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leecat.art-site/accessible-image-modals/index.html

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first
2026-05-15 09:20:43 -07:00
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="icon" type="image/x-icon" href="/favicon.ico">
<title>accessible image modals | hello hello</title>
<meta name="description" content="Lee Cattarin... on the internet!">
<link rel="alternate" href="/feed.xml" type="application/atom+xml" title="hello hello">
<meta property="og:title" content="accessible image modals | hello hello">
<meta property="og:type" content="website">
<meta property="og:description" content="Lee Cattarin... on the internet!">
<meta property="og:site_name" content="hello hello">
<meta property="og:image" content="/img/snacking-seagull.jpg">
<meta property="og:image:alt" content="Image unrelated to post. A seagull floating in the water with a starfish hanging out of eir mouth.">
<meta name="generator" content="Eleventy v3.1.2">
drone build Thu May 21 16:35:46 PDT 2026
2026-05-21 23:35:46 +00:00
<meta itemprop="ai-content-declaration:version" content="1.0.0">
<meta itemprop="ai-content-declaration:level" content="none">
first
2026-05-15 09:20:43 -07:00
<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin="">
<link href="https://fonts.googleapis.com/css2?family=Atkinson+Hyperlegible+Mono:ital,wght@0,200..800;1,200..800&family=Atkinson+Hyperlegible+Next:ital,wght@0,200..800;1,200..800&display=swap" rel="stylesheet">
<script src="https://kit.fontawesome.com/884dded219.js" crossorigin="anonymous"></script>
<style>.post-metadata {
display: flex;
flex-flow: row wrap;
justify-content: space-between;
align-items: baseline;
margin: 1.5rem 0 .5rem;
}
.post-metadata p {
font-size: .9rem;
margin: 0;
}
.post-tags {
display: flex;
flex-flow: row wrap;
gap: .5rem;
list-style: none;
margin: 0;
}
.post-tags li {
margin: 0;
}
.post-tags li a {
text-decoration: none;
color: var(--color-teal);
padding: 0 .5rem;
border-radius: 1rem;
box-shadow: .15rem .15rem var(--color-shadow);
border: .08rem solid var(--color-teal);
line-height: 2;
/* Click animation handling */
position: relative;
top: 0;
left: 0;
transition: top .1s ease-in, left .1s ease-in;
}
.post-tags li a:focus-visible {
outline: none;
background-color: var(--color-teal);
color: var(--color-bg);
}
@media (any-hover: hover) {
.post-tags li a:hover {
outline: none;
background-color: var(--color-teal);
color: var(--color-bg);
}
}
@media (forced-colors: active) {
.post-tags li a:focus-visible {
outline-offset: .08rem;
outline: .08rem solid;
}
@media (any-hover: hover) {
.post-tags li a:hover {
outline-offset: .08rem;
outline: .08rem solid;
}
}
}
/* Click animation */
.post-tags li a:active {
top: .1rem;
left: .1rem;
box-shadow: .05rem .05rem var(--color-shadow);
}
/* Adapted from PrismJS 1.30.0 Tomorrow Night theme
https://prismjs.com/download
*/
code,
pre,
code[class*=language-],
pre[class*=language-] {
font-family: var(--font-family-code);
background-color: var(--color-bg-alt);
font-size: .9em;
text-shadow: 0 1px var(--color-shadow);
-moz-tab-size: 4;
-o-tab-size: 4;
tab-size: 4;
-webkit-hyphens: none;
-moz-hyphens: none;
-ms-hyphens: none;
hyphens: none;
}
pre,
pre[class*=language-] {
margin: 1rem 0;
padding: 1rem;
line-height: 1.5;
white-space: pre-wrap;
word-break: break-word;
overflow-wrap: break-word;
border-radius: .5rem;
overflow: auto;
}
:not(pre)>code,
:not(pre)>code[class*=language-] {
padding: .2rem;
border-radius: .25rem;
white-space: normal;
}
/* Selected text */
code ::-moz-selection,
code::-moz-selection,
pre ::-moz-selection,
pre::-moz-selection,
code[class*=language-] ::-moz-selection,
code[class*=language-]::-moz-selection,
pre[class*=language-] ::-moz-selection,
pre[class*=language-]::-moz-selection,
code ::selection,
code::selection,
pre ::selection,
pre::selection,
code[class*=language-] ::selection,
code[class*=language-]::selection,
pre[class*=language-] ::selection,
pre[class*=language-]::selection {
text-shadow: none;
background-color: var(--color-bg);
}
/* Syntax highlighting */
.token.namespace {
opacity: .7;
}
.token.bold,
.token.important {
font-weight:700
}
.token.italic {
font-style:italic
}
.token.block-comment,
.token.cdata,
.token.comment,
.token.doctype,
.token.prolog,
.token.punctuation {
color: var(--color-grey);
}
.token.attr-name,
.token.deleted,
.token.namespace,
.token.tag {
color: var(--color-red);
}
.token.boolean,
.token.function,
.token.number {
color: var(--color-orange);
}
.token.class-name,
.token.constant,
.token.property,
.token.symbol {
color: var(--color-yellow);
}
.token.attr-value,
.token.char,
.token.regex,
.token.string,
.token.variable,
.token.inserted {
color: var(--color-green);
}
.token.entity,
.token.operator,
.token.url,
