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core.scale.js
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core.scale.js
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'use strict';
var defaults = require('./core.defaults');
var Element = require('./core.element');
var helpers = require('../helpers/index');
var Ticks = require('./core.ticks');
var isArray = helpers.isArray;
var isNullOrUndef = helpers.isNullOrUndef;
var valueOrDefault = helpers.valueOrDefault;
var valueAtIndexOrDefault = helpers.valueAtIndexOrDefault;
defaults._set('scale', {
display: true,
position: 'left',
offset: false,
// grid line settings
gridLines: {
display: true,
color: 'rgba(0,0,0,0.1)',
lineWidth: 1,
drawBorder: true,
drawOnChartArea: true,
drawTicks: true,
tickMarkLength: 10,
zeroLineWidth: 1,
zeroLineColor: 'rgba(0,0,0,0.25)',
zeroLineBorderDash: [],
zeroLineBorderDashOffset: 0.0,
offsetGridLines: false,
borderDash: [],
borderDashOffset: 0.0
},
// scale label
scaleLabel: {
// display property
display: false,
// actual label
labelString: '',
// top/bottom padding
padding: {
top: 4,
bottom: 4
}
},
// label settings
ticks: {
beginAtZero: false,
minRotation: 0,
maxRotation: 50,
mirror: false,
padding: 0,
reverse: false,
display: true,
autoSkip: true,
autoSkipPadding: 0,
labelOffset: 0,
// We pass through arrays to be rendered as multiline labels, we convert Others to strings here.
callback: Ticks.formatters.values,
minor: {},
major: {}
}
});
/** Returns a new array containing numItems from arr */
function sample(arr, numItems) {
var result = [];
var increment = arr.length / numItems;
var i = 0;
var len = arr.length;
for (; i < len; i += increment) {
result.push(arr[Math.floor(i)]);
}
return result;
}
function getPixelForGridLine(scale, index, offsetGridLines) {
var length = scale.getTicks().length;
var validIndex = Math.min(index, length - 1);
var lineValue = scale.getPixelForTick(validIndex);
var start = scale._startPixel;
var end = scale._endPixel;
var epsilon = 1e-6; // 1e-6 is margin in pixels for accumulated error.
var offset;
if (offsetGridLines) {
if (length === 1) {
offset = Math.max(lineValue - start, end - lineValue);
} else if (index === 0) {
offset = (scale.getPixelForTick(1) - lineValue) / 2;
} else {
offset = (lineValue - scale.getPixelForTick(validIndex - 1)) / 2;
}
lineValue += validIndex < index ? offset : -offset;
// Return undefined if the pixel is out of the range
if (lineValue < start - epsilon || lineValue > end + epsilon) {
return;
}
}
return lineValue;
}
function garbageCollect(caches, length) {
helpers.each(caches, function(cache) {
var gc = cache.gc;
var gcLen = gc.length / 2;
var i;
if (gcLen > length) {
for (i = 0; i < gcLen; ++i) {
delete cache.data[gc[i]];
}
gc.splice(0, gcLen);
}
});
}
/**
* Returns {width, height, offset} objects for the first, last, widest, highest tick
* labels where offset indicates the anchor point offset from the top in pixels.
