flix/docs/zoom.js

/* https://github.com/spinningarrow/zoom-vanilla.js

The MIT License

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/

+function () { "use strict";
	var OFFSET = 80

	// From http://youmightnotneedjquery.com/#offset
	function offset(element) {
		var rect = element.getBoundingClientRect()
		var scrollTop = window.pageYOffset ||
			document.documentElement.scrollTop ||
			document.body.scrollTop ||
			0
		var scrollLeft = window.pageXOffset ||
			document.documentElement.scrollLeft ||
			document.body.scrollLeft ||
			0
		return {
			top: rect.top + scrollTop,
			left: rect.left + scrollLeft
		}
	}

	function zoomListener() {
		var activeZoom = null
		var initialScrollPosition = null
		var initialTouchPosition = null

		function listen() {
			document.body.addEventListener('click', function (event) {
				if (event.target.getAttribute('data-action') !== 'zoom' ||
					event.target.tagName !== 'IMG') return

				zoom(event)
			})
		}

		function zoom(event) {
			event.stopPropagation()

			if (document.body.classList.contains('zoom-overlay-open')) return

			if (event.metaKey || event.ctrlKey) return openInNewWindow()

			closeActiveZoom({ forceDispose: true })

			activeZoom = vanillaZoom(event.target)
			activeZoom.zoomImage()

			addCloseActiveZoomListeners()
		}

		function openInNewWindow() {
			window.open(event.target.getAttribute('data-original') ||
				event.target.currentSrc ||
				event.target.src,
				'_blank')
		}

		function closeActiveZoom(options) {
			options = options || { forceDispose: false }
			if (!activeZoom) return

			activeZoom[options.forceDispose ? 'dispose' : 'close']()
			removeCloseActiveZoomListeners()
			activeZoom = null
		}

		function addCloseActiveZoomListeners() {
			// todo(fat): probably worth throttling this
			window.addEventListener('scroll', handleScroll)
			document.addEventListener('click', handleClick)
			document.addEventListener('keyup', handleEscPressed)
			document.addEventListener('touchstart', handleTouchStart)
			document.addEventListener('touchend', handleClick)
		}

		function removeCloseActiveZoomListeners() {
			window.removeEventListener('scroll', handleScroll)
			document.removeEventListener('keyup', handleEscPressed)
			document.removeEventListener('click', handleClick)
			document.removeEventListener('touchstart', handleTouchStart)
			document.removeEventListener('touchend', handleClick)
		}

		function handleScroll(event) {
			if (initialScrollPosition === null) initialScrollPosition = window.pageYOffset
			var deltaY = initialScrollPosition - window.pageYOffset
			if (Math.abs(deltaY) >= 40) closeActiveZoom()
		}

		function handleEscPressed(event) {
			if (event.keyCode == 27) closeActiveZoom()
		}

		function handleClick(event) {
			event.stopPropagation()
			event.preventDefault()
			closeActiveZoom()
		}

		function handleTouchStart(event) {
			initialTouchPosition = event.touches[0].pageY
			event.target.addEventListener('touchmove', handleTouchMove)
		}

		function handleTouchMove(event) {
			if (Math.abs(event.touches[0].pageY - initialTouchPosition) <= 10) return
			closeActiveZoom()
			event.target.removeEventListener('touchmove', handleTouchMove)
		}

		return { listen: listen }
	}

	var vanillaZoom = (function () {
		var fullHeight = null
		var fullWidth = null
		var overlay = null
		var imgScaleFactor = null

		var targetImage = null
		var targetImageWrap = null
		var targetImageClone = null

		function zoomImage() {
			var img = document.createElement('img')
			img.onload = function () {
				fullHeight = Number(img.height)
				fullWidth = Number(img.width)
				zoomOriginal()
			}
			img.src = targetImage.currentSrc || targetImage.src
		}

		function zoomOriginal() {
			targetImageWrap = document.createElement('div')
			targetImageWrap.className = 'zoom-img-wrap'
			targetImageWrap.style.position = 'absolute'
			targetImageWrap.style.top = offset(targetImage).top + 'px'
			targetImageWrap.style.left = offset(targetImage).left + 'px'

