New component: Color scale legend

package.json

@@ -35,6 +35,7 @@
 		"d3-hierarchy": "^3.1.1",
 		"d3-quadtree": "^3.0.1",
 		"d3-sankey": "^0.12.3",
+		"d3-scale-chromatic": "^3.0.0",
 		"d3-time": "^3.0.0",
 		"d3-time-format": "^4.1.0",
 		"degit": "^2.8.4",

src/_components/ColorBar.html.svelte

@@ -0,0 +1,191 @@
+<!--
+	@component
+	Creates a color bar key for chromatic scales on `zScale`.
+ -->
+<script>
+	import { getContext } from 'svelte';
+
+	const { zScale } = getContext('LayerCake');
+
+	/** @type {string | null} [label=null] - Text label to show next to the color bar */
+	export let label = null;
+
+	/** @type {string} [labelSide='left'] - Position of the label. Can be 'top', 'right', 'bottom', or 'left
+	 * text label relative to the gradient bar */
+	export let labelSide = `left`;
+
+	/** @type {Number|Array|Function} [ticks=4] - If this is a number, it passes that along to the [d3Scale.ticks](https://github.com/d3/d3-scale) function. If this is an array, hardcodes the ticks to those values. If it's a function, passes along the default tick values and expects an array of tick values in return. */
+	export let ticks = 3;
+
+	/** @type {Boolean} [tickMarks=false] - Show a vertical mark for each tick. */
+	export let tickMarks = false;
+
+	/** @type {Function} [formatTick=d => d] - A function that passes the current tick value and expects a nicely formatted value in return. */
+	export let formatTick = (d) => d;
+
+	/** @type {Boolean} [snapTicks=true] - Instead of centering the text on the first and the last items, align them to the edges of the chart. */
+	export let snapTicks = true;
+
+	/** @type {string} [tickSide='bottom'] - Position of tick labels. Can be 'top' or 'bottom' */
+	export let tickSide = `bottom`;
+
+	/** @type {Number} [steps=100] - Number of samples to take of the color ramp to create the linear gradient */
+	export let steps = 100;
+
+	$: tickVals = Array.isArray(ticks)
+		? ticks
+		: typeof ticks === 'function'
+		? ticks($zScale.ticks())
+		: $zScale.ticks(ticks);
+
+	$: ramped = [...Array(steps).keys()].map((i) => $zScale(i / steps));
+
+	$: labelFlexDir = {
+		left: `row`,
+		right: `row-reverse`,
+		'top-left': `column`,
+		'top-right': `column`,
+		'bottom-left': `column-reverse`,
+		'bottom-right': `column-reverse`
+	}[labelSide];
+
+	$: tickFlexDir = {
+		top: `column-reverse`,
+		bottom: `column`
+	}[tickSide];
+
+	$: tickPos = tickMarks
+		? {
+				bottom: `top: 4px`,
+				top: `bottom: 4px`
+		  }[tickSide]
+		: {
+				bottom: `top: 0`,
+				top: `bottom: 0`
+		  }[tickSide];
+
+	$: tickPosMark = {
+		bottom: `top: 0`,
+		top: `bottom: 0`
+	}[tickSide];
+</script>
+
+<div style:flex-direction={labelFlexDir} class="colorbar" class:snapTicks class:tickMarks>
+	{#if label}<span class="cbar-label" data-labelside={labelSide} data-tickside={tickSide}
+			>{label}</span
+		>{/if}
+	<div
+		class="bar-container"
