keyframe 1.1.1

A simple library for animation in Rust
Documentation 
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<!-- Preview for easing functions in docs.rs -->

<style>
	.function-preview {
		position: relative;
		display: inline-block;

		width: 260px;
		height: 110px;

		margin: 30px 40px 50px 20px;

		/* Workaround for rustdoc overriding overflow-x */
		overflow: initial !important;
	}

	.function-preview-ball {
		width: 10px;
		height: 10px;
		background-color: #F44336;
		border-radius: 50%;

		position: absolute;
		right: -20px;

		/* Shift to start of graph, then compensate for line width, then for ball height */
		bottom: calc(5px - 1px - 5px);
	}

	.function-preview-x, .function-preview-y, .function-preview-title {
		user-select: none;

		position: absolute;
		margin: 0px;

		text-align: center;
		vertical-align: middle;

		font-family: monospace;
		font-size: 13px;
		font-weight: bold;
		font-style: italic;

		color: #F44336;
	}

	.function-preview-x {
		width: 250px;
		left: 5px;
		bottom: -25px;
	}

	.function-preview-y {
		line-height: 100px;
		height: 100px;
		left: -25px;
		top: 5px;
	}

	.function-preview-title {
		font-style: normal;
		width: auto;
		left: 0px;
		bottom: -50px;
	}
</style>

<script>
	"use strict";
	var ballsToAnimate = [];
	var lastScaleFactor = devicePixelRatio;
	var lastTick = performance.now();

	function redrawPreviews() {
		document.querySelectorAll(".function-preview").forEach(function(val) {
			console.log((val.hasChildNodes() ? "Redrawn " : "Drawn ") + "preview " + val.getAttribute("data-function"));
			var canvas = val.hasChildNodes() ? val.getElementsByTagName("canvas")[0] : document.createElement("canvas");

			canvas.style.width = "260px";
			canvas.style.height = "110px";
			canvas.width = 260 * devicePixelRatio;
			canvas.height = 110 * devicePixelRatio;

			var bounds = [5, 5, 250 + 5, 100 + 5];
			for(var i = 0; i < bounds.length; i++)
				bounds[i] = bounds[i] * devicePixelRatio;

			var easingFunction;
			eval("easingFunction = function(t) { return " + val.getAttribute("data-function") + " };");

			var ctx = canvas.getContext("2d");
			ctx.clearRect(bounds[0], bounds[1], bounds[2] - bounds[0], bounds[3] - bounds[1]);

			ctx.beginPath();
			ctx.strokeStyle = "#F44336";
			ctx.lineWidth = 2 * devicePixelRatio;

			ctx.moveTo(bounds[0], bounds[3]);
			for(var x = 0; x <= 250; x += 5) {
				var value = easingFunction(x / 250.0);
				var targetX = bounds[0] + (x * devicePixelRatio);
				var targetY = bounds[3] - (easingFunction(x / 250.0) * 100.0) * devicePixelRatio;
				var diff = Math.abs(value - easingFunction((x - 1) / 250.0));

				// Approximate discontinuous functions like Math.round(t)
				if(diff < 0.5) {
					ctx.lineTo(targetX, targetY);
				}
				else {
					ctx.moveTo(targetX, targetY);
				}
			}

			ctx.stroke();

			if(!val.hasChildNodes()) {
				val.appendChild(canvas);

				var ball = document.createElement("div");
				ball.className = "function-preview-ball";
				ball.reverse = false;
				ball.progress = 0.0;
				ball.easingFunction = easingFunction;

				ballsToAnimate[ballsToAnimate.length] = ball;

				val.appendChild(ball);

				var x = document.createElement("p");
				x.innerText = "t";
				x.className = "function-preview-x";
				val.appendChild(x);

				var y = document.createElement("p");
				y.innerText = "y(t)";
				y.className = "function-preview-y";
				val.appendChild(y);

				if(val.getAttribute("data-struct") != null) {
					var title = document.createElement("a");
					title.innerText = "ease(" + val.getAttribute("data-struct") + ", ...)";
					title.className = "function-preview-title";
					title.href = window.location.href.replace("index.html", "struct." + val.getAttribute("data-struct") + ".html");
					val.appendChild(title);
				}
			}
		});

	}

	document.addEventListener("DOMContentLoaded", redrawPreviews);
	window.addEventListener("resize", function() {
		if(devicePixelRatio != lastScaleFactor) {
			redrawPreviews();
			lastScaleFactor = devicePixelRatio;
		}
	}, true);

	function tick(now) {
		var delta = (now - lastTick) / 1000.0;
		lastTick = now;

		ballsToAnimate.forEach(function(val) {
			var oldProgress = val.progress;
			val.progress += delta * 1.5;

			if(oldProgress < 1 && val.progress >= 1) {
				val.reverse = !val.reverse;
				val.progress = 0;
			}

			var position = -102 * (val.reverse ? val.easingFunction(1 - val.progress) : val.easingFunction(val.progress));

			val.style.transform = "translateY(" + position + "px)";
		});

		window.requestAnimationFrame(tick);
	}

	window.requestAnimationFrame(tick);
</script>