			targetImageClone = targetImage.cloneNode()
			targetImageClone.style.visibility = 'hidden'

			targetImage.style.width = targetImage.offsetWidth + 'px'
			targetImage.parentNode.replaceChild(targetImageClone, targetImage)

			document.body.appendChild(targetImageWrap)
			targetImageWrap.appendChild(targetImage)

			targetImage.classList.add('zoom-img')
			targetImage.setAttribute('data-action', 'zoom-out')

			overlay = document.createElement('div')
			overlay.className = 'zoom-overlay'

			document.body.appendChild(overlay)

			calculateZoom()
			triggerAnimation()
		}

		function calculateZoom() {
			targetImage.offsetWidth // repaint before animating

			var originalFullImageWidth  = fullWidth
			var originalFullImageHeight = fullHeight

			var maxScaleFactor = originalFullImageWidth / targetImage.width

			var viewportHeight = window.innerHeight - OFFSET
			var viewportWidth  = window.innerWidth - OFFSET

			var imageAspectRatio    = originalFullImageWidth / originalFullImageHeight
			var viewportAspectRatio = viewportWidth / viewportHeight

			if (originalFullImageWidth < viewportWidth && originalFullImageHeight < viewportHeight) {
				imgScaleFactor = maxScaleFactor
			} else if (imageAspectRatio < viewportAspectRatio) {
				imgScaleFactor = (viewportHeight / originalFullImageHeight) * maxScaleFactor
			} else {
				imgScaleFactor = (viewportWidth / originalFullImageWidth) * maxScaleFactor
			}
		}

		function triggerAnimation() {
			targetImage.offsetWidth // repaint before animating

			var imageOffset = offset(targetImage)
			var scrollTop   = window.pageYOffset

			var viewportY = scrollTop + (window.innerHeight / 2)
			var viewportX = (window.innerWidth / 2)

			var imageCenterY = imageOffset.top + (targetImage.height / 2)
			var imageCenterX = imageOffset.left + (targetImage.width / 2)

			var translateY = Math.round(viewportY - imageCenterY)
			var translateX = Math.round(viewportX - imageCenterX)

			var targetImageTransform = 'scale(' + imgScaleFactor + ')'
			var targetImageWrapTransform =
				'translate(' + translateX + 'px, ' + translateY + 'px) translateZ(0)'

			targetImage.style.webkitTransform = targetImageTransform
			targetImage.style.msTransform = targetImageTransform
			targetImage.style.transform = targetImageTransform

			targetImageWrap.style.webkitTransform = targetImageWrapTransform
			targetImageWrap.style.msTransform = targetImageWrapTransform
			targetImageWrap.style.transform = targetImageWrapTransform

			document.body.classList.add('zoom-overlay-open')
		}

		function close() {
			document.body.classList.remove('zoom-overlay-open')
			document.body.classList.add('zoom-overlay-transitioning')

			targetImage.style.webkitTransform = ''
			targetImage.style.msTransform = ''
			targetImage.style.transform = ''

			targetImageWrap.style.webkitTransform = ''
			targetImageWrap.style.msTransform = ''
			targetImageWrap.style.transform = ''

			if (!'transition' in document.body.style) return dispose()

			targetImageWrap.addEventListener('transitionend', dispose)
			targetImageWrap.addEventListener('webkitTransitionEnd', dispose)
		}

		function dispose() {
			targetImage.removeEventListener('transitionend', dispose)
			targetImage.removeEventListener('webkitTransitionEnd', dispose)

			if (!targetImageWrap || !targetImageWrap.parentNode) return

			targetImage.classList.remove('zoom-img')
			targetImage.style.width = ''
			targetImage.setAttribute('data-action', 'zoom')

			targetImageClone.parentNode.replaceChild(targetImage, targetImageClone)
			targetImageWrap.parentNode.removeChild(targetImageWrap)
			overlay.parentNode.removeChild(overlay)

			document.body.classList.remove('zoom-overlay-transitioning')
		}

		return function (target) {
			targetImage = target
			return { zoomImage: zoomImage, close: close, dispose: dispose }
		}
	}())

	zoomListener().listen()
}()