.token.function-name {
color:var(--color-blue);
}
.token.atrule,
.token.builtin,
.token.important,
.token.keyword,
.token.selector {
color: var(--color-purple);
}
#postlist,
#taglist {
list-style: none;
}
#postlist, .post,
#taglist, .tag {
margin: 0;
}
/* Odd-numbered posts & tag layout/coloration */
.post:nth-child(odd) .postlink,
.tag:nth-child(odd) .taglink {
grid-template-areas:
'img h2'
'img info'
'img .';
grid-template-columns: 45% auto;;
--color-primary: var(--color-teal);
--color-accent: var(--color-pink);
}
/* Even-numbered posts & tags layout/coloration */
.post:nth-child(even) .postlink,
.tag:nth-child(even) .taglink {
grid-template-areas:
'h2 img'
'info img'
'. img';
grid-template-columns: auto 45%;
--color-primary: var(--color-pink);
--color-accent: var(--color-teal);
}
/* Layout for all posts on mobile */
@media (max-width: 650px) {
.post:nth-child(n) .postlink,
.tag:nth-child(n) .taglink {
grid-template-areas:
'img'
'h2'
'info';
grid-template-columns: auto;
}
}
/* Link */
.postlink,
.taglink {
display: grid;
border: .25rem solid var(--color-primary);
border-radius: 1.25rem;
box-shadow: .35rem .35rem var(--color-shadow);
margin: 2rem 0;
text-decoration: none;
/* Click animation handling */
position: relative;
top: 0;
left: 0;
transition: top .05s ease-in, left .05s ease-in;
}
.postlink:focus-visible,
.taglink:focus-visible {
background-color: var(--color-primary);
outline: none;
}
@media (any-hover: hover) {
.postlink:hover,
.taglink:hover {
background-color: var(--color-primary);
}
}
/* Forced colors */
@media (forced-colors: active) {
.postlink:focus-visible,
.taglink:focus-visible {
outline-offset: .25rem;
outline: .25rem solid;
}
@media (any-hover: hover) {
.postlink:hover,
.taglink:hover {
outline-offset: .25rem;
outline: .25rem solid;
}
}
}
/* Click animation */
.postlink:active,
.taglink:active {
box-shadow: none;
top: .2rem;
left: .2rem;
box-shadow: .15rem .15rem var(--color-shadow);
}
/* Post & tag elements */
.post h2, .post img,
.post ul, .post li,
.tag h2, .tag p,
.tag img {
margin: 0;
}
.post h2,
.tag h2 {
grid-area: h2;
padding: .25rem .5rem;
text-transform: uppercase;
font-size: 1.5rem;
color: var(--color-primary);
border-radius: 1rem 1rem 0 0;
border-bottom: .25rem solid var(--color-accent);
}
.post:nth-child(even) h2,
.tag:nth-child(even) h2 {
text-align: right;
}
.postlink:focus-visible h2,
.taglink:focus-visible h2 {
color: var(--color-bg);
border-color: var(--color-bg);
}
@media (any-hover: hover) {
.postlink:hover h2,
.taglink:hover h2 {
color: var(--color-bg);
border-color: var(--color-bg);
}
}
/* Images */
.post img,
.tag-imgs {
grid-area: img;
}
.blur {
filter: blur(.75rem);
clip-path: inset(0 round 1rem);
}
.tag-imgs {
display: grid;
grid-template-columns: repeat(2, 1fr);
gap: .15rem;
}
.tag-imgs img {
aspect-ratio: 3 / 2;
object-fit: cover;
}
.missing-image {
width: 100%;
aspect-ratio: 3 / 2;
background-color: var(--color-bg-alt);
border-radius: 1rem;
}
.taglink:focus-visible .missing-image {
opacity: .7;
}
@media (any-hover: hover) {
.taglink:hover .missing-image {
opacity: .7;
}
}
/* Post tags */
.postlist-tags {
grid-area: info;
list-style: none;
display: flex;
flex-flow: row wrap;
gap: .5rem;
padding: .5rem;
}
.post:nth-child(odd) .postlist-tags {
justify-content: flex-end;
}
.postlist-tags li,
.tagcount {
background-color: var(--color-primary);
color: var(--color-bg);
padding: 0 .5rem;
border-radius: 1rem;
}
.postlink:focus-visible .postlist-tags li,
.taglink:focus-visible .tagcount {
background-color: var(--color-bg);
color: var(--color-primary);
}
@media (any-hover: hover) {
.postlink:hover .postlist-tags li,
.taglink:hover .tagcount {
background-color: var(--color-bg);
color: var(--color-primary);
}
}
/* Tag count */
.tag p {
grid-area: info;
padding: .5rem;
}
.tag:nth-child(odd) p {
text-align: right;
}
img[tabindex="0"] {
cursor: pointer;
}
img[tabindex="0"]:focus-visible {
outline: .15rem solid var(--color-teal);
}
dialog {
margin: auto;
flex-flow: column;
background: transparent;
border: none;
position: absolute;
}
dialog[open] {
display: flex;
}
dialog::backdrop {
background-color: rgba(from var(--color-bg) r g b / .8);
backdrop-filter: blur(4px);
}
body:has(dialog[open]) {
overflow: hidden;
}
.close-dialog {
background-color: rgba(from var(--color-teal) r g b / .35);
font-size: 1.5rem;
padding: 0 .5rem .15rem;
border-radius: 1rem;
color: var(--color-teal);
box-shadow: .15rem .15rem var(--color-shadow);
border: .08rem solid var(--color-teal);
align-self: flex-end;
justify-self: flex-start;
margin: 0 .1rem;
/* Click animation handling */
position: relative;
top: 1rem;
left: -.15rem;
transition: top .1s ease-in, left .1s ease-in;
}
.close-dialog:focus-visible {
outline: none;
background-color: var(--color-teal);
color: var(--color-bg);
