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Improve tick generation for linear scales #5938

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merged 3 commits into from Jan 1, 2019
Merged

Improve tick generation for linear scales #5938

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48aecb4
Improve tick generation for linear scales
nagix Dec 26, 2018
e33e1ff
Simplify the tick generation code
nagix Dec 28, 2018
e175645
Refactor getTickLimit
nagix Dec 29, 2018
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21 changes: 13 additions & 8 deletions src/scales/scale.linear.js
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@@ -1,6 +1,5 @@
'use strict';

var defaults = require('../core/core.defaults');
var helpers = require('../helpers/index');
var scaleService = require('../core/core.scaleService');
var Ticks = require('../core/core.ticks');
Expand Down Expand Up @@ -134,16 +133,22 @@ module.exports = function(Chart) {
this.handleTickRangeOptions();
},
getTickLimit: function() {
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var maxTicks;
var me = this;
var tickOpts = me.options.ticks;

if (me.isHorizontal()) {
maxTicks = Math.min(tickOpts.maxTicksLimit ? tickOpts.maxTicksLimit : 11, Math.ceil(me.width / 50));
var stepSize = tickOpts.stepSize;
var maxTicksLimit = tickOpts.maxTicksLimit;
var maxTicks, tickFont;

if (stepSize > 0) {
maxTicks = Math.ceil(me.max / stepSize) - Math.floor(me.min / stepSize) + 1;
} else if (me.isHorizontal()) {
maxTicks = Math.ceil(me.width / 40);
} else {
// The factor of 2 used to scale the font size has been experimentally determined.
var tickFontSize = helpers.valueOrDefault(tickOpts.fontSize, defaults.global.defaultFontSize);
maxTicks = Math.min(tickOpts.maxTicksLimit ? tickOpts.maxTicksLimit : 11, Math.ceil(me.height / (2 * tickFontSize)));
tickFont = helpers.options._parseFont(tickOpts);
maxTicks = Math.ceil(me.height / tickFont.lineHeight);
}
if (maxTicksLimit || !(stepSize > 0)) {
maxTicks = Math.min(maxTicksLimit || 11, maxTicks);
}

return maxTicks;
Expand Down
42 changes: 24 additions & 18 deletions src/scales/scale.linearbase.js
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Expand Up @@ -16,35 +16,41 @@ function generateTicks(generationOptions, dataRange) {
// for details.

var stepSize = generationOptions.stepSize;
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stepSize < 0 doesn't seems a valid value, so maybe we can simplify all these checks by clamping this value:

var stepSize = Math.max(0, generationOptions.stepSize);
var unit = stepSize || 1;
//...

var unit = stepSize > 0 ? stepSize : 1;
var maxNumSpaces = generationOptions.maxTicks - 1;
var min = generationOptions.min;
var max = generationOptions.max;
var spacing, precision, factor, niceRange, niceMin, niceMax, numSpaces;
var precision = generationOptions.precision;
var spacing, factor, niceMin, niceMax, numSpaces;

// spacing is set to a nice number of the dataRange divided by maxNumSpaces.
// stepSize is used as a minimum unit if it is specified.
spacing = helpers.niceNum((dataRange.max - dataRange.min) / maxNumSpaces / unit) * unit;
numSpaces = Math.ceil(dataRange.max / spacing) - Math.floor(dataRange.min / spacing);
if (numSpaces > maxNumSpaces) {
// If the calculated num of spaces exceeds maxNumSpaces, recalculate it
spacing = helpers.niceNum(numSpaces * spacing / maxNumSpaces / unit) * unit;
}

if (stepSize && stepSize > 0) {
spacing = stepSize;
if (!(stepSize > 0) && !helpers.isNullOrUndef(precision)) {
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// If the user specified a precision, round to that number of decimal places
factor = Math.pow(10, precision);
spacing = Math.ceil(spacing * factor) / factor;
} else {
niceRange = helpers.niceNum(dataRange.max - dataRange.min, false);
spacing = helpers.niceNum(niceRange / (generationOptions.maxTicks - 1), true);