*/
function computeLabelSizes(ctx, tickFonts, ticks, caches) {
var length = ticks.length;
var widths = [];
var heights = [];
var offsets = [];
var i, j, jlen, label, tickFont, fontString, cache, lineHeight, width, height, nestedLabel, widest, highest;
for (i = 0; i < length; ++i) {
label = ticks[i].label;
tickFont = ticks[i].major ? tickFonts.major : tickFonts.minor;
ctx.font = fontString = tickFont.string;
cache = caches[fontString] = caches[fontString] || {data: {}, gc: []};
lineHeight = tickFont.lineHeight;
width = height = 0;
// Undefined labels and arrays should not be measured
if (!isNullOrUndef(label) && !isArray(label)) {
width = helpers.measureText(ctx, cache.data, cache.gc, width, label);
height = lineHeight;
} else if (isArray(label)) {
// if it is an array let's measure each element
for (j = 0, jlen = label.length; j < jlen; ++j) {
nestedLabel = label[j];
// Undefined labels and arrays should not be measured
if (!isNullOrUndef(nestedLabel) && !isArray(nestedLabel)) {
width = helpers.measureText(ctx, cache.data, cache.gc, width, nestedLabel);
height += lineHeight;
}
}
}
widths.push(width);
heights.push(height);
offsets.push(lineHeight / 2);
}
garbageCollect(caches, length);
widest = widths.indexOf(Math.max.apply(null, widths));
highest = heights.indexOf(Math.max.apply(null, heights));
function valueAt(idx) {
return {
width: widths[idx] || 0,
height: heights[idx] || 0,
offset: offsets[idx] || 0
};
}
return {
first: valueAt(0),
last: valueAt(length - 1),
widest: valueAt(widest),
highest: valueAt(highest)
};
}
function getTickMarkLength(options) {
return options.drawTicks ? options.tickMarkLength : 0;
}
function getScaleLabelHeight(options) {
var font, padding;
if (!options.display) {
return 0;
}
font = helpers.options._parseFont(options);
padding = helpers.options.toPadding(options.padding);
return font.lineHeight + padding.height;
}
function parseFontOptions(options, nestedOpts) {
return helpers.extend(helpers.options._parseFont({
fontFamily: valueOrDefault(nestedOpts.fontFamily, options.fontFamily),
fontSize: valueOrDefault(nestedOpts.fontSize, options.fontSize),
fontStyle: valueOrDefault(nestedOpts.fontStyle, options.fontStyle),
lineHeight: valueOrDefault(nestedOpts.lineHeight, options.lineHeight)
}), {
color: helpers.options.resolve([nestedOpts.fontColor, options.fontColor, defaults.global.defaultFontColor])
});
}
function parseTickFontOptions(options) {
var minor = parseFontOptions(options, options.minor);
var major = options.major.enabled ? parseFontOptions(options, options.major) : minor;
return {minor: minor, major: major};
}
function nonSkipped(ticksToFilter) {
var filtered = [];
var item, index, len;
for (index = 0, len = ticksToFilter.length; index < len; ++index) {
item = ticksToFilter[index];
if (typeof item._index !== 'undefined') {
filtered.push(item);
}
}
return filtered;
}
function getEvenSpacing(arr) {
var len = arr.length;
var i, diff;
if (len < 2) {
return false;
}
for (diff = arr[0], i = 1; i < len; ++i) {
if (arr[i] - arr[i - 1] !== diff) {
return false;
}
}
return diff;
}
function calculateSpacing(majorIndices, ticks, axisLength, ticksLimit) {
var evenMajorSpacing = getEvenSpacing(majorIndices);
var spacing = (ticks.length - 1) / ticksLimit;
var factors, factor, i, ilen;
// If the major ticks are evenly spaced apart, place the minor ticks
// so that they divide the major ticks into even chunks
if (!evenMajorSpacing) {
return Math.max(spacing, 1);
}
factors = helpers.math._factorize(evenMajorSpacing);
for (i = 0, ilen = factors.length - 1; i < ilen; i++) {
factor = factors[i];
if (factor > spacing) {
return factor;
}
}
return Math.max(spacing, 1);
}
function getMajorIndices(ticks) {
var result = [];
var i, ilen;
for (i = 0, ilen = ticks.length; i < ilen; i++) {
if (ticks[i].major) {
result.push(i);
}
}
return result;
}
function skipMajors(ticks, majorIndices, spacing) {
var count = 0;
var next = majorIndices[0];
var i, tick;
spacing = Math.ceil(spacing);
for (i = 0; i < ticks.length; i++) {
tick = ticks[i];
if (i === next) {
tick._index = i;
count++;
next = majorIndices[count * spacing];
} else {
delete tick.label;
}
}
}