}
@media (any-hover: hover) {
.close-dialog:hover {
outline: none;
background-color: var(--color-teal);
color: var(--color-bg);
}
}
@media (forced-colors: active) {
.close-dialog:focus-visible {
outline-offset: .08rem;
outline: .08rem solid;
}
@media (any-hover: hover) {
.close-dialog:hover {
outline-offset: .08rem;
outline: .08rem solid;
}
}
}
/* Click animation */
.close-dialog:active {
top: 1.1rem;
left: -.05rem;
box-shadow: .05rem .05rem var(--color-shadow);
}
.modal-img {
max-height: calc(90vh - 2rem);
object-fit: contain;
width: auto;
max-width: 90%;
margin: 0 auto;
}
:root {
color-scheme: light dark;
--font-family: 'Atkinson Hyperlegible Next', sans-serif;
--font-family-code: 'Atkinson Hyperlegible Mono', monospace;
--color-dark: #2e303e;
--color-dark-alt: #3c3f52;
--color-light: #ebeeef;
--color-light-alt: #dbe1e3;
--color-teal-dark: #18737b;
--color-teal-light: #25b0bc;
--color-pink-dark: #94195d;
--color-pink-light: #ee9fcb;
--color-shadow: rgba(2, 10, 40, .25);
/* Used for syntax highlighting */
--color-red-light: #f195aa;
--color-orange-light: #fab795;
--color-yellow-light: #fbe6bc;
--color-green-light: #29d398;
--color-blue-light: #26bbd9;
--color-purple-light: #ddaeea;
--color-grey-light: #b9c3c6;
--color-red-dark: #991433;
--color-orange-dark: #883206;
--color-yellow-dark: #6a4906;
--color-green-dark: #125940;
--color-blue-dark: #125663;
--color-purple-dark: #722999;
--color-grey-dark: #4a4b64;
--color-text: light-dark(var(--color-dark), var(--color-light));
--color-bg: light-dark(var(--color-light), var(--color-dark));
--color-text-alt: light-dark(var(--color-dark-alt), var(--color-light-alt));
--color-bg-alt: light-dark(var(--color-light-alt), var(--color-dark-alt));
--color-teal: light-dark(var(--color-teal-dark), var(--color-teal-light));
--color-pink: light-dark(var(--color-pink-dark), var(--color-pink-light));
--color-red: light-dark(var(--color-red-dark), var(--color-red-light));
--color-orange: light-dark(var(--color-orange-dark), var(--color-orange-light));
--color-yellow: light-dark(var(--color-yellow-dark), var(--color-yellow-light));
--color-green: light-dark(var(--color-green-dark), var(--color-green-light));
--color-blue: light-dark(var(--color-blue-dark), var(--color-blue-light));
--color-purple: light-dark(var(--color-purple-dark), var(--color-purple-light));
--color-grey: light-dark(var(--color-grey-dark), var(--color-grey-light));
}
/* Base */
* {
box-sizing: border-box;
margin: 0;
padding: 0;
}
body {
font-family: var(--font-family);
color: var(--color-text);
background-color: var(--color-bg);
}
main {
width: 60vw;
max-width: 1000px;
margin: 0 auto;
scroll-margin-top: 7rem;
}
@media (max-width: 1050px) {
main {
width: 75vw;
}
}
@media (max-width: 650px) {
main {
width: 92vw;
}
}
/* Headers */
h1, h2, h3, h4, h5, h6 {
line-height: 1.25;
color: var(--color-teal);
}
h1 {
margin-top: 3rem;
font-size: 3.5rem;
text-align: center;
}
h2, h3, h4, h5, h6 {
scroll-margin-top: 5rem;
}
h2 {
margin-top: 2rem;
font-size: 2.2rem;
}
h3 {
margin-top: 1.5rem;
font-size: 1.6rem;
}
@media (max-width: 650px) {
h1 { font-size: 2.8rem; }
h2 { font-size: 1.8rem; }
h3 { font-size: 1.35rem; }
}
h4, h5, h6 {
margin-top: 1rem;
font-size: 1.2rem;
}
/* Images */
img {
display: block;
max-width: 100%;
height: auto;
border-radius: 1rem;
margin: 0 auto;
}
/* Paragraphs */
p {
margin: 1.25rem 0;
line-height: 1.4;
}
strong,
b {
font-weight: 900;
}
/* Links */
a {
color: var(--color-text);
border-radius: .25rem;
text-decoration: underline;
text-decoration-style: solid;
text-decoration-thickness: .2em;
text-decoration-color: var(--color-teal);
transition: text-decoration-thickness .5s;
}
a:focus-visible {
text-decoration: none;
outline: .15rem solid var(--color-teal);
}
@media (any-hover: hover) {
a:hover {
text-decoration-thickness: .4em;
}
}
a:active {
text-decoration-thickness: .4em;
}
/* Heading anchors */
a.ha,
span.ha-placeholder {
color: var(--color-pink);
font-size: .8em;
vertical-align: .1em;
}
span.ha-placeholder {
opacity: .55;
}
/* Lists */
::marker {
color: var(--color-pink);
}
ul, ol, dl, li {
margin-left: 1rem;
}
@media (max-width: 650px) {
ul, ol, dl {
margin-left: 0;
}
}
li {
line-height: 1.2 5;
margin-top: .65rem;
margin-bottom: .65rem;
}
li ul, li ol {
margin: .5rem 0;
}
dt {
font-weight: 900;
margin-top: .5rem;
}
dd {
margin-left: 2rem;
margin-bottom: .75rem;
}
/* Blockquotes */
blockquote {
margin: .5rem 0;
padding: 0 1rem;
border-radius: .25rem 1rem 1rem .25rem;
line-height: 1.25;
border-left: .5rem solid var(--color-pink);
}
blockquote,
blockquote p,
blockquote ol,
blockquote ul {
background-color: var(--color-bg-alt);
padding: .5rem;
}
blockquote p {
margin: 0;
}
/* Tables */
table {
width: 100%;
border-spacing: 0; /* border collapse doesn't play nice with radii */