+		style:flex={labelSide === 'left' || labelSide === 'right' ? '1' : null}
+		style:flex-direction={tickFlexDir}
+	>
+		<div class="gradient-bar" style:background="linear-gradient(to right, {ramped})" />
+		<div class="tick-container">
+			{#each tickVals as tick_label, i}
+				{#if tickMarks === true}
+					<div
+						class="tick-mark"
+						style="left: calc(100% * {i} / {tickVals?.length - 1});{tickPosMark}; {i ===
+						tickVals?.length - 1
+							? 'transform: translateX(-1px)'
+							: i
+							? 'transform: translateX(-0.5px)'
+							: ''}"
+					/>
+				{/if}
+				<span
+					class="tick tick-{i}"
+					style="left: calc(100% * {i} / {tickVals?.length - 1}); {tickPos}"
+				>
+					{formatTick(tick_label)}
+				</span>
+			{/each}
+		</div>
+	</div>
+</div>
+
+<style>
+	div.colorbar {
+		display: flex;
+		box-sizing: border-box;
+		align-items: baseline;
+		position: relative;
+		margin: var(--cbar-margin);
+		padding: var(--cbar-padding);
+		font-size: var(--cbar-font-size, 12px);
+		width: var(--cbar-width);
+	}
+	div.colorbar > div {
+		position: relative;
+		width: 100%;
+		height: var(--cbar-height, 2em);
+		border-radius: var(--cbar-border-radius, 0);
+	}
+	.tick-container > span {
+		position: absolute;
+		transform: translate(-50%);
+		font-weight: var(--cbar-tick-label-font-weight, lighter);
+		font-size: var(--cbar-tick-label-font-size, --cbar-font-size);
+		color: var(--cbar-tick-label-color);
+		background: var(--cbar-tick-label-bg);
+	}
+	.bar-container,
+	.tick-container {
+		display: flex;
+	}
+	.tick-container {
+		position: relative;
+	}
+	.gradient-bar,
+	.tick-container {
+		flex: 1;
+	}
+
+	.cbar-label[data-labelside='right'][data-tickside='top'],
+	.cbar-label[data-labelside='left'][data-tickside='top'] {
+		transform: translateY(4px);
+		align-self: end;
+	}
+	.cbar-label[data-labelside='right'][data-tickside='bottom'],
+	.cbar-label[data-labelside='left'][data-tickside='bottom'] {
+		transform: translateY(-1px);
+	}
+	.cbar-label[data-labelside*='top-'] {
+		padding-bottom: 2px;
+	}
+	.cbar-label[data-labelside*='bottom-'] {
+		padding-top: 2px;
+	}
+	.cbar-label[data-labelside*='bottom-'][data-tickside='bottom'] {
+		padding-top: 5px;
+	}
+	.cbar-label[data-labelside*='top-'][data-tickside='top'] {
+		padding-bottom: 5px;
+	}
+	.cbar-label[data-labelside*='-right'] {
+		align-self: flex-end;
+	}
+	.cbar-label[data-labelside*='-left'] {
+		align-self: flex-start;
+	}
+	.cbar-label[data-labelside='left'] {
+		padding-right: 4px;
+	}
+	.cbar-label[data-labelside='right'] {
+		padding-left: 4px;
+	}
+
+	.colorbar.snapTicks .tick:last-child {
+		transform: translateX(-100%);
+	}
+	.colorbar.snapTicks .tick.tick-0 {
+		transform: translateX(0);
+	}
+	.tick-mark {
+		position: absolute;
+		border-left: 1px solid #aaa;
+		--length: 6px;
+		height: var(--length);
+		bottom: calc(-1 * var(--length));
+	}
+</style>

