Add d3.pathFixed. Fixes #10.

Author: mbostock

index.js

@@ -1 +1 @@
-export {default as path} from "./src/path";
+export {default as path, pathFixed} from "./src/path";

src/path.js

@@ -15,8 +15,11 @@ function path() {
 
 Path.prototype = path.prototype = {
   constructor: Path,
+  _format: function(x) {
+    return x;
+  },
   moveTo: function(x, y) {
-    this._ += "M" + (this._x0 = this._x1 = +x) + "," + (this._y0 = this._y1 = +y);
+    this._ += "M" + this._format(this._x0 = this._x1 = +x) + "," + this._format(this._y0 = this._y1 = +y);
   },
   closePath: function() {
     if (this._x1 !== null) {
@@ -25,13 +28,13 @@ Path.prototype = path.prototype = {
     }
   },
   lineTo: function(x, y) {
-    this._ += "L" + (this._x1 = +x) + "," + (this._y1 = +y);
+    this._ += "L" + this._format(this._x1 = +x) + "," + this._format(this._y1 = +y);
   },
   quadraticCurveTo: function(x1, y1, x, y) {
-    this._ += "Q" + (+x1) + "," + (+y1) + "," + (this._x1 = +x) + "," + (this._y1 = +y);
+    this._ += "Q" + this._format(+x1) + "," + this._format(+y1) + "," + this._format(this._x1 = +x) + "," + this._format(this._y1 = +y);
   },
   bezierCurveTo: function(x1, y1, x2, y2, x, y) {
-    this._ += "C" + (+x1) + "," + (+y1) + "," + (+x2) + "," + (+y2) + "," + (this._x1 = +x) + "," + (this._y1 = +y);
+    this._ += "C" + this._format(+x1) + "," + this._format(+y1) + "," + this._format(+x2) + "," + this._format(+y2) + "," + this._format(this._x1 = +x) + "," + this._format(this._y1 = +y);
   },
   arcTo: function(x1, y1, x2, y2, r) {
     x1 = +x1, y1 = +y1, x2 = +x2, y2 = +y2, r = +r;
@@ -48,7 +51,7 @@ Path.prototype = path.prototype = {
 
     // Is this path empty? Move to (x1,y1).
     if (this._x1 === null) {
-      this._ += "M" + (this._x1 = x1) + "," + (this._y1 = y1);
+      this._ += "M" + this._format(this._x1 = x1) + "," + this._format(this._y1 = y1);
     }
 
     // Or, is (x1,y1) coincident with (x0,y0)? Do nothing.
@@ -58,7 +61,7 @@ Path.prototype = path.prototype = {
     // Equivalently, is (x1,y1) coincident with (x2,y2)?
     // Or, is the radius zero? Line to (x1,y1).
     else if (!(Math.abs(y01 * x21 - y21 * x01) > epsilon) || !r) {
-      this._ += "L" + (this._x1 = x1) + "," + (this._y1 = y1);
+      this._ += "L" + this._format(this._x1 = x1) + "," + this._format(this._y1 = y1);
     }
 
     // Otherwise, draw an arc!
@@ -75,10 +78,10 @@ Path.prototype = path.prototype = {
 
       // If the start tangent is not coincident with (x0,y0), line to.
       if (Math.abs(t01 - 1) > epsilon) {
-        this._ += "L" + (x1 + t01 * x01) + "," + (y1 + t01 * y01);
+        this._ += "L" + this._format(x1 + t01 * x01) + "," + this._format(y1 + t01 * y01);
       }
 
-      this._ += "A" + r + "," + r + ",0,0," + (+(y01 * x20 > x01 * y20)) + "," + (this._x1 = x1 + t21 * x21) + "," + (this._y1 = y1 + t21 * y21);
+      this._ += "A" + this._format(r) + "," + this._format(r) + ",0,0," + (+(y01 * x20 > x01 * y20)) + "," + this._format(this._x1 = x1 + t21 * x21) + "," + this._format(this._y1 = y1 + t21 * y21);
     }
   },
   arc: function(x, y, r, a0, a1, ccw) {
@@ -95,34 +98,41 @@ Path.prototype = path.prototype = {
 
     // Is this path empty? Move to (x0,y0).
     if (this._x1 === null) {
-      this._ += "M" + x0 + "," + y0;
+      this._ += "M" + this._format(x0) + "," + this._format(y0);
     }
 
     // Or, is (x0,y0) not coincident with the previous point? Line to (x0,y0).
     else if (Math.abs(this._x1 - x0) > epsilon || Math.abs(this._y1 - y0) > epsilon) {
-      this._ += "L" + x0 + "," + y0;
+      this._ += "L" + this._format(x0) + "," + this._format(y0);
     }
 
     // Is this arc empty? We’re done.
     if (!r) return;
 
     // Is this a complete circle? Draw two arcs to complete the circle.
     if (da > tauEpsilon) {
-      this._ += "A" + r + "," + r + ",0,1," + cw + "," + (x - dx) + "," + (y - dy) + "A" + r + "," + r + ",0,1," + cw + "," + (this._x1 = x0) + "," + (this._y1 = y0);
+      this._ += "A" + this._format(r) + "," + this._format(r) + ",0,1," + cw + "," + this._format(x - dx) + "," + this._format(y - dy) + "A" + this._format(r) + "," + this._format(r) + ",0,1," + cw + "," + this._format(this._x1 = x0) + "," + this._format(this._y1 = y0);
     }
 
     // Otherwise, draw an arc!
     else {
       if (da < 0) da = da % tau + tau;
-      this._ += "A" + r + "," + r + ",0," + (+(da >= pi)) + "," + cw + "," + (this._x1 = x + r * Math.cos(a1)) + "," + (this._y1 = y + r * Math.sin(a1));
+      this._ += "A" + this._format(r) + "," + this._format(r) + ",0," + (+(da >= pi)) + "," + cw + "," + this._format(this._x1 = x + r * Math.cos(a1)) + "," + this._format(this._y1 = y + r * Math.sin(a1));
     }
   },
   rect: function(x, y, w, h) {
-    this._ += "M" + (this._x0 = this._x1 = +x) + "," + (this._y0 = this._y1 = +y) + "h" + (+w) + "v" + (+h) + "h" + (-w) + "Z";
+    this._ += "M" + this._format(this._x0 = this._x1 = +x) + "," + this._format(this._y0 = this._y1 = +y) + "h" + this._format(+w) + "v" + this._format(+h) + "h" + this._format(-w) + "Z";
   },
   toString: function() {
     return this._;
   }
 };
 
 export default path;
+
+export function pathFixed(digits) {
+  var path = new Path;
+  (digits = +digits).toFixed(digits); // Validate digits.
+  path._format = function(x) { return +x.toFixed(digits); };
+  return path;
+}

test/pathFixed-test.js

@@ -0,0 +1,17 @@
+var tape = require("tape"),
+    path = require("../");
+
+tape("pathFixed.moveTo(x, y) limits the precision of x and y", function(test) {
+  var p = path.pathFixed(1);
+  p.moveTo(123.456, 789.012);
+  test.strictEqual(p + "", "M123.5,789");
+  test.end();
+});
+
+tape("pathFixed.lineTo(x, y) limits the precision of x and y", function(test) {
+  var p = path.pathFixed(1);
+  p.moveTo(0, 0);
+  p.lineTo(123.456, 789.012);
+  test.strictEqual(p + "", "M0,0L123.5,789");
+  test.end();
+});