border-radius: .3rem;
border: thin solid var(--color-pink);
}
th {
color: var(--color-bg);
background-color: var(--color-pink);
}
th code {
color: var(--color-text); /* Yes, I actually do this somewhere */
}
th, td {
padding: .5rem;
text-align: left;
}
tr:nth-child(even) { background-color: var(--color-bg-alt); }
th:not(:first-child) { border-left: thin solid var(--color-bg); }
th:first-child { border-top-left-radius: .25rem; }
th:last-child { border-top-right-radius: .25rem; }
td:not(:first-child) { border-left: thin solid var(--color-pink); }
/* Times */
time {
color: var(--color-grey);
}
/* Horizontal rules */
hr {
border: .25rem solid var(--color-pink);
margin: 2rem 0;
}
/* Used on home, reference, gallery pages */
.centered {
text-align: center;
}
/* Currently only used for resume, but it's generalizable */
.upper {
text-transform: uppercase;
}
/* Header */
header {
position: sticky;
top: 0;
background-color: var(--color-bg);
padding: .75rem 0;
z-index: 10;
border-bottom: thick solid var(--color-teal);
box-shadow: 0 .25rem .15rem var(--color-shadow);
}
/* Header links, pagination links */
header a,
.pagination a,
.webring ul a {
border-radius: 1rem;
border: .125rem solid var(--color-pink);
color: var(--color-pink);
text-decoration: none;
padding: 0 .25rem;
box-shadow: .15rem .15rem var(--color-shadow);
font-size: 1.2rem;
/* Click animation handling */
position: relative;
top: 0;
left: 0;
transition: top .05s ease-in, left .05s ease-in;
}
header a,
.pagination .older a,
.webring .prev a,
.webring .rand a {
padding-right: .35rem;
}
.pagination .newer a,
.webring .next a,
.webring .rand a {
padding-left: .35rem;
}
header a:focus-visible,
.pagination a:focus-visible,
.webring ul a:focus-visible {
color: var(--color-bg);
border-color: var(--color-pink);
background-color: var(--color-pink);
outline: none;
}
@media (any-hover: hover) {
header a:hover,
.pagination a:hover,
.webring ul a:hover {
color: var(--color-bg);
border-color: var(--color-pink);
background-color: var(--color-pink);
}
}
@media (forced-colors: active) {
header a:focus-visible,
.pagination a:focus-visible,
.webring ul a:focus-visible {
outline-offset: .125rem;
outline: .125rem solid;
}
@media (any-hover: hover) {
header a:hover,
.pagination a:hover,
.webring ul a:hover {
outline-offset: .125rem;
outline: .125rem solid;
}
}
}
/* Click animation */
header a:active,
.pagination a:active,
.webring ul a:active {
top: .1rem;
left: .1rem;
box-shadow: .05rem .05rem var(--color-shadow);
}
/* Current page */
header a[aria-current="page"] {
border-color: var(--color-teal);
color: var(--color-teal);
}
header a[aria-current="page"]:focus-visible {
color: var(--color-bg);
border-color: var(--color-teal);
background-color: var(--color-teal);
}
@media (any-hover: hover) {
header a[aria-current="page"]:hover {
color: var(--color-bg);
background-color: var(--color-teal);
border-color: var(--color-teal);
}
}
/* Header link icons, pagination icons */
header i,
.pagination i,
.webring ul i {
color: var(--color-teal);
}
header i,
.pagination .older i,
.webring .prev i,
.webring .rand i:nth-child(1) {
padding-left: .25rem;
}
.pagination .newer i,
.webring .next i,
.webring .rand i:nth-child(2) {
padding-right: .25rem;
}
header a[aria-current="page"] i {
color: var(--color-pink);
}
header a:focus-visible i,
a[aria-current="page"] a:focus-visible i,
.pagination a:focus-visible i,
.webring ul a:focus-visible i {
color: var(--color-bg);
}
@media (any-hover: hover) {
header a:hover i,
header a[aria-current="page"]:hover i,
.pagination a:hover i,
.webring ul a:hover i {
color: var(--color-bg);
}
}
/* Skip link */
#skip {
left: -999px;
position: absolute;
top: auto;
width: 1px;
height: 1px;
overflow: hidden;
z-index: -99;
}
#skip:focus-visible {
display: inline-block;
left: auto;
top: auto;
width: auto;
height: auto;
overflow: auto;
margin: 0 10%;
z-index: 999;
}
/* Nav */
header ul {
display: flex;
list-style: none;
gap: 1rem;
justify-content: center;
}
header ul,
header li {
margin: 0;
}
@media (max-width: 650px) {
.menu-text {
display: none; /* Icons only on small screens */
}
header a {
padding: .15rem .5rem;
}
header i {
padding: 0;
}
}
/* Footer */
footer {
padding: 1rem 0;
font-size: .9rem;
border-top: thick solid var(--color-pink);
margin-top: 2rem;
}
footer ul {
display: flex;
list-style: none;
gap: .5rem;
justify-content: center;
margin: 0;
}
footer li {
margin: 0;
}
footer li:nth-child(2)::before,
footer li:nth-child(2)::after {
content: " ● " / "";
color: var(--color-teal);
}
@media (max-width: 650px) {
footer ul {
flex-flow: column;
text-align: center;
}
footer li:nth-child(2)::before,
footer li:nth-child(2)::after {
content: none;
}
}
footer a {
text-decoration-color: var(--color-pink);
}
footer a:focus-visible {