src/routes/_components.js

@@ -19,6 +19,7 @@ import CirclePack from './_components/CirclePack.svelte';
 import CirclePackForce from './_components/CirclePackForce.svelte';
 import ClevelandDotPlot from './_components/ClevelandDotPlot.svelte';
 import ClevelandDotPlotHtml from './_components/ClevelandDotPlot.html.svelte';
+import ColorBar from './_components_ssr/ColorBar.html.svelte';
 import Column from './_components/Column.svelte';
 import ColumnStacked from './_components/ColumnStacked.svelte';
 import Line from './_components/Line.svelte';
@@ -115,5 +116,6 @@ export default [
 			{ slug: 'Key.html.svelte', component: Key },
 			{ slug: 'Labels.html.svelte', component: Labels },
 			{ slug: 'GroupLabels.html.svelte', component: GroupLabels },
+			{ slug: 'ColorBar.html.svelte', component: ColorBar },
 		] }
 ];

src/routes/_components_ssr/ColorBar.html.svelte

@@ -0,0 +1,125 @@
+<script>
+	import { LayerCake, Html } from 'layercake';
+	import { scaleSequential, scaleDiverging } from 'd3-scale';
+	import * as d3ScaleChromatic from 'd3-scale-chromatic';
+
+	import ColorBar from '../../_components/ColorBar.html.svelte';
+
+	const data = [
+		{ myZ: -1 },
+		{ myZ: 0.25 },
+		{ myZ: 0.5 },
+		{ myZ: 0.75 },
+		{ myZ: 1 }
+	];
+
+	const colorScales = Object.fromEntries(Object.entries(d3ScaleChromatic).map(([k, v]) => {
+		if (k.startsWith('interpolate')) {
+			return [k, v];
+		}
+		return null;
+	}).filter(Boolean));
+
+	const zKey = 'myZ';
+	let cbarWidth = 100;
+	// let cbarHeight = 1;
+	let nTicks = 3;
+	let snapTicks = true;
+	let tickMarks = true;
+	let tickSide = 'bottom';
+	let labelSide = 'left';
+	let scaleName = 'interpolateRdBu';
+</script>
+
+<div class="chart-container">
+	<LayerCake
+		ssr={true}
+		z={zKey}
+		zScale={scaleDiverging().interpolator(colorScales[scaleName])}
+		{data}
+		zDomain={[-1, 0, 1]}
+		debug
+	>
+		<Html>
+			<ColorBar label="Label one" {labelSide} formatTick={d => d * 100} {tickSide} {snapTicks} {tickMarks} ticks={nTicks} --cbar-width="{cbarWidth}%" />
+		</Html>
+	</LayerCake>
+</div>
+
+<div class="controls-container">
+		<div class="row">
+			<label class="form-label" for="cbar-width">width:</label>
+			<input type="range" bind:value={cbarWidth} min="50" max="100" /> <span style="display:inline-block;width:25px;text-align:right;">{cbarWidth}%</span>
+		</div>
+		<!-- <div class="row">
+			<label class="form-label" for="n-ticks">ticks:</label>
+			<input type="range" bind:value={nTicks} min="1" max="10" /> {nTicks}
+		</div> -->
+
+		<div class="row">
+			<label class="form-label" for="snap-ticks">snap ticks</label>
+			<input id="snap-ticks" type="checkbox" bind:checked={snapTicks} />
+		</div>
+	<div class="row">
+		<label class="form-label" for="tick-marks">tick marks</label>
+		<input id="tick-marks" type="checkbox" bind:checked={tickMarks} />
+	</div>
+
+	<div class="row">
+		<div class="form-label">tick side:</div>
+		<select bind:value={tickSide}>
+			<option value="top">top</option>
+			<option value="bottom">bottom</option>
+		</select>
+	</div>
+
+	<div class="row">
+		<div class="form-label">label side:</div>
+		<select bind:value={labelSide}>
+			<option value="top-left">top-left</option>
+			<option value="top-right">top-right</option>
+			<option value="right">right</option>
+			<option value="bottom-left">bottom-left</option>
+			<option value="bottom-right">bottom-right</option>
+			<option value="left">left</option>
+		</select>
+	</div>
+	<div class="row">
+		<div class="form-label">scale:</div>
+		<select bind:value={scaleName}>
+			{#each Object.keys(colorScales) as n}
+				<option value={n}>{n}</option>
+			{/each}
+		</select>
+	</div>
+</div>
+
+
+<style>
+	/*
+		The wrapper div needs to have an explicit width and height in CSS.
+		It can also be a flexbox child or CSS grid element.
+		The point being it needs dimensions since the <LayerCake> element will
+		expand to fill it.
+	*/
+	.chart-container {
+		width: 100%;
+		height: 50px;
+		margin-top: 5px;
+	}
+	.controls-container {
+		margin-bottom: 21px;
+		max-width: 325px;
+		text-align: right;
+	}
+	.row {
+		display: flex;
+		justify-content: space-between;
+		margin-bottom: 2px;
+		font-size: 0.8em;
+		font-family: Consolas, monaco, monospace;
+	}
+	.row input[type="range"]{
+		height: 15px;
+	}
+</style>

src/routes/_components_ssr/Key.html.svelte

@@ -43,6 +43,7 @@
 
 <div class="chart-container">
 	<LayerCake
+		ssr={true}
 		padding={{ top: 10 }}
 		x={xKey}
 		y={yKey}