Make gaps equal when culling tick text

src/c3.axis.js

@@ -85,6 +85,38 @@ function c3_axis(d3, params, $$) {
         tickTextCharSize = size;
         return size;
     }
+    function hasIntersection (rect1, rect2) {
+        var r1x2 = rect1.x + rect1.width;
+        var r2x2 = rect2.x + rect2.width;
+        var r1y2 = rect1.y + rect1.height;
+        var r2y2 = rect2.y + rect2.height;
+
+        return (rect1.x < r2x2 && r1x2 > rect2.x &&
+                rect1.y < r2y2 && r1y2 > rect2.y);
+    }
+    function cullRects(rects){
+        if(rects.length < 2) return;
+
+        var cullGap = 0;
+        var i, j, l = rects.length;
+        for(i = 1, j = 0 ; i < l; i++){
+            if(hasIntersection(rects[i], rects[j])){
+                cullGap = Math.max(cullGap, i-j);
+            } else {
+                j = i;
+            }
+        }
+
+        if(!cullGap) return;
+
+        var cullStep = cullGap+1;
+
+        for(i = 0; i < l; i++){
+            if(i % cullStep){
+                rects[i] = null;
+            }
+        }
+    }
     function axis(g) {
         g.each(function () {
             var g = d3.select(this);
@@ -172,16 +204,6 @@ function c3_axis(d3, params, $$) {
                 return dy;
             }
 
-            function hasIntersection (rect1, rect2) {
-                var r1x2 = rect1.x + rect1.width;
-                var r2x2 = rect2.x + rect2.width;
-                var r1y2 = rect1.y + rect1.height;
-                var r2y2 = rect2.y + rect2.height;
-
-                return (rect1.x < r2x2 && r1x2 > rect2.x &&
-                        rect1.y < r2y2 && r1y2 > rect2.y);
-            }
-
             function tickSize(d) {
                 return innerTickSize;
             }
@@ -203,13 +225,6 @@ function c3_axis(d3, params, $$) {
             tspan.exit().remove();
 
             var axisId = $$.isXAxis(orient) ? 'x' : 'y';
-            var textClass = '.c3-axis-' + axisId + ' .tick'
-            var textRects = text.data().map(function(data) {
-                var rect = $$.getTextRect(textFormatted(data), textClass);
-                // Smaal additional padding between texts
-                rect.width += 10;
-                return rect;
-            });
 
             var fontSize = parseFloat(getStyleValue($$, '.c3-axis-y .tick', 'font-size'));
 
@@ -342,26 +357,22 @@ function c3_axis(d3, params, $$) {
                     break;
             }
 
-            var last = textRects.length - 1;
-
-            rectPositionFn(textRects[0], text.data()[0]);
-            rectPositionFn(textRects[last], text.data().pop());
-            
-            var addedTextRects = [textRects[0], textRects[last]];
-            text.style('display', function(d, i){
-                if(i === 0 || i === last) return 'block';
+            var textClass = '.c3-axis-' + axisId + ' .tick';
+            var textRects = text.data().map(function(data) {
+                var rect = $$.getTextRect(textFormatted(data), textClass);
+                // Smaal additional padding between texts
+                rect.width += 10;
+                return rect;
+            });
 
-                var rect = textRects[i];
-                rectPositionFn(rect, d);
-                var visible = !addedTextRects.some(function(added){
-                    return hasIntersection(rect, added);
+            text.each(function(d, i){
+                rectPositionFn(textRects[i], d);
             });
 
-                if(visible){
-                    addedTextRects.push(rect);
-                }
+            cullRects(textRects);
 
-                return visible ? 'block' : 'none';
+            text.style('display', function(d, i){
+                return textRects[i] === null ? 'none' : 'block'; 
             });
         });
     }