outline-color: var(--color-pink);
}
/* Pagination */
.pagination,
.pagination li {
margin: 0;
}
.pagination {
display: grid;
grid-template-columns: repeat(2, 1fr);
grid-template-areas: "older newer";
list-style: none;
margin-top: 3rem;
}
@media (max-width: 650px) {
.post-pagination {
grid-template-columns: 1fr;
grid-template-areas:
"older"
"newer";
gap: .75rem;
}
}
.pagination .older {
grid-area: older;
}
.pagination .newer {
grid-area: newer;
text-align: right;
}
/* webring navigation */
.webring {
margin-bottom: 3rem;
}
.webring ul {
display: flex;
flex-flow: row wrap;
list-style: none;
justify-content: space-around;
gap: .35rem;
}
.webring ul,
.webring li {
margin-left: 0;
}
@media print {
/* Nav elements */
header,
footer,
nav {
display: none !important;
}
/* Base */
body {
background-color: #fff;
color: #000;
}
main {
width: 95vw;
}
h1,h2,h3,h4,h5,h6 {
color: #000;
}
/* Links */
/* Hover is not really necessary, but it's annoying when testing otherwise */
a,
a:hover {
text-decoration-style: dotted;
text-decoration-thickness: .1rem;
text-decoration-color: #000;
}
a::after{
content: " (" attr(href) ")";
}
/* Code */
code,
pre,
code[class*=language-],
pre[class*=language-] {
text-shadow: none;
background-color: var(--color-light);
color: #000 !important;
}
.token.namespace {
opacity: 1;
}
.token.block-comment,
.token.cdata,
.token.comment,
.token.doctype,
.token.prolog,
.token.punctuation,
.token.attr-name,
.token.deleted,
.token.namespace,
.token.tag,
.token.boolean,
.token.function,
.token.number,
.token.class-name,
.token.constant,
.token.property,
.token.symbol,
.token.attr-value,
.token.char,
.token.regex,
.token.string,
.token.variable,
.token.inserted,
.token.entity,
.token.operator,
.token.url,
.token.function-name,
.token.atrule,
.token.builtin,
.token.important,
.token.keyword,
.token.selector {
color: #000;
}
}</style>
<script type="module">// Thank you to https://github.com/daviddarnes/heading-anchors
// Thank you to https://amberwilson.co.uk/blog/are-your-anchor-links-accessible/
let globalInstanceIndex = 0;
class HeadingAnchors extends HTMLElement {
static register(tagName = "heading-anchors", registry = window.customElements) {
if(registry && !registry.get(tagName)) {
registry.define(tagName, this);
}
}
static attributes = {
exclude: "data-ha-exclude",
prefix: "prefix",
content: "content",
}
static classes = {
anchor: "ha",
placeholder: "ha-placeholder",
srOnly: "ha-visualhide",
}
static defaultSelector = "h2,h3,h4,h5,h6";
static css = `
.${HeadingAnchors.classes.srOnly} {
clip: rect(0 0 0 0);
height: 1px;
overflow: hidden;
position: absolute;
width: 1px;
}
.${HeadingAnchors.classes.anchor} {
position: absolute;
left: var(--ha_offsetx);
top: var(--ha_offsety);
text-decoration: none;
opacity: 0;
}
.${HeadingAnchors.classes.placeholder} {
opacity: .3;
}
.${HeadingAnchors.classes.anchor}:is(:focus-within, :hover) {
opacity: 1;
}
.${HeadingAnchors.classes.anchor},
.${HeadingAnchors.classes.placeholder} {
display: inline-block;
padding: 0 .25em;
/* Disable selection of visually hidden label */
-webkit-user-select: none;
user-select: none;
}
@supports (anchor-name: none) {
.${HeadingAnchors.classes.anchor} {
position: absolute;
left: anchor(left);
top: anchor(top);
}
}`;
get supports() {
return "replaceSync" in CSSStyleSheet.prototype;
}
get supportsAnchorPosition() {
return CSS.supports("anchor-name: none");
}
constructor() {
super();
if(!this.supports) {
return;
}
let sheet = new CSSStyleSheet();
sheet.replaceSync(HeadingAnchors.css);
document.adoptedStyleSheets = [...document.adoptedStyleSheets, sheet];
this.headingStyles = {};
this.instanceIndex = globalInstanceIndex++;
}
connectedCallback() {
if (!this.supports) {
return;
}
this.headings.forEach((heading, index) => {
if(!heading.hasAttribute(HeadingAnchors.attributes.exclude)) {
let anchor = this.getAnchorElement(heading);
let placeholder = this.getPlaceholderElement();
// Prefers anchor position approach for better accessibility
// https://amberwilson.co.uk/blog/are-your-anchor-links-accessible/
if(this.supportsAnchorPosition) {
let anchorName = `--ha_${this.instanceIndex}_${index}`;
placeholder.style.setProperty("anchor-name", anchorName);
anchor.style.positionAnchor = anchorName;
}
heading.appendChild(placeholder);
heading.after(anchor);
}
});
}
// Polyfill-only
positionAnchorFromPlaceholder(placeholder) {
if(!placeholder) {
return;
}
let heading = placeholder.closest("h1,h2,h3,h4,h5,h6");
if(!heading.nextElementSibling) {
return;
}
// TODO next element could be more defensive
this.positionAnchor(heading.nextElementSibling);
}
// Polyfill-only
positionAnchor(anchor) {
if(!anchor || !anchor.previousElementSibling) {
return;
}
// TODO previous element could be more defensive
let heading = anchor.previousElementSibling;
