fix(axis): Avoid unnecessary computing char dimension

Moved and updated condition on getSizeFor1Char() call to avoid multiple calls.

Ref #399
Close #407

package.json

@@ -67,6 +67,7 @@
     "eslint-config-naver": "^2.0.0",
     "eslint-loader": "^2.0.0",
     "eslint-plugin-import": "^2.11.0",
+    "exports-loader": "^0.7.0",
     "hammer-simulator": "0.0.1",
     "husky": "^0.14.3",
     "inject-loader": "^4.0.1",

spec/internals/axis-spec.js

@@ -6,6 +6,7 @@
 import util from "../assets/util";
 import bb from "../../src/core";
 import CLASS from "../../src/config/classes";
+import getSizeFor1Char from "exports-loader?getSizeFor1Char!../../src/axis/bb.axis";
 
 describe("AXIS", function() {
 	let chart;
@@ -82,6 +83,13 @@ describe("AXIS", function() {
 			args.axis.y.tick.values = values;
 		});
 
+		it("should compute char dimension", () => {
+			const size = getSizeFor1Char(d3.select(".tick"));
+
+			expect(size.w && size.h).to.be.ok;
+			expect(getSizeFor1Char.size).to.be.equal(size);
+		});
+
 		it("should have only 2 tick on y axis", () => {
 			const ticksSize = chart.internal.main.select(`.${CLASS.axisY}`)
 				.selectAll("g.tick").size();
@@ -1006,7 +1014,6 @@ describe("AXIS", function() {
 		});
 	});
 
-
 	describe("axis text on 'binary floating point'", () => {
 		before(() => {
 			args = {

src/axis/bb.axis.js

@@ -12,6 +12,37 @@ import {isArray, toArray, isDefined, isFunction, isString} from "../internals/ut
 // 2. ceil values of translate/x/y to int for half pixel anti-aliasing
 // 3. multiline tick text
 
+/**
+ * Compute a character dimension
+ * @param {d3.selection} node
+ * @return {{w: number, h: number}}
+ * @private
+ */
+const getSizeFor1Char = node => {
+	// default size for one character
+	const size = {
+		w: 5.5,
+		h: 11.5
+	};
+
+	!node.empty() && node.select("text")
+		.text("0")
+		.call(el => {
+			const box = el.node().getBBox();
+			const h = box.height;
+			const w = box.width;
+
+			if (h && w) {
+				size.h = h;
+				size.w = w;
+			}
+
+			el.text("");
+		});
+
+	return (getSizeFor1Char.size = size);
+};
+
 export default function(params = {}) {
 	let scale = d3ScaleLinear();
 	let orient = "bottom";
@@ -89,34 +120,6 @@ export default function(params = {}) {
 		return isDefined(formatted) ? formatted : "";
 	}
 
-	let getSizeFor1Char = tick => {
-		// default size for one character
-		const size = {
-			h: 11.5,
-			w: 5.5
-		};
-
-		!tick.empty() && tick.select("text")
-			.text("0")
-			.call(el => {
-				const box = el.node().getBBox();
-				const h = box.height;
-				const w = box.width;
-
-				if (h && w) {
-					size.h = h;
-					size.w = w;
-				}
-
-				el.text("");
-			});
-
-		// overwrite to return calculated size
-		getSizeFor1Char = () => size;
-
-		return size;
-	};
-
 	function transitionise(selection) {
 		return params.withoutTransition ?
 			selection.interrupt() : selection.transition(transition);
@@ -189,7 +192,7 @@ export default function(params = {}) {
 			}
 
 			let tspan;
-			const sizeFor1Char = getSizeFor1Char(g.select(".tick"));
+			const sizeFor1Char = getSizeFor1Char.size || getSizeFor1Char(g.select(".tick"));
 			const counts = [];
 			const tickLength = Math.max(innerTickSize, 0) + tickPadding;
 			const isVertical = orient === "left" || orient === "right";

src/internals/util.js

@@ -22,6 +22,8 @@ const isEmpty = o => (
 		(isString(o) && o.length === 0) ||
 		(isObjectType(o) && Object.keys(o).length === 0)
 );
+const notEmpty = o => !isEmpty(o);
+
 /**
  * Check if is array
  * @param {Array} arr
@@ -38,7 +40,6 @@ const isArray = arr => arr && arr.constructor === Array;
  */
 const isObject = obj => obj && !obj.nodeType && isObjectType(obj) && !isArray(obj);
 
-const notEmpty = o => !isEmpty(o);
 const getOption = (options, key, defaultValue) => (
 	isDefined(options[key]) ? options[key] : defaultValue
 );

yarn.lock

@@ -3176,6 +3176,13 @@ expand-tilde@^2.0.0, expand-tilde@^2.0.2:
   dependencies:
     homedir-polyfill "^1.0.1"
 
+exports-loader@^0.7.0:
+  version "0.7.0"
+  resolved "https://registry.yarnpkg.com/exports-loader/-/exports-loader-0.7.0.tgz#84881c784dea6036b8e1cd1dac3da9b6409e21a5"
+  dependencies:
+    loader-utils "^1.1.0"
+    source-map "0.5.0"
+
 express@^4.15.5, express@^4.16.2:
   version "4.16.3"
   resolved "https://registry.yarnpkg.com/express/-/express-4.16.3.tgz#6af8a502350db3246ecc4becf6b5a34d22f7ed53"
@@ -7835,6 +7842,10 @@ source-map-url@~0.3.0:
   version "0.3.0"
   resolved "https://registry.yarnpkg.com/source-map-url/-/source-map-url-0.3.0.tgz#7ecaf13b57bcd09da8a40c5d269db33799d4aaf9"
 
+[email protected]:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.0.tgz#0fe96503ac86a5adb5de63f4e412ae4872cdbe86"
+
 [email protected], source-map@^0.5.3, source-map@^0.5.6, source-map@^0.5.7, source-map@~0.5.1:
   version "0.5.7"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.7.tgz#8a039d2d1021d22d1ea14c80d8ea468ba2ef3fcc"