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<title>Alignement vertical d'une fraction</title>
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<meta name="description" content="Aligner verticalement une fraction dans son conteneur.">
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html, body {margin: 0;padding: 0;font: 1em/1.5 Verdana,sans-serif;}
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time {float: right;margin: .5em;font-size: 0.9em;color: #888;}
main {display: block;margin: auto;max-width: 60em;}
section {position: relative;margin: 0 1em 1em;}
section > :not(h2) {margin-left: 1em;}
.cde {z-index: 100;position: sticky;top: 0;border: 1px solid #EEE;background-color: rgba(255,255,255,.8);}
button {display: inline-block;margin: .25em;padding: 0 1em;border: 1px solid #CCC;border-bottom-color: #BBB;border-radius: 0;border-radius: .25em;text-decoration: none;text-shadow: 0 1px 1px rgba(255,255,255,0.75);font: inherit;line-height: 2.5;color: #333;background-color: #E6E6E6;background-image: linear-gradient(#FFF,#FFF 25%,#E6E6E6);background-repeat: no-repeat;box-shadow: inset 0 1px 0 rgba(255,255,255,0.2) ,0 1px 2px rgba(0,0,0,0.05);transition: background-position 0.1s linear;cursor: pointer;}
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button:disabled {color: #CCC;cursor: inherit;}
code {font-family: "courier new";color: #069;background-color: #F0F8FF;}
/*-- CSS issu d'eleydet --*/
.frac {
display: inline-block;
text-align: center;
vertical-align: middle;
}
.num {
display: block;
padding: 0 7px 4px 7px;
}
.den {
display: block;
padding: 2px 7px 0 7px;
border-top: 1px solid #000;
}
/*-- CSS pour démo --*/
.rendu-brut p,
.rendu-transform p,
.rendu-center p {
display: inline-block;
margin: 1em;
padding: 0 1em;
background-color: #FDE;
}
p.frac-transform {
background-color: #EEE;
}
p.frac-center {
background-color: #DEF;
}
.frac-transform > .frac > .den {
border-top: 1px solid #00F;
}
.frac-center > .frac > .den {
border-top: 1px solid #F00;
}
</style>
</head>
<body>
<main>
<header>
<time datetime="2022-09-01">Sept. 2022</time>
<h1>Alignement vertical d'une fraction</h1>
<p>Ce que l'on cherche à faire c'est centrer verticalement la barre horizontale de la fraction principale.</p>
</header>
<p class="cde">
<button onclick="alignVerticalFraction()" title="Applique un centrage vertical global">Alignement vertical global</button>
<button onclick="demoAlignVerticalFraction()" title="Applique un centrage vertical sélectif">Alignement vertical sélectif</button>
</p>
<section class="rendu-brut">
<h2>Rendu brut</h2>
<p>y = <span class="frac"><span class="num">a</span><span class="den">b</span></span></p>
<p>y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den"><span class="frac"><span class="num">c</span><span class="den">d</span></span></span></span></p>
<p>y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den">c</span></span></p>
<p>y = <span class="frac"><span class="num">a</span><span class="den"><span class="frac"><span class="num">b</span><span class="den">c</span></span></span></span></p>
</section>
<section>
<h2>Rendu alignement verticalement</h2>
<p>La barre horizontale de la fraction principale, correspond au bord haut du dénominateur, <i>ou bas du numérateur</i>, de la première fraction.
<h3>Méthode #1</h3>
<p>On ajoute une <code>transform:translateY(+/-)</code> pour recaler la fraction suivant le cas.
<div class="rendu-transform">
<p class="frac-transform">y = <span class="frac"><span class="num">a</span><span class="den">b</span></span></p>
<p class="frac-transform">y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den"><span class="frac"><span class="num">c</span><span class="den">d</span></span></span></span></p>
<p class="frac-transform">y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den">c</span></span></p>
<p class="frac-transform">y = <span class="frac"><span class="num">a</span><span class="den"><span class="frac"><span class="num">b</span><span class="den">c</span></span></span></span></p>
</div>
<h3>Méthode #2</h3>
<p>On joue avec les <code>padding-top/bottom</code> pour recaler la fraction suivant le cas.