this.setFontProp(heading, anchor);
if(this.supportsAnchorPosition) {
// quit early
return;
}
let placeholder = heading.querySelector(`.${HeadingAnchors.classes.placeholder}`);
if(placeholder) {
anchor.style.setProperty("--ha_offsetx", `${placeholder.offsetLeft}px`);
anchor.style.setProperty("--ha_offsety", `${placeholder.offsetTop}px`);
}
}
setFontProp(heading, anchor) {
let placeholder = heading.querySelector(`.${HeadingAnchors.classes.placeholder}`);
if(placeholder) {
let style = getComputedStyle(placeholder);
let props = ["font-weight", "font-size", "line-height", "font-family"];
let [weight, size, lh, family] = props.map(name => style.getPropertyValue(name));
anchor.style.setProperty("font", `${weight} ${size}/${lh} ${family}`);
let vars = style.getPropertyValue("font-variation-settings");
if(vars) {
anchor.style.setProperty("font-variation-settings", vars);
}
}
}
/* no longer used, using aria-labelledby instead - see getAnchorElement
getAccessibleTextPrefix() {
// Useful for i18n
return this.getAttribute(HeadingAnchors.attributes.prefix) || "Jump to section titled";
}
*/
getContent() {
if(this.hasAttribute(HeadingAnchors.attributes.content)) {
return this.getAttribute(HeadingAnchors.attributes.content);
}
return "#";
}
// Placeholder nests inside of heading
getPlaceholderElement() {
let ph = document.createElement("span");
ph.setAttribute("aria-hidden", true);
ph.classList.add(HeadingAnchors.classes.placeholder);
let content = this.getContent();
if(content) {
ph.innerHTML = content; // CHANGED HERE
}
ph.addEventListener("mouseover", (e) => {
let placeholder = e.target.closest(`.${HeadingAnchors.classes.placeholder}`);
if(placeholder) {
this.positionAnchorFromPlaceholder(placeholder);
}
});
return ph;
}
getAnchorElement(heading) {
let anchor = document.createElement("a");
anchor.href = `#${heading.id}`;
anchor.classList.add(HeadingAnchors.classes.anchor);
let content = this.getContent();
anchor.innerHTML = `<span aria-labelledby=${heading.id}>${content}</span>`; // CHANGED HERE
anchor.addEventListener("focus", e => {
let anchor = e.target.closest(`.${HeadingAnchors.classes.anchor}`);
if(anchor) {
this.positionAnchor(anchor);
}
});
anchor.addEventListener("mouseover", (e) => {
// when CSS anchor positioning is supported, this is only used to set the font
let anchor = e.target.closest(`.${HeadingAnchors.classes.anchor}`);
this.positionAnchor(anchor);
});
return anchor;
}
get headings() {
return this.querySelectorAll(this.selector.split(",").map(entry => `${entry.trim()}[id]`));
}
get selector() {
return this.getAttribute("selector") || HeadingAnchors.defaultSelector;
}
}
HeadingAnchors.register();
export { HeadingAnchors }
/* don't even bother on mobile */
if (window.innerWidth > 650) {
const dialog = document.querySelector("dialog");
const closeButton = document.querySelector(".close-dialog");
const hero = document.querySelector(".hero");
hero.tabIndex = 0;
hero.addEventListener("click", (e) => dialog.showModal());
hero.addEventListener("keydown", (e) => {
if (e.key === "Enter" || e.key === " ") {
e.preventDefault();
dialog.showModal();
}
});
closeButton.addEventListener("click", (e) => dialog.close());
closeButton.addEventListener("keydown", (e) => {
if (e.key === "Enter" || e.key === " ") {
e.preventDefault();
dialog.close();
}
});
}</script>
</head>
<body>
<header>
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<heading-anchors content="<i class='fa-solid fa-anchor'></i>">
<article>
<h1 id="accessible-image-modals">accessible image modals</h1>
<div class="post-metadata">
<p>
posted on
<time datetime="2026-03-22">March 22, 2026</time>
by Lee Cattarin
</p>
<ul class="post-tags">
<li>
<a href="/tags/software/">software</a>
</li>
</ul>
</div>
<dialog closedby="any" aria-label="image modal" tabindex="-1">
<button class="close-dialog" autofocus="" aria-label="close the image modal">&times;</button>
<img class="modal-img" src="/img/snacking-seagull.jpg" alt="Image unrelated to post. A seagull floating in the water with a starfish hanging out of eir mouth." loading="lazy" decoding="async" width="1000" height="666">
</dialog>
<img class="hero" src="/img/snacking-seagull.jpg" alt="Image unrelated to post. A seagull floating in the water with a starfish hanging out of eir mouth." loading="lazy" decoding="async" width="1000" height="666">
<p>Recently I've been working on a single-page digital rendition of a zine complete with many hand-drawn images. The author wanted to be able to bring images up to a full-screen view, to either zoom in or to put the whole enlarged image on one screen with no scrolling. It was a real struggle to find resources on how to do this in an accessible manner, so I'm writing up what I did.</p>
<blockquote>
<p>Fair warning: This solution is likely imperfect.</p>
