ssvg.js

/*******************************************************************************
MIT License

Copyright (c) 2019 Juan Patten

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/**
 * Simple SVG
 *
 * A wrapper around the built-in `SVGElement` which adds some creature
 * comforts that make creating SVGs a lot less verbose.
 *
 * Idea
 * --------------------
 * SVG is really not that hard to understand, and in fact it's pretty
 * pleasant to work with, conceptually. In practice, however, it
 * involves a ton of very verbose method calls with arcane namespace
 * strings, and some other annoyances.
 *
 * By minimizing that boilerplate, we can bring practice closer to
 * concept and provide a pretty decent way of creating SVGs.
 *
 *
 * Usage
 * --------------------
 * To start, create an instance:
 * 	
 * 	let svg = new SSVG()
 *
 * All of the `SVGElement` types can be created and immediately appended
 * to the `SVGElement` by calling their name as a method:
 *
 * 	svg.circle()  // appends & returns a new <circle> (SVGCircleElement)
 * 	svg.line()    // appends & returns a new <line> (SVGLineElement)
 * 	// etc...
 *
 * To just create an element without appending, use the `create*` variation:
 *
 * 	svg.createCircle()  // returns a new <circle>
 * 	svg.createLine()    // returns a new <line>
 *	// etc...
 *
 * Created elements also have some syntax sugar applied. Normally, the
 * short syntax (`circle.cx = 10`) doesn't work because those properties
 * are read-only. Instead you have to do `circle.setAttribute('cx', 10)`
 *
 * SSVG makes those attributes writable:
 *
 * 	let circle = svg.circle()
 * 	circle.cx = 100
 * 	circle.cy = 100
 * 	circle.r = 50
 * 	circle.fill = 'red'
 * 	circle.stroke = 'blue'
 * 	// etc...
 *
 * You can also set attributes when you create the element:
 *
 * 	let circle = svg.circle({ 
 * 		cx: 100, 
 * 		cy: 100, 
 * 		r: 50,
 * 		fill: 'red',
 * 		stroke: 'blue',
 * 		// etc...
 * 	})
 *
 * Elements can also create/append nested children. This only makes
 * sense to do with the `g` (group) element:
 *
 * 	let g = svg.g({fill: red})
 * 	g.circle({cx:100, cy:100, r:50})
 * 	g.rect({x:10, y:10, width:50, height:50})
 *
 * You can apply classes to elements, but use `.class` instead of `.className`:
 *
 * 	let circle = svg.circle(...)
 * 	circle.class = 'myClass'
 *
 * The actual Element instance can be gotten from the `.root` property:
 *	
 *	svg.root      // SVGElement
 *	circle.root   // SVGCircleElement
 *
 *
 * Documentation:
 * 	SVG: https://developer.mozilla.org/en-US/docs/Web/SVG/Element
 *	Proxy: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
 */


const svgns = 'http://www.w3.org/2000/svg'


const SSVGProxyHandler = {
	get: function(instance, propName) {
		// Figure out what element we're creating (if any)
		let [_, isCreate, elemName] = propName.match(/(create)?(\w+)/)
		let upperElemName = elemName[0].toUpperCase() + elemName.slice(1)
		let className = `SVG${upperElemName}Element`
		let validElement = window.hasOwnProperty(className)
		elemName = elemName.toLowerCase()

		// If not a valid svg element, fall back to the instance
		if (! validElement) {
			let prop = instance[propName]
			if (typeof prop == 'function') {
				return prop.bind(instance)
			} else {
				return prop
			}
		}

		// Otherwise, return the creator function
		return function(attrs = {}) {
			let elem = document.createElementNS(svgns, elemName)
			for (let [attrName, attrVal] of Object.entries(attrs)) {
				elem.setAttribute(attrName, attrVal)
			}

			if (! isCreate) {
				instance.root.append(elem)
			}

			return new SSVGElementProxy(elem)
		}
	},

	set: function(instance, propName, val) {
		let desc = Object.getOwnPropertyDescriptor(instance, propName)
		if (desc && desc.writable) { // if this is a writable property, just set it
			instance[propName] = val
		} else { // otherwise, assume it's an attribute
			instance.setAttribute(propName, val)
		}
	},
}



class SSVGProxy {
	constructor(ssvg) {
		return new Proxy(ssvg, SSVGProxyHandler)
	}
}


class SSVGElementProxy {
	constructor(element) {
		let proxy = new Proxy(element, SSVGProxyHandler)
		Object.defineProperty(proxy, 'root', {value: element})
		return proxy
	}
}



export default class SSVG {
	root = document.createElementNS(svgns, 'svg')

	constructor(attrs = {}) {
		for (let [attrName, attrVal] of Object.entries(attrs)) {
			this.root.setAttribute(attrName, attrVal)
		}

		return new SSVGProxy(this)
	}
}