function skip(ticks, spacing, majorStart, majorEnd) {
var start = valueOrDefault(majorStart, 0);
var end = Math.min(valueOrDefault(majorEnd, ticks.length), ticks.length);
var count = 0;
var length, i, tick, next;
spacing = Math.ceil(spacing);
if (majorEnd) {
length = majorEnd - majorStart;
spacing = length / Math.floor(length / spacing);
}
next = start;
for (i = Math.max(start, 0); i < end; i++) {
tick = ticks[i];
if (i === next) {
tick._index = i;
count++;
next = Math.round(start + count * spacing);
} else {
delete tick.label;
}
}
}
var Scale = Element.extend({
zeroLineIndex: 0,
/**
* Get the padding needed for the scale
* @method getPadding
* @private
* @returns {Padding} the necessary padding
*/
getPadding: function() {
var me = this;
return {
left: me.paddingLeft || 0,
top: me.paddingTop || 0,
right: me.paddingRight || 0,
bottom: me.paddingBottom || 0
};
},
/**
* Returns the scale tick objects ({label, major})
* @since 2.7
*/
getTicks: function() {
return this._ticks;
},
/**
* @private
*/
_getLabels: function() {
var data = this.chart.data;
return this.options.labels || (this.isHorizontal() ? data.xLabels : data.yLabels) || data.labels;
},
// These methods are ordered by lifecyle. Utilities then follow.
// Any function defined here is inherited by all scale types.
// Any function can be extended by the scale type
/**
* Provided for backward compatibility, not available anymore
* @function Chart.Scale.mergeTicksOptions
* @deprecated since version 2.8.0
* @todo remove at version 3
*/
mergeTicksOptions: function() {
// noop
},
beforeUpdate: function() {
helpers.callback(this.options.beforeUpdate, [this]);
},
/**
* @param {number} maxWidth - the max width in pixels
* @param {number} maxHeight - the max height in pixels
* @param {object} margins - the space between the edge of the other scales and edge of the chart
* This space comes from two sources:
* - padding - space that's required to show the labels at the edges of the scale
* - thickness of scales or legends in another orientation
*/
update: function(maxWidth, maxHeight, margins) {
var me = this;
var tickOpts = me.options.ticks;
var sampleSize = tickOpts.sampleSize;
var i, ilen, labels, ticks, samplingEnabled;
// Update Lifecycle - Probably don't want to ever extend or overwrite this function ;)
me.beforeUpdate();
// Absorb the master measurements
me.maxWidth = maxWidth;
me.maxHeight = maxHeight;
me.margins = helpers.extend({
left: 0,
right: 0,
top: 0,
bottom: 0
}, margins);
me._ticks = null;
me.ticks = null;
me._labelSizes = null;
me._maxLabelLines = 0;
me.longestLabelWidth = 0;
me.longestTextCache = me.longestTextCache || {};
me._gridLineItems = null;
me._labelItems = null;
// Dimensions
me.beforeSetDimensions();
me.setDimensions();
me.afterSetDimensions();
// Data min/max
me.beforeDataLimits();
me.determineDataLimits();
me.afterDataLimits();
// Ticks - `this.ticks` is now DEPRECATED!
// Internal ticks are now stored as objects in the PRIVATE `this._ticks` member
// and must not be accessed directly from outside this class. `this.ticks` being
// around for long time and not marked as private, we can't change its structure
// without unexpected breaking changes. If you need to access the scale ticks,
// use scale.getTicks() instead.
me.beforeBuildTicks();
// New implementations should return an array of objects but for BACKWARD COMPAT,
// we still support no return (`this.ticks` internally set by calling this method).
ticks = me.buildTicks() || [];
// Allow modification of ticks in callback.
ticks = me.afterBuildTicks(ticks) || ticks;
// Ensure ticks contains ticks in new tick format
if ((!ticks || !ticks.length) && me.ticks) {
ticks = [];
for (i = 0, ilen = me.ticks.length; i < ilen; ++i) {
ticks.push({
value: me.ticks[i],
major: false
});
}
}
me._ticks = ticks;
// Compute tick rotation and fit using a sampled subset of labels
// We generally don't need to compute the size of every single label for determining scale size
samplingEnabled = sampleSize > ticks.length;
labels = me._convertTicksToLabels(samplingEnabled ? sample(ticks, sampleSize) : ticks);
// _configure is called twice, once here, once from core.controller.updateLayout.