</blockquote>
<h2 id="the-dialog-element">the <code>dialog</code> element</h2>
<p>do you know how many tutorials want you to roll your own modals? It's a not-insignificant amount. W3Schools, top of the search results in many cases, recommends it in two places - <a href="https://www.w3schools.com/howto/howto_css_modal_images.asp" target="_blank" rel="external">image modals</a> and <a href="https://www.w3schools.com/css/css3_images_modal.asp" target="_blank" rel="external">responsive image modals</a>. Several search results for &quot;image modal&quot; pop up div solutions - <a href="https://stackoverflow.com/questions/75598914/how-to-display-an-image-clicking-on-it-using-modal-window-on-html-css-and-js" target="_blank" rel="external">div modal 1</a>, <a href="https://dev.to/salehmubashar/create-an-image-modal-with-javascript-2lf3" target="_blank" rel="external">div modal 2</a>, <a href="https://www.youtube.com/watch?v=Y9TNHynFjaQ" target="_blank" rel="external">div modal 3</a>.</p>
<p>If you don't know of the existence of <code>&lt;dialog&gt;</code>, a search for image modals will not get you there quickly.</p>
<p>If you search for <em>accessible</em> image modals, you'll still hear about <code>&lt;div&gt;</code>s. Hell, <a href="https://www.w3.org/WAI/ARIA/apg/patterns/dialog-modal/examples/dialog/" target="_blank" rel="external">W3C's ARIA Authoring Practices Guide uses a <code>&lt;div&gt;</code></a>. You kinda have to go digging to read about the <a href="https://www.scottohara.me/blog/2023/01/26/use-the-dialog-element.html" target="_blank" rel="external">dialog element from Scott O'Hara</a> or find <a href="https://accessibleweb.dev/modals" target="_blank" rel="external">AccessibleWeb.dev's piece on modals</a>. Or you can go <a href="https://adrianroselli.com/2025/06/where-to-put-focus-when-opening-a-modal-dialog.html" target="_blank" rel="external">straight for Adrian Roselli</a> and find examples that use the native <code>&lt;dialog&gt;</code> element. Thanks Adrian!</p>
<p>Did I roll my own modal at first? Regretfully, yes. I'd used the <code>&lt;dialog&gt;</code> element before... several years ago... in a project I don't have access to anymore... Needless to say, I had forgotten about its existence.</p>
<p>Anyway, I got there. Eventually. So let's talk about modals and <code>&lt;dialog&gt;</code>.</p>
<h3 id="what-does-dialog-give-us">what does <code>&lt;dialog&gt;</code> give us?</h3>
<p>so, what do we get from the <code>&lt;dialog&gt;</code> element that we don't get from a <code>&lt;div&gt;</code> modal?</p>
<ol>
<li>a semantically meaningful element</li>
<li>a backdrop that fills the screen behind the modal, styleable with <code>::backdrop</code></li>
<li>automatic use of the <code>Esc</code> key to close the modal</li>
<li>automatic focus trapping that prevents any tabbing within the page behind the modal (users can tab off the page into the browser buttons)</li>
<li>the JS functions <code>.showModal()</code> and <code>.close()</code></li>
<li>if <code>closedby</code> is set to <code>any</code>, clicking outside the modal (anywhere on the backdrop) will also close the modal</li>
<li>automatic return of focus to the element that triggered the modal</li>
<li>the <code>autofocus</code> attribute for in-modal elements to set which element should receive focus on opening the modal</li>
<li>the <code>open</code> attribute which is set on the <code>&lt;dialog&gt;</code> when open and removed when closed (when you use the functions mentioned previously)</li>
</ol>
<p>and more. This is just the pieces in use for me. There's also things like <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/dialog#additional_notes" target="_blank" rel="external">setting forms so that submission closes the dialog</a> (point 1 in that list).</p>
<h3 id="what-doesnt-it-give-us">what doesn't it give us?</h3>
<ol>
<li>a close button - gotta roll your own and attach the requisite <code>.close()</code> call (or rely on users hitting escape or clicking the backdrop)</li>
<li>prevention of scroll on the rest of the page</li>
</ol>
<h3 id="a-bug">a bug</h3>
<p>MDN warns:</p>
<blockquote>
<p>Do not add the <code>tabindex</code> property to the <code>&lt;dialog&gt;</code> element as it is not interactive and does not receive focus.</p>
</blockquote>
<p>— <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/dialog#additional_notes" target="_blank" rel="external"><code>&lt;dialog&gt;</code>: additional notes</a> (point 3 in that list).</p>
<p>despite this, I found that in Firefox (but not Edge), the <em><code>&lt;dialog&gt;</code> itself was focusable</em>. I have no idea why, but I tested this on a totally unstyled and unmodified page and still found it to be true. As a focusable element, it made no sense. It had no interactivity and could not be activated.</p>
