width and height bindings

src/compile/nodes/Binding.ts

@@ -6,6 +6,7 @@ import flattenReference from '../../utils/flattenReference';
 import Compiler from '../Compiler';
 import Block from '../dom/Block';
 import Expression from './shared/Expression';
+import { dimensions } from '../../utils/patterns';
 
 const readOnlyMediaAttributes = new Set([
 	'duration',
@@ -14,6 +15,9 @@ const readOnlyMediaAttributes = new Set([
 	'played'
 ]);
 
+// TODO a lot of this element-specific stuff should live in Element —
+// Binding should ideally be agnostic between Element and Component
+
 export default class Binding extends Node {
 	name: string;
 	value: Expression;
@@ -57,7 +61,10 @@ export default class Binding extends Node {
 		const node: Element = this.parent;
 
 		const needsLock = node.name !== 'input' || !/radio|checkbox|range|color/.test(node.getStaticAttributeValue('type'));
-		const isReadOnly = node.isMediaNode() && readOnlyMediaAttributes.has(this.name);
+		const isReadOnly = (
+			(node.isMediaNode() && readOnlyMediaAttributes.has(this.name)) ||
+			dimensions.test(this.name)
+		);
 
 		let updateCondition: string;
 
@@ -103,8 +110,7 @@ export default class Binding extends Node {
 		if (this.name === 'currentTime' || this.name === 'volume') {
 			updateCondition = `!isNaN(${snippet})`;
 
-			if (this.name === 'currentTime')
-				initialUpdate = null;
+			if (this.name === 'currentTime') initialUpdate = null;
 		}
 
 		if (this.name === 'paused') {
@@ -117,6 +123,12 @@ export default class Binding extends Node {
 			initialUpdate = null;
 		}
 
+		// bind:offsetWidth and bind:offsetHeight
+		if (dimensions.test(this.name)) {
+			initialUpdate = null;
+			updateDom = null;
+		}
+
 		return {
 			name: this.name,
 			object: name,

src/compile/nodes/Element.ts

@@ -17,6 +17,7 @@ import Action from './Action';
 import Text from './Text';
 import * as namespaces from '../../utils/namespaces';
 import mapChildren from './shared/mapChildren';
+import { dimensions } from '../../utils/patterns';
 
 // source: https://gist.github.com/ArjanSchouten/0b8574a6ad7f5065a5e7
 const booleanAttributes = new Set('async autocomplete autofocus autoplay border challenge checked compact contenteditable controls default defer disabled formnovalidate frameborder hidden indeterminate ismap loop multiple muted nohref noresize noshade novalidate nowrap open readonly required reversed scoped scrolling seamless selected sortable spellcheck translate'.split(' '));
@@ -262,7 +263,7 @@ export default class Element extends Node {
 			parentNode;
 
 		block.addVariable(name);
-		const renderStatement = getRenderStatement(this.compiler, this.namespace, this.name);
+		const renderStatement = getRenderStatement(this.namespace, this.name);
 		block.builders.create.addLine(
 			`${name} = ${renderStatement};`
 		);
@@ -489,13 +490,27 @@ export default class Element extends Node {
 			`);
 
 			group.events.forEach(name => {
-				block.builders.hydrate.addLine(
-					`@addListener(${this.var}, "${name}", ${handler});`
-				);
+				if (name === 'resize') {
+					// special case
+					const resize_listener = block.getUniqueName(`${this.var}_resize_listener`);
+					block.addVariable(resize_listener);
 
