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Fix offsetGridLine behavior with a single data point #5609

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merged 1 commit into from Nov 2, 2018
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Fix offsetGridLine behavior with a single data point #5609

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12 changes: 8 additions & 4 deletions src/core/core.scale.js
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Expand Up @@ -76,11 +76,15 @@ function labelsFromTicks(ticks) {
return labels;
}

function getLineValue(scale, index, offsetGridLines) {
function getPixelForGridLine(scale, index, offsetGridLines) {
var lineValue = scale.getPixelForTick(index);

if (offsetGridLines) {
if (index === 0) {
if (scale.getTicks().length === 1) {
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lineValue -= scale.isHorizontal() ?
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I think this draws a line on top of the axis? The axis looks extra dark in your images, which further reinforces my reading of this code. Perhaps it should return null instead and then not draw the line in that case

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Yes, it draws a line on top of the axis, but this is not a special case as you can see in this official example (the y axis looks extra dark depending on the canvas width). This can be fixed by checking if the line and the axis border are overlapping, but wouldn't it be better to open a different PR?

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It'd be an easy change:

var xLineValue = getPixelForGridLine(me, index, gridLines.offsetGridLines);
if (helpers.isNullOrUndef(xLineValue)) {
    return;
}

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@nagix nagix Aug 9, 2018 •
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This is a bit more complicated. If it returns here, not only the grid line but also the tick label will disappear as they are drawn together. That's why lineColor is set to transparent if the offset grid line is out of the range.

So, in order to avoid drawing the grid line over axis, we need to check whether each grid line is on the axis (this requires to check gridLines.drawBorder and options.position) and to set lineColor to transparent if needed.

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Ah, right you are. Ok, in that case, I agree with you that it's complicated enough that it would perhaps be better handled in another PR instead. Thanks for the clarification

Math.max(lineValue - scale.left, scale.right - lineValue) :
Math.max(lineValue - scale.top, scale.bottom - lineValue);
} else if (index === 0) {
lineValue -= (scale.getPixelForTick(1) - lineValue) / 2;
} else {
lineValue -= (lineValue - scale.getPixelForTick(index - 1)) / 2;
Expand Down Expand Up @@ -754,7 +758,7 @@ module.exports = Element.extend({
labelY = me.bottom - labelYOffset;
}

var xLineValue = getLineValue(me, index, gridLines.offsetGridLines && ticks.length > 1);
var xLineValue = getPixelForGridLine(me, index, gridLines.offsetGridLines);
if (xLineValue < me.left - epsilon) {
lineColor = 'rgba(0,0,0,0)';
}
Expand All @@ -781,7 +785,7 @@ module.exports = Element.extend({

labelX = isLeft ? me.right - labelXOffset : me.left + labelXOffset;

var yLineValue = getLineValue(me, index, gridLines.offsetGridLines && ticks.length > 1);
var yLineValue = getPixelForGridLine(me, index, gridLines.offsetGridLines);
if (yLineValue < me.top - epsilon) {
lineColor = 'rgba(0,0,0,0)';
}
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133 changes: 133 additions & 0 deletions test/specs/core.scale.tests.js
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Expand Up @@ -19,4 +19,137 @@ describe('Core.scale', function() {
}
});
});

var gridLineTests = [{
labels: ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'],
offsetGridLines: false,
offset: false,
expected: [0.5, 128.5, 256.5, 384.5, 512.5]
}, {
labels: ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'],
offsetGridLines: false,
offset: true,
expected: [51.5, 154.5, 256.5, 358.5, 461.5]
}, {
labels: ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'],
offsetGridLines: true,
offset: false,
expected: [-63.5, 64.5, 192.5, 320.5, 448.5]
}, {
labels: ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'],
offsetGridLines: true,
offset: true,
expected: [0, 103, 205.5, 307.5, 410]
}, {
labels: ['tick1'],
offsetGridLines: false,
offset: false,
expected: [0.5]
}, {
labels: ['tick1'],
offsetGridLines: false,
offset: true,
expected: [256.5]
}, {
labels: ['tick1'],
offsetGridLines: true,
offset: false,
expected: [-511.5]
}, {
labels: ['tick1'],
offsetGridLines: true,
offset: true,
expected: [0.5]
}];

gridLineTests.forEach(function(test) {
it('should get the correct pixels for ' + test.labels.length + ' gridLine(s) for the horizontal scale when offsetGridLines is ' + test.offsetGridLines + ' and offset is ' + test.offset, function() {
var chart = window.acquireChart({
type: 'line',
data: {
datasets: [{
data: []
}],
labels: test.labels
},
options: {
scales: {
xAxes: [{
id: 'xScale0',
gridLines: {
offsetGridLines: test.offsetGridLines,
drawTicks: false
},
ticks: {
display: false
},
offset: test.offset
}],
yAxes: [{
display: false
}]
},
legend: {
display: false
}
}
});

var xScale = chart.scales.xScale0;
xScale.ctx = window.createMockContext();
chart.draw();

expect(xScale.ctx.getCalls().filter(function(x) {
return x.name === 'moveTo' && x.args[1] === 0;
}).map(function(x) {
return x.args[0];
})).toEqual(test.expected);
});
});

gridLineTests.forEach(function(test) {
it('should get the correct pixels for ' + test.labels.length + ' gridLine(s) for the vertical scale when offsetGridLines is ' + test.offsetGridLines + ' and offset is ' + test.offset, function() {
var chart = window.acquireChart({
type: 'line',
data: {
datasets: [{
data: []
}],
labels: test.labels
},
options: {
scales: {
xAxes: [{
display: false
}],
yAxes: [{
type: 'category',
id: 'yScale0',
gridLines: {
offsetGridLines: test.offsetGridLines,
drawTicks: false
},
ticks: {
display: false
},
offset: test.offset
}]
},
legend: {
display: false
}
}
});

var yScale = chart.scales.yScale0;
yScale.ctx = window.createMockContext();
chart.draw();

expect(yScale.ctx.getCalls().filter(function(x) {
return x.name === 'moveTo' && x.args[0] === 0;
}).map(function(x) {
return x.args[1];
})).toEqual(test.expected);
});
});
});