         sinth2 = fabric.util.sin(th2),
         costh3 = fabric.util.cos(th3),
@@ -87,12 +79,11 @@
         cp2X = toX + mT * ( cosTh * rx * sinth3 + sinTh * ry * costh3),
         cp2Y = toY + mT * ( sinTh * rx * sinth3 - cosTh * ry * costh3);
 
-    segmentToBezierCache[argsString2] = [
+    return [
       cp1X, cp1Y,
       cp2X, cp2Y,
       toX, toY
     ];
-    return segmentToBezierCache[argsString2];
   }
 
   /*
@@ -178,9 +169,12 @@
    */
   // taken from http://jsbin.com/ivomiq/56/edit  no credits available for that.
   function getBoundsOfCurve(x0, y0, x1, y1, x2, y2, x3, y3) {
-    var argsString = _join.call(arguments);
-    if (boundsOfCurveCache[argsString]) {
-      return boundsOfCurveCache[argsString];
+    var argsString;
+    if (fabric.cachesBoundsOfCurve) {
+      argsString = _join.call(arguments);
+      if (fabric.boundsOfCurveCache[argsString]) {
+        return fabric.boundsOfCurveCache[argsString];
+      }
     }
 
     var sqrt = Math.sqrt,
@@ -250,7 +244,9 @@
         y: max.apply(null, bounds[1])
       }
     ];
-    boundsOfCurveCache[argsString] = result;
+    if (fabric.cachesBoundsOfCurve) {
+      fabric.boundsOfCurveCache[argsString] = result;
+    }
     return result;
   }