Add CSS-animation based typing animation
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0801e85839
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GPG Key ID:
49670FD774E43268
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<extends src="./lib/html/base.html">
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<block name="stylesheets">
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<style>
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.no-js .head-line .typed {
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visibility: visible;
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}
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.head-line .typed {
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visibility: hidden;
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}
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</style>
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</block>
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<block name="content">
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<h1 class="title head-line has-text-weight-normal is-family-monospace">
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$ <span class="typed">Welcome to tlater.net!</span>
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$ <span id="typed-welcome"></span>
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</h1>
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<hr />
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119
src/index.ts
119
src/index.ts
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import jQuery from "jquery";
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// Helpers
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/**
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* "Types" out a DOM element, emulating the way a human might.
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*/
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class Typer {
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private element: JQuery;
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private text: string;
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private cursor: boolean;
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private typed: number;
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private min: number;
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private max: number;
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private blink_tick: number;
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private blink_timeout: number;
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private end?: number;
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/**
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* Create the typer.
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* @param {HTMLElement} element - The element to type.
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* @param {number} blink - The time between cursor blinks.
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* @param {number} blink_timeout - How long the cursor should keep
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* blinking for after the text
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* finishes typing.
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*/
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constructor(element: JQuery<HTMLElement>, blink: number, blink_timeout: number) {
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// Retrieve the current content and wipe it. We also make the
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// element visible if it was hidden.
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this.element = element;
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this.text = this.element.html();
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this.element.html("");
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this.element.css("visibility", "visible");
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this.cursor = false;
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this.typed = 0;
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this.min = 20;
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this.max = 70;
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this.blink_tick = blink;
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this.blink_timeout = blink_timeout;
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this.end = null;
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}
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/**
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* Start typing.
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*/
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type() {
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this._type();
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this._blink();
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}
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/**
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* Draw the current text line, i.e., anything that has been typed
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* so far, and a cursor if it is currently supposed to be on.
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* @private
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*/
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_draw() {
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let text = this.text.slice(0, this.typed);
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if (this.cursor) {
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text += "\u2588";
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}
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window.requestAnimationFrame(() => this.element.html(text));
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}
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/**
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* Type the next character, and prepare to draw the next one. If
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* no new characters are to be drawn, set the end timestamp.
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* @private
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*/
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_type() {
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this.typed += 1;
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this._draw();
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if (this.typed != this.text.length)
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setTimeout(this._type.bind(this), this._type_tick());
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else {
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this.end = Date.now();
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}
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}
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/**
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* Make the cursor change blink status, and prepare for the next
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* blink.
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* @private
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*/
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_blink() {
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this.cursor = !this.cursor;
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this._draw();
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// As long as we are typing, keep blinking
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if (this.typed != this.text.length)
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setTimeout(this._blink.bind(this), this.blink_tick);
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// Once typing ends, keep going for a little bit
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else if (Date.now() - this.end < this.blink_timeout)
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setTimeout(this._blink.bind(this), this.blink_tick);
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// Make sure we get rid of the cursor in the end
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else {
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this.cursor = true;
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setTimeout(this._blink.bind(this), this.blink_tick);
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}
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}
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/**
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* Calculate a "human" time for the next character to type.
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* @private
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*/
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_type_tick() {
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return Math.round(Math.random() * this.max) + this.min;
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}
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}
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jQuery(($) => {
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const typer = new Typer($(".head-line .typed").first(), 500, 3000);
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typer.type();
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});
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import jQuery from "jquery";
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jQuery(($) => $("html").removeClass("no-js"));
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@ -0,0 +1,130 @@
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@use "sass:math";
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@use "sass:list";
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/// Animate a blinking cursor.
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@mixin cursor($duration) {
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$name: cursor-09d03260130069771b6ddc1cb415f39fdd27ddfab7b01ba91273398c2d245ae4;
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// The number of times we need to blink is = the number of full
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// seconds (500ms * 2) that fit in the total duration, rounded up,
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// and doubled.