precision = generationOptions.precision;
if (!helpers.isNullOrUndef(precision)) {
// If the user specified a precision, round to that number of decimal places
factor = Math.pow(10, precision);
spacing = Math.ceil(spacing * factor) / factor;
}
}
// If a precision is not specified, calculate factor based on spacing
if (!factor) {
// If a precision is not specified, calculate factor based on spacing
factor = Math.pow(10, helpers.decimalPlaces(spacing));
}

niceMin = Math.floor(dataRange.min / spacing) * spacing;
niceMax = Math.ceil(dataRange.max / spacing) * spacing;

// If min, max and stepSize is set and they make an evenly spaced scale use it.
if (!helpers.isNullOrUndef(min) && !helpers.isNullOrUndef(max) && stepSize) {
if (stepSize > 0) {
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// If very close to our whole number, use it.
if (helpers.almostWhole((max - min) / stepSize, spacing / 1000)) {
if (!helpers.isNullOrUndef(min) && helpers.almostWhole(min / spacing, spacing / 1000)) {
niceMin = min;
}
if (!helpers.isNullOrUndef(max) && helpers.almostWhole(max / spacing, spacing / 1000)) {
niceMax = max;
}
}
Expand Down Expand Up @@ -155,7 +161,7 @@ module.exports = function(Chart) {
var tickOpts = opts.ticks;

// Figure out what the max number of ticks we can support it is based on the size of
// the axis area. For now, we say that the minimum tick spacing in pixels must be 50
// the axis area. For now, we say that the minimum tick spacing in pixels must be 40
// We also limit the maximum number of ticks to 11 which gives a nice 10 squares on
// the graph. Make sure we always have at least 2 ticks
var maxTicks = me.getTickLimit();
Expand Down
4 changes: 0 additions & 4 deletions src/scales/scale.logarithmic.js
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Expand Up @@ -15,10 +15,6 @@ function generateTicks(generationOptions, dataRange) {
var ticks = [];
var valueOrDefault = helpers.valueOrDefault;

// Figure out what the max number of ticks we can support it is based on the size of
// the axis area. For now, we say that the minimum tick spacing in pixels must be 50
// We also limit the maximum number of ticks to 11 which gives a nice 10 squares on
// the graph
var tickVal = valueOrDefault(generationOptions.min, Math.pow(10, Math.floor(helpers.log10(dataRange.min))));

var endExp = Math.floor(helpers.log10(dataRange.max));
Expand Down
19 changes: 16 additions & 3 deletions src/scales/scale.radialLinear.js
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Expand Up @@ -358,10 +358,23 @@ module.exports = function(Chart) {
me.handleTickRangeOptions();
},
getTickLimit: function() {
var opts = this.options;
var me = this;
var opts = me.options;
var tickOpts = opts.ticks;
var tickBackdropHeight = getTickBackdropHeight(opts);
return Math.min(tickOpts.maxTicksLimit ? tickOpts.maxTicksLimit : 11, Math.ceil(this.drawingArea / tickBackdropHeight));
var stepSize = tickOpts.stepSize;
var maxTicksLimit = tickOpts.maxTicksLimit;
var maxTicks;

if (stepSize > 0) {
maxTicks = Math.ceil(me.max / stepSize) - Math.floor(me.min / stepSize) + 1;
} else {
maxTicks = Math.ceil(me.drawingArea / getTickBackdropHeight(opts));
}
if (maxTicksLimit || !(stepSize > 0)) {
maxTicks = Math.min(maxTicksLimit || 11, maxTicks);
}