// Here we haven't been positioned yet, but dimensions are correct.
// Variables set in _configure are needed for calculateTickRotation, and
// it's ok that coordinates are not correct there, only dimensions matter.
me._configure();
// Tick Rotation
me.beforeCalculateTickRotation();
me.calculateTickRotation();
me.afterCalculateTickRotation();
me.beforeFit();
me.fit();
me.afterFit();
// Auto-skip
me._ticksToDraw = tickOpts.display && (tickOpts.autoSkip || tickOpts.source === 'auto') ? me._autoSkip(ticks) : ticks;
if (samplingEnabled) {
// Generate labels using all non-skipped ticks
labels = me._convertTicksToLabels(me._ticksToDraw);
}
me.ticks = labels; // BACKWARD COMPATIBILITY
// IMPORTANT: after this point, we consider that `this.ticks` will NEVER change!
me.afterUpdate();
// TODO(v3): remove minSize as a public property and return value from all layout boxes. It is unused
// make maxWidth and maxHeight private
return me.minSize;
},
/**
* @private
*/
_configure: function() {
var me = this;
var reversePixels = me.options.ticks.reverse;
var startPixel, endPixel;
if (me.isHorizontal()) {
startPixel = me.left;
endPixel = me.right;
} else {
startPixel = me.top;
endPixel = me.bottom;
// by default vertical scales are from bottom to top, so pixels are reversed
reversePixels = !reversePixels;
}
me._startPixel = startPixel;
me._endPixel = endPixel;
me._reversePixels = reversePixels;
me._length = endPixel - startPixel;
},
afterUpdate: function() {
helpers.callback(this.options.afterUpdate, [this]);
},
//
beforeSetDimensions: function() {
helpers.callback(this.options.beforeSetDimensions, [this]);
},
setDimensions: function() {
var me = this;
// Set the unconstrained dimension before label rotation
if (me.isHorizontal()) {
// Reset position before calculating rotation
me.width = me.maxWidth;
me.left = 0;
me.right = me.width;
} else {
me.height = me.maxHeight;
// Reset position before calculating rotation
me.top = 0;
me.bottom = me.height;
}
// Reset padding
me.paddingLeft = 0;
me.paddingTop = 0;
me.paddingRight = 0;
me.paddingBottom = 0;
},
afterSetDimensions: function() {
helpers.callback(this.options.afterSetDimensions, [this]);
},
// Data limits
beforeDataLimits: function() {
helpers.callback(this.options.beforeDataLimits, [this]);
},
determineDataLimits: helpers.noop,
afterDataLimits: function() {
helpers.callback(this.options.afterDataLimits, [this]);
},
//
beforeBuildTicks: function() {
helpers.callback(this.options.beforeBuildTicks, [this]);
},
buildTicks: helpers.noop,
afterBuildTicks: function(ticks) {
var me = this;
// ticks is empty for old axis implementations here
if (isArray(ticks) && ticks.length) {
return helpers.callback(me.options.afterBuildTicks, [me, ticks]);
}
// Support old implementations (that modified `this.ticks` directly in buildTicks)
me.ticks = helpers.callback(me.options.afterBuildTicks, [me, me.ticks]) || me.ticks;
return ticks;
},
beforeTickToLabelConversion: function() {
helpers.callback(this.options.beforeTickToLabelConversion, [this]);
},
convertTicksToLabels: function() {
var me = this;
// Convert ticks to strings
var tickOpts = me.options.ticks;
me.ticks = me.ticks.map(tickOpts.userCallback || tickOpts.callback, this);
},
afterTickToLabelConversion: function() {