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$iterations: math.ceil(math.div($duration, 1s)) * 2;
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animation: $name ease-in-out 500ms $iterations alternate;
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content: " ";
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@keyframes #{$name} {
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from {
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content: " ";
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}
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to {
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content: "█";
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}
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}
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}
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/// Animate a piece of text as if it was being typed by a human.
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@mixin typed($text, $duration) {
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// We don't want a linearly typed set of text, which makes this
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// singificantly more complex.
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//
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// CSS animations normally do not permit per-frame changes in
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// duration (since the total animation time is fixed). This means we
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// need to create multiple animations, and delay them so that they
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// happen in the time sequence we want.
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//
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// We generate the raw values with _generate-animations, and then
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// split up the result into the animation API.
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$frames: str-length($text);
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$animations: _generate-animations($frames, 1.2s);
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animation-name: _unzip($animations, 1);
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animation-delay: _unzip($animations, 3);
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animation-fill-mode: forwards;
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content: "";
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// We need to type each character in separate animations, see above
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// comment.
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@each $name, $character in $animations {
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@keyframes #{$name} {
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from {
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content: str-slice($text, 0, $character);
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}
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to {
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content: str-slice($text, 0, $character + 1);
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}
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}
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}
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}
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/// Unzip a nested set of lists, taking the nth value of each sublist.
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@function _unzip($lists, $i) {
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$out: ();
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$sep: comma;
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@each $sublist in $lists {
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$out: list.append($out, list.nth($sublist, $i), $sep);
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}
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@return $out;
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}
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/// Compute the sum of all numbers in a list.
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@function _sum($list) {
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$out: 0;
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@each $val in $list {
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$out: $out + $val;
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}
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@return $out;
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}
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/// Produce a list from a shorter list by repeating it up until size
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/// $length.
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@function _round-robin($base, $length) {
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$out: ();
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$sep: list.separator($out);
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@for $i from 0 through $length {
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$out: list.append($out, list.nth($base, $i % list.length($base) + 1));
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}
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@return $out;
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}
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/// Generate the actual animation values.
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///
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/// This generates a nested list as:
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///
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/// (keyframe-name, index, start time)
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///
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/// The duration of each frame is taken from the internal $delays in a
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/// round robin fashion, to give some amount of human-like variance to
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/// the duration of each frame.
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///
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/// Start time is set to the time at which the frame should start to
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/// achieve the desired frame-by-frame duration.
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@function _generate-animations($number, $total_duration) {
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$id: d66fa0449c0b4d4ca287f8c96428af928b2987b4d88b72b7d60152d9a55d9f29;
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$out: ();
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$sep: list.separator($out);
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// A set of "human-like" delays for each typed character. In
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// practice, my typing seems to be about 20-70ms, but it looks a bit
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// nicer to increase all typing by 20ms to make the effect more
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// noticeable.
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//
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// Numbers generated once with a random number generator, rather
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// than using `math.random()`, since they end up in CSS verbatim,
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// and the build would be non-reproducible if we didn't do it this
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// way. Using `math.random() wouldn't change this dynamically each
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// time the page loads anyway, so we don't really lose anything by
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// pre-generating these numbers.
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$delays: 69ms, 83ms, 49ms, 48ms, 52ms, 59ms, 40ms, 71ms, 80ms, 67ms;
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@for $animation from 0 through $number {
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$out: list.append($out, (
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type-#{$id}-#{$animation},
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$animation,
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_sum(_round_robin($delays, $animation))
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), $sep);
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}
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@return $out;
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}
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@ -1,6 +1,17 @@
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@import "./_custom-bulma";
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@import "./_typed";
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html, body {
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height: 100%;
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width: 100%;
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}
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#typed-welcome {
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&::before {
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@include typed("Welcome to tlater.net!", 1.2s);
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}
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&::after {
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@include cursor(6s);
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}
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}
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