return maxTicks;
},
convertTicksToLabels: function() {
var me = this;
Expand Down
49 changes: 48 additions & 1 deletion test/specs/scale.linear.tests.js
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Expand Up @@ -570,7 +570,7 @@ describe('Linear Scale', function() {
expect(chart.scales.yScale0).not.toEqual(undefined); // must construct
expect(chart.scales.yScale0.min).toBe(1);
expect(chart.scales.yScale0.max).toBe(11);
expect(chart.scales.yScale0.ticks).toEqual(['11', '9', '7', '5', '3', '1']);
expect(chart.scales.yScale0.ticks).toEqual(['11', '10', '8', '6', '4', '2', '1']);
});

it('Should create decimal steps if stepSize is a decimal number', function() {
Expand Down Expand Up @@ -749,6 +749,53 @@ describe('Linear Scale', function() {
expect(chart.scales.yScale0.ticks).toEqual(['0.06', '0.05', '0.04', '0.03', '0.02', '0.01', '0']);
});

it('Should correctly limit the maximum number of ticks', function() {
var chart = window.acquireChart({
type: 'bar',
data: {
labels: ['a', 'b'],
datasets: [{
data: [0.5, 2.5]
}]
},
options: {
scales: {
yAxes: [{
id: 'yScale'
}]
}
}
});

expect(chart.scales.yScale.ticks).toEqual(['2.5', '2.0', '1.5', '1.0', '0.5']);

chart.options.scales.yAxes[0].ticks.maxTicksLimit = 11;
chart.update();

expect(chart.scales.yScale.ticks).toEqual(['2.5', '2.0', '1.5', '1.0', '0.5']);

chart.options.scales.yAxes[0].ticks.maxTicksLimit = 21;
chart.update();

expect(chart.scales.yScale.ticks).toEqual([
'2.5', '2.4', '2.3', '2.2', '2.1', '2.0', '1.9', '1.8', '1.7', '1.6',
'1.5', '1.4', '1.3', '1.2', '1.1', '1.0', '0.9', '0.8', '0.7', '0.6',
'0.5'
]);

chart.options.scales.yAxes[0].ticks.maxTicksLimit = 11;
chart.options.scales.yAxes[0].ticks.stepSize = 0.01;
chart.update();

expect(chart.scales.yScale.ticks).toEqual(['2.5', '2.0', '1.5', '1.0', '0.5']);

chart.options.scales.yAxes[0].ticks.min = 0.3;
chart.options.scales.yAxes[0].ticks.max = 2.8;
chart.update();

expect(chart.scales.yScale.ticks).toEqual(['2.8', '2.5', '2.0', '1.5', '1.0', '0.5', '0.3']);
});

it('Should build labels using the user supplied callback', function() {
var chart = window.acquireChart({
type: 'bar',
Expand Down
37 changes: 37 additions & 0 deletions test/specs/scale.radialLinear.tests.js
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Expand Up @@ -282,6 +282,43 @@ describe('Test the radial linear scale', function() {
expect(chart.scale.end).toBe(0);
});

it('Should correctly limit the maximum number of ticks', function() {
var chart = window.acquireChart({
type: 'radar',
data: {
labels: ['label1', 'label2', 'label3'],
datasets: [{
data: [0.5, 1.5, 2.5]
}]
},
options: {
scale: {
pointLabels: {
display: false
}
}
}
});

expect(chart.scale.ticks).toEqual(['0.5', '1.0', '1.5', '2.0', '2.5']);

chart.options.scale.ticks.maxTicksLimit = 11;
chart.update();

expect(chart.scale.ticks).toEqual(['0.5', '1.0', '1.5', '2.0', '2.5']);

chart.options.scale.ticks.stepSize = 0.01;
chart.update();

expect(chart.scale.ticks).toEqual(['0.5', '1.0', '1.5', '2.0', '2.5']);

chart.options.scale.ticks.min = 0.3;
chart.options.scale.ticks.max = 2.8;
chart.update();

expect(chart.scale.ticks).toEqual(['0.3', '0.5', '1.0', '1.5', '2.0', '2.5', '2.8']);
});

it('Should build labels using the user supplied callback', function() {
var chart = window.acquireChart({
type: 'radar',
Expand Down