Lazily compute label sizes (#6351)

* Lazily compute label sizes

* Reduce file size

diff --git a/src/core/core.scale.js b/src/core/core.scale.js
index 298d409aa8ee76e93e868c6e605e83f35a4b006e..5eed97b9c7ba4661df163a298e8263e0823445be 100644 (file)
--- a/src/core/core.scale.js
+++ b/src/core/core.scale.js
@@ -257,6 +257,7 @@ var Scale = Element.extend({
                        bottom: 0
                }, margins);
 
+               me._labelSizes = null;
                me._maxLabelLines = 0;
                me.longestLabelWidth = 0;
                me.longestTextCache = me.longestTextCache || {};
@@ -419,31 +420,31 @@ var Scale = Element.extend({
                var labelRotation = minRotation;
                var labelSizes, maxLabelWidth, maxLabelHeight, maxWidth, tickWidth, maxHeight, maxLabelDiagonal;
 
-               if (me._isVisible() && tickOpts.display) {
-                       labelSizes = me._labelSizes = computeLabelSizes(me.ctx, parseTickFontOptions(tickOpts), ticks, me.longestTextCache);
-
-                       if (minRotation < maxRotation && ticks.length > 1 && me.isHorizontal()) {
-                               maxLabelWidth = labelSizes.widest.width;
-                               maxLabelHeight = labelSizes.highest.height - labelSizes.highest.offset;
-
-                               // Estimate the width of each grid based on the canvas width, the maximum
-                               // label width and the number of tick intervals
-                               maxWidth = Math.min(me.maxWidth, me.chart.width - maxLabelWidth);
-                               tickWidth = options.offset ? me.maxWidth / ticks.length : maxWidth / (ticks.length - 1);
-
-                               // Allow 3 pixels x2 padding either side for label readability
-                               if (maxLabelWidth + 6 > tickWidth) {
-                                       tickWidth = maxWidth / (ticks.length - (options.offset ? 0.5 : 1));
-                                       maxHeight = me.maxHeight - getTickMarkLength(options.gridLines)
-                                               - tickOpts.padding - getScaleLabelHeight(options.scaleLabel);
-                                       maxLabelDiagonal = Math.sqrt(maxLabelWidth * maxLabelWidth + maxLabelHeight * maxLabelHeight);
-                                       labelRotation = helpers.toDegrees(Math.min(
-                                               Math.asin(Math.min((labelSizes.highest.height + 6) / tickWidth, 1)),
-                                               Math.asin(Math.min(maxHeight / maxLabelDiagonal, 1)) - Math.asin(maxLabelHeight / maxLabelDiagonal)
-                                       ));
-                                       labelRotation = Math.max(minRotation, Math.min(maxRotation, labelRotation));
-                               }
-                       }
+               if (!me._isVisible() || !tickOpts.display || minRotation >= maxRotation || ticks.length <= 1 || !me.isHorizontal()) {
+                       me.labelRotation = minRotation;
+                       return;
+               }
+
+               labelSizes = me._getLabelSizes();
+               maxLabelWidth = labelSizes.widest.width;
+               maxLabelHeight = labelSizes.highest.height - labelSizes.highest.offset;
+
+               // Estimate the width of each grid based on the canvas width, the maximum
+               // label width and the number of tick intervals
+               maxWidth = Math.min(me.maxWidth, me.chart.width - maxLabelWidth);
+               tickWidth = options.offset ? me.maxWidth / ticks.length : maxWidth / (ticks.length - 1);
+
+               // Allow 3 pixels x2 padding either side for label readability
+               if (maxLabelWidth + 6 > tickWidth) {
+                       tickWidth = maxWidth / (ticks.length - (options.offset ? 0.5 : 1));
+                       maxHeight = me.maxHeight - getTickMarkLength(options.gridLines)
+                               - tickOpts.padding - getScaleLabelHeight(options.scaleLabel);
+                       maxLabelDiagonal = Math.sqrt(maxLabelWidth * maxLabelWidth + maxLabelHeight * maxLabelHeight);
+                       labelRotation = helpers.toDegrees(Math.min(
+                               Math.asin(Math.min((labelSizes.highest.height + 6) / tickWidth, 1)),
+                               Math.asin(Math.min(maxHeight / maxLabelDiagonal, 1)) - Math.asin(maxLabelHeight / maxLabelDiagonal)
+                       ));
+                       labelRotation = Math.max(minRotation, Math.min(maxRotation, labelRotation));
                }
 
                me.labelRotation = labelRotation;
@@ -491,7 +492,7 @@ var Scale = Element.extend({
                // Don't bother fitting the ticks if we are not showing the labels
                if (tickOpts.display && display) {
                        var tickFonts = parseTickFontOptions(tickOpts);
-                       var labelSizes = me._labelSizes;
+                       var labelSizes = me._getLabelSizes();
                        var firstLabelSize = labelSizes.first;
                        var lastLabelSize = labelSizes.last;
                        var widestLabelSize = labelSizes.widest;
@@ -501,8 +502,6 @@ var Scale = Element.extend({
 
                        if (isHorizontal) {
                                // A horizontal axis is more constrained by the height.
-                               me.longestLabelWidth = widestLabelSize.width;
-
                                var isRotated = me.labelRotation !== 0;
                                var angleRadians = helpers.toRadians(me.labelRotation);
                                var cosRotation = Math.cos(angleRadians);
@@ -610,8 +609,23 @@ var Scale = Element.extend({
        },
 
        /**
-       * @private
-       */
+        * @private
+        */
+       _getLabelSizes: function() {
+               var me = this;
+               var labelSizes = me._labelSizes;
+
+               if (!labelSizes) {
+                       me._labelSizes = labelSizes = computeLabelSizes(me.ctx, parseTickFontOptions(me.options.ticks), me.getTicks(), me.longestTextCache);
+                       me.longestLabelWidth = labelSizes.widest.width;
+               }
+
+               return labelSizes;
+       },
+
+       /**
+        * @private
+        */
        _parseValue: function(value) {
                var start, end, min, max;
 
@@ -782,7 +796,7 @@ var Scale = Element.extend({
                var cos = Math.abs(Math.cos(rot));
                var sin = Math.abs(Math.sin(rot));
 
-               var labelSizes = me._labelSizes;
+               var labelSizes = me._getLabelSizes();
                var padding = optionTicks.autoSkipPadding || 0;
                var w = labelSizes ? labelSizes.widest.width + padding : 0;
                var h = labelSizes ? labelSizes.highest.height + padding : 0;