<div class="rendu-center">
<p class="frac-center">y = <span class="frac"><span class="num">a</span><span class="den">b</span></span></p>
<p class="frac-center">y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den"><span class="frac"><span class="num">c</span><span class="den">d</span></span></span></span></p>
<p class="frac-center">y = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den">c</span></span></p>
<p class="frac-center">y = <span class="frac"><span class="num">a</span><span class="den"><span class="frac"><span class="num">b</span><span class="den">c</span></span></span></span></p>
</div>
</section>
<section>
<h2>Remarques</h2>
<p>La méthode #2 est préférable pour préserver l'espace autour du conteneur limitant ainsi les risques de débordement/superposition.
<p>Cela fonctionne également avec des fractions égales à des fractions.
<div class="rendu-center">
<p class="frac-center">y = <span class="frac"><span class="num">a</span><span class="den">b</span></span> = <span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den">c</span></span></p>
<p class="frac-transform"><span class="frac"><span class="num"><span class="frac"><span class="num">a</span><span class="den">b</span></span></span><span class="den">c</span></span> = <span class="frac"><span class="num">a</span><span class="den"><span class="frac"><span class="num">b</span><span class="den">c</span></span></span></span></p>
</div>
</section>
<footer>
<p>Voir la <a href="https://www.developpez.net/forums/showthread.php?t=2137021">discussion sur Developpez.com</a>
</footer>
</main>
<script>
"use strict";
/**
* just for démo
*/
function demoAlignVerticalFraction() {
// option calcul avec le dénominateur
const elemFrac = document.querySelectorAll(".frac");
elemFrac.forEach((el) => {
const closest = el.parentNode.closest(".frac");
// dans ce cas c'est la première fraction
if (!closest) {
// get élément à traiter (c'est une façon de faire)
const elemDenominateur = [...el.children].filter((el) => el.classList.contains("den"))[0];
// on ne sais jamais
if (!elemDenominateur) return;
// récup. des dimensions
const parent = elemDenominateur.parentNode;
// supprime padding et transform sur parent
parent.style.paddingTop = 0;
parent.style.paddingBottom = 0;
parent.style.transform = "";
const topParent = parent.offsetTop;
const topElement = elemDenominateur.offsetTop;
const hParent = parent.offsetHeight;
// calcul décalage à faire
const axe = topElement - topParent;
const decal = axe - (hParent / 2);
// application décalage
const mode = el.closest("P")
.className.split("-")
.pop();
switch (mode) {
case "transform":
// méthode #1 via un transform
parent.style.transform = `translateY(${-decal}px)`;
break;
case "center":
// méthode #2
const prop = decal > 0 ? "paddingBottom" : "paddingTop";
parent.style[prop] = `${Math.abs(decal * 2)}px`;
break;
default:
}
}
});
}
/**
* fonction générique d'alignement vertical
*/
function alignVerticalFraction() {
// option calcul avec le dénominateur
const elemFrac = document.querySelectorAll(".frac");
elemFrac.forEach((el) => {
const closest = el.parentNode.closest(".frac");
// dans ce cas c'est la première fraction
if (!closest) {
// get élément à traiter (c'est une façon de faire)
const elemDenominateur = [...el.children].filter((el) => el.classList.contains("den"))[0];
// on ne sais jamais
if (!elemDenominateur) return;
// récup. des dimensions
const parent = elemDenominateur.parentNode;
// supprime padding et transform sur parent
parent.style.paddingTop = 0;
parent.style.paddingBottom = 0;
parent.style.transform = "";
const topParent = parent.offsetTop;
const topElement = elemDenominateur.offsetTop;
const hParent = parent.offsetHeight;
// calcul décalage à faire
const axe = topElement - topParent;
const decal = axe - (hParent / 2);
// application décalage
// si décalage positif on modifie le padding-bottom
// si décalage négatif on modifie le padding-top
const prop = decal > 0 ? "paddingBottom" : "paddingTop";
parent.style[prop] = `${Math.abs(decal * 2)}px`;
}
});
}
document.addEventListener("DOMContentLoaded", () => {
demoAlignVerticalFraction();
});
</script>
</body>
</html> |
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