helpers.callback(this.options.afterTickToLabelConversion, [this]);
},
//
beforeCalculateTickRotation: function() {
helpers.callback(this.options.beforeCalculateTickRotation, [this]);
},
calculateTickRotation: function() {
var me = this;
var options = me.options;
var tickOpts = options.ticks;
var numTicks = me.getTicks().length;
var minRotation = tickOpts.minRotation || 0;
var maxRotation = tickOpts.maxRotation;
var labelRotation = minRotation;
var labelSizes, maxLabelWidth, maxLabelHeight, maxWidth, tickWidth, maxHeight, maxLabelDiagonal;
if (!me._isVisible() || !tickOpts.display || minRotation >= maxRotation || numTicks <= 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 / numTicks : maxWidth / (numTicks - 1);
// Allow 3 pixels x2 padding either side for label readability
if (maxLabelWidth + 6 > tickWidth) {
tickWidth = maxWidth / (numTicks - (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;
},
afterCalculateTickRotation: function() {
helpers.callback(this.options.afterCalculateTickRotation, [this]);
},
//
beforeFit: function() {
helpers.callback(this.options.beforeFit, [this]);
},
fit: function() {
var me = this;
// Reset
var minSize = me.minSize = {
width: 0,
height: 0
};
var chart = me.chart;
var opts = me.options;
var tickOpts = opts.ticks;
var scaleLabelOpts = opts.scaleLabel;
var gridLineOpts = opts.gridLines;
var display = me._isVisible();
var isBottom = opts.position === 'bottom';
var isHorizontal = me.isHorizontal();
// Width
if (isHorizontal) {
minSize.width = me.maxWidth;
} else if (display) {
minSize.width = getTickMarkLength(gridLineOpts) + getScaleLabelHeight(scaleLabelOpts);
}
// height
if (!isHorizontal) {
minSize.height = me.maxHeight; // fill all the height
} else if (display) {
minSize.height = getTickMarkLength(gridLineOpts) + getScaleLabelHeight(scaleLabelOpts);
}
// Don't bother fitting the ticks if we are not showing the labels
if (tickOpts.display && display) {
var tickFonts = parseTickFontOptions(tickOpts);
var labelSizes = me._getLabelSizes();
var firstLabelSize = labelSizes.first;
var lastLabelSize = labelSizes.last;
var widestLabelSize = labelSizes.widest;
var highestLabelSize = labelSizes.highest;
var lineSpace = tickFonts.minor.lineHeight * 0.4;
var tickPadding = tickOpts.padding;
if (isHorizontal) {
// A horizontal axis is more constrained by the height.
var isRotated = me.labelRotation !== 0;
var angleRadians = helpers.toRadians(me.labelRotation);
var cosRotation = Math.cos(angleRadians);
var sinRotation = Math.sin(angleRadians);
var labelHeight = sinRotation * widestLabelSize.width
+ cosRotation * (highestLabelSize.height - (isRotated ? highestLabelSize.offset : 0))
+ (isRotated ? 0 : lineSpace); // padding
minSize.height = Math.min(me.maxHeight, minSize.height + labelHeight + tickPadding);
var offsetLeft = me.getPixelForTick(0) - me.left;
var offsetRight = me.right - me.getPixelForTick(me.getTicks().length - 1);
var paddingLeft, paddingRight;
// Ensure that our ticks are always inside the canvas. When rotated, ticks are right aligned
// which means that the right padding is dominated by the font height
if (isRotated) {
paddingLeft = isBottom ?
cosRotation * firstLabelSize.width + sinRotation * firstLabelSize.offset :
sinRotation * (firstLabelSize.height - firstLabelSize.offset);
paddingRight = isBottom ?