-				block.builders.destroy.addLine(
-					`@removeListener(${this.var}, "${name}", ${handler});`
-				);
+					block.builders.mount.addLine(
+						`${resize_listener} = @addResizeListener(${this.var}, ${handler});`
+					);
+
+					block.builders.unmount.addLine(
+						`${resize_listener}.cancel();`
+					);
+				} else {
+					block.builders.hydrate.addLine(
+						`@addListener(${this.var}, "${name}", ${handler});`
+					);
+
+					block.builders.destroy.addLine(
+						`@removeListener(${this.var}, "${name}", ${handler});`
+					);
+				}
 			});
 
 			const allInitialStateIsDefined = group.bindings
@@ -509,6 +524,14 @@ export default class Element extends Node {
 					`if (!(${allInitialStateIsDefined})) #component.root._beforecreate.push(${handler});`
 				);
 			}
+
+			if (group.events[0] === 'resize') {
+				this.compiler.target.hasComplexBindings = true;
+
+				block.builders.hydrate.addLine(
+					`#component.root._beforecreate.push(${handler});`
+				);
+			}
 		});
 
 		this.initialUpdate = mungedBindings.map(binding => binding.initialUpdate).filter(Boolean).join('\n');
@@ -916,7 +939,6 @@ export default class Element extends Node {
 }
 
 function getRenderStatement(
-	compiler: Compiler,
 	namespace: string,
 	name: string
 ) {
@@ -971,6 +993,12 @@ const events = [
 			node.name === 'input' && /radio|checkbox|range/.test(node.getStaticAttributeValue('type'))
 	},
 
+	{
+		eventNames: ['resize'],
+		filter: (node: Element, name: string) =>
+			dimensions.test(name)
+	},
+
 	// media events
 	{
 		eventNames: ['timeupdate'],

src/shared/dom.js

@@ -193,3 +193,32 @@ export function selectMultipleValue(select) {
 		return option.__value;
 	});
 }
+
+export function addResizeListener(element, fn) {
+	if (getComputedStyle(element).position === 'static') {
+		element.style.position = 'relative';
+	}
+
+	const object = document.createElement('object');
+	object.setAttribute('style', 'display: block; position: absolute; top: 0; left: 0; height: 100%; width: 100%; overflow: hidden; pointer-events: none; z-index: -1;');
+	object.type = 'text/html';
+
+	object.onload = () => {
+		object.contentDocument.defaultView.addEventListener('resize', fn);
+	};
+
+	if (/Trident/.test(navigator.userAgent)) {
+		element.appendChild(object);
+		object.data = 'about:blank';
+	} else {
+		object.data = 'about:blank';
+		element.appendChild(object);
+	}
+
+	return {
+		cancel: () => {
+			object.contentDocument.defaultView.removeEventListener('resize', fn);
+			element.removeChild(object);
+		}
+	};
+}

src/utils/patterns.ts

@@ -1 +1,3 @@
 export const whitespace = /[ \t\r\n]/;
+
+export const dimensions = /^(?:offset|client)(?:Width|Height)$/;

src/validate/html/validateElement.ts

@@ -2,6 +2,8 @@ import * as namespaces from '../../utils/namespaces';
 import validateEventHandler from './validateEventHandler';
 import validate, { Validator } from '../index';
 import { Node } from '../../interfaces';
+import { dimensions } from '../../utils/patterns';
+import isVoidElementName from '../../utils/isVoidElementName';
 
 const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|tref|tspan|unknown|use|view|vkern)$/;
 
@@ -157,6 +159,23 @@ export default function validateElement(
 						message: `'${name}' binding can only be used with <audio> or <video>`
 					});
 				}
+			} else if (dimensions.test(name)) {
+				if (node.name === 'svg' && (name === 'offsetWidth' || name === 'offsetHeight')) {
+					validator.error(attribute, {
+						code: 'invalid-binding',
+						message: `'${attribute.name}' is not a valid binding on <svg>. Use '${name.replace('offset', 'client')}' instead`
+					});
+				} else if (svg.test(node.name)) {
+					validator.error(attribute, {
+						code: 'invalid-binding',
+						message: `'${attribute.name}' is not a valid binding on SVG elements`
+					});
+				} else if (isVoidElementName(node.name)) {
+					validator.error(attribute, {
+						code: 'invalid-binding',
+						message: `'${attribute.name}' is not a valid binding on void elements like <${node.name}>. Use a wrapper element instead`
+					});
+				}
 			} else {
 				validator.error(attribute, {
 					code: `invalid-binding`,