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Lazily compute label sizes (#6351)
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* Lazily compute label sizes

* Reduce file size
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benmccann authored and etimberg committed Jun 27, 2019
1 parent d480e11 commit fb3d6ab
Showing 1 changed file with 45 additions and 31 deletions.
76 changes: 45 additions & 31 deletions src/core/core.scale.js
Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,7 @@ var Scale = Element.extend({
bottom: 0
}, margins);

me._labelSizes = null;
me._maxLabelLines = 0;
me.longestLabelWidth = 0;
me.longestTextCache = me.longestTextCache || {};
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand All @@ -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);
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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;
Expand Down

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