<p>I'm still torn: do I add <code>tabindex=&quot;-1&quot;</code>? MDN specifically says not to, but I'm pretty sure they're warning against making it <em>focusable</em>. Why warn against making it nonfocusable when <em>it's not supposed to be focusable in the first place</em>, after all?</p>
<p>At current, I'm ambivalent, but I've added <code>tabindex=&quot;-1&quot;</code> to handle Firefox's poor behavior. Making the dialog focusable is unhelpful and confusing.</p>
<h2 id="in-addition-to-the-dialog">in addition to the <code>&lt;dialog&gt;</code></h2>
<p>here's what else I wrote...</p>
<h3 id="html">html</h3>
<p>besides the <code>&lt;dialog&gt;</code>, I gave my <code>&lt;img&gt;</code> elements <code>tabindex=&quot;0&quot;</code> to make them focusable.</p>
<h3 id="js">js</h3>
<p>in <code>modal.js</code>, I created an <code>openDialog()</code> function that takes in the clicked image. It:</p>
<ul>
<li>creates a new <code>&lt;img&gt;</code> element and copies over the <code>src</code> and <code>alt</code> attributes - importantly, it doesn't copy the full <code>&lt;img&gt;</code> because we <em>don't</em> want to copy that <code>tabindex</code> attribute</li>
<li>replaces the current <code>&lt;img&gt;</code> in the modal with our new copy with <code>replaceChild()</code> (or if there's no current one, it just appends)</li>
<li>calls <code>dialog.showModal()</code></li>
</ul>
<p>I gave my close button two event listeners, one that listens for click events and one that listens for a keydown of the space or enter keys. In the case of the keydown, it calls <code>event.preventDefault()</code> to stop the space key from scrolling the underlying page.</p>
<p>I also looped through all images and attached my <code>openDialog()</code> function to any image with a <code>tabindex</code> attribute (I had some images that weren't intended to be fullscreened, so they lacked <code>tabindex</code>). Again, I gave them listeners on both click and keydown.</p>
<h3 id="css">css</h3>
<p>here's the most relevant parts of the CSS:</p>
<ul>
<li><code>dialog::backdrop</code> was given a <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Colors/Using_relative_colors" target="_blank" rel="external">relatively calculated</a> color - <code>rgba(from var(--color-bg) r g b / .8)</code> - as well as a blur</li>
<li><code>body:has(dialog[open])</code> has <code>overflow: hidden</code> set</li>
<li><code>dialog img</code> uses a <code>max-height</code> as well as <code>object-fit: contain</code></li>
</ul>
<h2 id="errors-questions">errors? questions?</h2>
<p>reach out!</p>
</article>
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drone build Sun Jul 26 14:52:19 PDT 2026
2026-07-26 21:52:19 +00:00
<a class="postlink" href="/core-css/">
<h2 data-ha-exclude="" id="core-css">core CSS </h2>
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<ul class="postlist-tags">
<li>software</li>
</ul>
drone build Sun Jul 26 14:52:19 PDT 2026
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<img src="/img/core-css.png" alt="A website mockup in dark mode with light pink accents. Everything is filler text such as the title &#39;This is my cool website&#39;, headers reading things like &#39;This is an h1&#39;, nav items &#39;Nav item 1&#39;, etc. There is a paragraph block - the opening of the Bee Movie - and part of an image visible - a screencap of the music video for Never Gonna Give You Up by Rick Astley." loading="lazy" decoding="async" width="1000" height="447">
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drone build Sun Jul 26 14:52:19 PDT 2026
2026-07-26 21:52:19 +00:00
<a class="postlink" href="/moving-images/">
<h2 data-ha-exclude="" id="moving-images">moving images </h2>
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drone build Sun Jul 26 14:52:19 PDT 2026
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<img src="/img/cormorant.jpg" alt="Image unrelated to post. A cormorant, a type of black waterfowl, poses with wings spread on a buoy in Puget Sound. Off to the left, another bird floats." loading="lazy" decoding="async" width="1000" height="666">
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drone build Sun Jul 26 14:52:19 PDT 2026
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<h2 data-ha-exclude="" id="redirections">redirections </h2>
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drone build Sun Jul 26 14:52:19 PDT 2026
2026-07-26 21:52:19 +00:00
<img src="/img/angle-brackets-uwu.jpg" alt="Ascii art of an emoticon with pinched eyes and a small mouth made with two angle brackets." loading="lazy" decoding="async" width="1000" height="316">
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