sinRotation * (lastLabelSize.height - lastLabelSize.offset) :
cosRotation * lastLabelSize.width + sinRotation * lastLabelSize.offset;
} else {
paddingLeft = firstLabelSize.width / 2;
paddingRight = lastLabelSize.width / 2;
}
// Adjust padding taking into account changes in offsets
// and add 3 px to move away from canvas edges
me.paddingLeft = Math.max((paddingLeft - offsetLeft) * me.width / (me.width - offsetLeft), 0) + 3;
me.paddingRight = Math.max((paddingRight - offsetRight) * me.width / (me.width - offsetRight), 0) + 3;
} else {
// A vertical axis is more constrained by the width. Labels are the
// dominant factor here, so get that length first and account for padding
var labelWidth = tickOpts.mirror ? 0 :
// use lineSpace for consistency with horizontal axis
// tickPadding is not implemented for horizontal
widestLabelSize.width + tickPadding + lineSpace;
minSize.width = Math.min(me.maxWidth, minSize.width + labelWidth);
me.paddingTop = firstLabelSize.height / 2;
me.paddingBottom = lastLabelSize.height / 2;
}
}
me.handleMargins();
if (isHorizontal) {
me.width = me._length = chart.width - me.margins.left - me.margins.right;
me.height = minSize.height;
} else {
me.width = minSize.width;
me.height = me._length = chart.height - me.margins.top - me.margins.bottom;
}
},
/**
* Handle margins and padding interactions
* @private
*/
handleMargins: function() {
var me = this;
if (me.margins) {
me.margins.left = Math.max(me.paddingLeft, me.margins.left);
me.margins.top = Math.max(me.paddingTop, me.margins.top);
me.margins.right = Math.max(me.paddingRight, me.margins.right);
me.margins.bottom = Math.max(me.paddingBottom, me.margins.bottom);
}
},
afterFit: function() {
helpers.callback(this.options.afterFit, [this]);
},
// Shared Methods
isHorizontal: function() {
var pos = this.options.position;
return pos === 'top' || pos === 'bottom';
},
isFullWidth: function() {
return this.options.fullWidth;
},
// Get the correct value. NaN bad inputs, If the value type is object get the x or y based on whether we are horizontal or not
getRightValue: function(rawValue) {
// Null and undefined values first
if (isNullOrUndef(rawValue)) {
return NaN;
}
// isNaN(object) returns true, so make sure NaN is checking for a number; Discard Infinite values
if ((typeof rawValue === 'number' || rawValue instanceof Number) && !isFinite(rawValue)) {
return NaN;
}
// If it is in fact an object, dive in one more level
if (rawValue) {
if (this.isHorizontal()) {
if (rawValue.x !== undefined) {
return this.getRightValue(rawValue.x);
}
} else if (rawValue.y !== undefined) {
return this.getRightValue(rawValue.y);
}
}
// Value is good, return it
return rawValue;
},
_convertTicksToLabels: function(ticks) {
var me = this;
var labels, i, ilen;
me.ticks = ticks.map(function(tick) {
return tick.value;
});
me.beforeTickToLabelConversion();
// New implementations should return the formatted tick labels but for BACKWARD
// COMPAT, we still support no return (`this.ticks` internally changed by calling
// this method and supposed to contain only string values).
labels = me.convertTicksToLabels(ticks) || me.ticks;
me.afterTickToLabelConversion();
// BACKWARD COMPAT: synchronize `_ticks` with labels (so potentially `this.ticks`)
for (i = 0, ilen = ticks.length; i < ilen; ++i) {
ticks[i].label = labels[i];
}
return labels;
},
/**
* @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;
if (isArray(value)) {
start = +this.getRightValue(value[0]);
end = +this.getRightValue(value[1]);
min = Math.min(start, end);
max = Math.max(start, end);
} else {
value = +this.getRightValue(value);
start = undefined;
end = value;
min = value;
max = value;
}
return {
min: min,
max: max,
start: start,
end: end
};
},
/**
* @private
*/
_getScaleLabel: function(rawValue) {
var v = this._parseValue(rawValue);
if (v.start !== undefined) {
return '[' + v.start + ', ' + v.end + ']';
}
return +this.getRightValue(rawValue);
},
/**
* Used to get the value to display in the tooltip for the data at the given index
* @param index
* @param datasetIndex
*/
getLabelForIndex: helpers.noop,
/**
* Returns the location of the given data point. Value can either be an index or a numerical value
* The coordinate (0, 0) is at the upper-left corner of the canvas
* @param value
* @param index
* @param datasetIndex
*/
getPixelForValue: helpers.noop,
/**
* Used to get the data value from a given pixel. This is the inverse of getPixelForValue
* The coordinate (0, 0) is at the upper-left corner of the canvas
* @param pixel
*/
getValueForPixel: helpers.noop,
/**
* Returns the location of the tick at the given index
* The coordinate (0, 0) is at the upper-left corner of the canvas
*/
getPixelForTick: function(index) {
var me = this;
var offset = me.options.offset;
var numTicks = me._ticks.length;
var tickWidth = 1 / Math.max(numTicks - (offset ? 0 : 1), 1);
return index < 0 || index > numTicks - 1
? null
: me.getPixelForDecimal(index * tickWidth + (offset ? tickWidth / 2 : 0));
},
/**
* Utility for getting the pixel location of a percentage of scale
* The coordinate (0, 0) is at the upper-left corner of the canvas
*/
getPixelForDecimal: function(decimal) {
var me = this;
if (me._reversePixels) {
decimal = 1 - decimal;
}
return me._startPixel + decimal * me._length;
},
getDecimalForPixel: function(pixel) {
var decimal = (pixel - this._startPixel) / this._length;
return Math.min(1, Math.max(0, this._reversePixels ? 1 - decimal : decimal));
},
/**
* Returns the pixel for the minimum chart value
* The coordinate (0, 0) is at the upper-left corner of the canvas
*/
getBasePixel: function() {
return this.getPixelForValue(this.getBaseValue());
},
getBaseValue: function() {
var me = this;
var min = me.min;
var max = me.max;
return me.beginAtZero ? 0 :
min < 0 && max < 0 ? max :
min > 0 && max > 0 ? min :
0;
},
/**
* Returns a subset of ticks to be plotted to avoid overlapping labels.
* @private
*/
_autoSkip: function(ticks) {
var me = this;
var tickOpts = me.options.ticks;
var axisLength = me._length;
var ticksLimit = tickOpts.maxTicksLimit || axisLength / me._tickSize() + 1;
var majorIndices = tickOpts.major.enabled ? getMajorIndices(ticks) : [];
var numMajorIndices = majorIndices.length;
var first = majorIndices[0];
var last = majorIndices[numMajorIndices - 1];
var i, ilen, spacing, avgMajorSpacing;
// If there are too many major ticks to display them all
if (numMajorIndices > ticksLimit) {
skipMajors(ticks, majorIndices, numMajorIndices / ticksLimit);
return nonSkipped(ticks);
}
spacing = calculateSpacing(majorIndices, ticks, axisLength, ticksLimit);
if (numMajorIndices > 0) {
for (i = 0, ilen = numMajorIndices - 1; i < ilen; i++) {
skip(ticks, spacing, majorIndices[i], majorIndices[i + 1]);
}
avgMajorSpacing = numMajorIndices > 1 ? (last - first) / (numMajorIndices - 1) : null;
skip(ticks, spacing, helpers.isNullOrUndef(avgMajorSpacing) ? 0 : first - avgMajorSpacing, first);
skip(ticks, spacing, last, helpers.isNullOrUndef(avgMajorSpacing) ? ticks.length : last + avgMajorSpacing);
return nonSkipped(ticks);
}
skip(ticks, spacing);
return nonSkipped(ticks);
},
/**
* @private
*/
_tickSize: function() {
var me = this;
var optionTicks = me.options.ticks;
// Calculate space needed by label in axis direction.
var rot = helpers.toRadians(me.labelRotation);
var cos = Math.abs(Math.cos(rot));
var sin = Math.abs(Math.sin(rot));
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;