djpogo/css-theming-rethought.html

## css-theming-rethought.html
<!DOCTYPE html>
<html lang="de">
<head>
    <title>I'm in the mode</title>
    <meta charset="utf-8">

    <meta name="description" content="Sometimes I ran…">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link href="https://fonts.googleapis.com/css?family=Big+Shoulders+Text&display=swap" rel="stylesheet">
    <script>
        (function () {
            var theme = window.localStorage.getItem("theme");
            if (theme) {
                document.documentElement.dataset.theme = theme;
            }
        }());
    </script>

    <script>
        (function() {
            var mqDark = window.matchMedia('(prefers-color-scheme: dark)');
            var mqLight = window.matchMedia('(prefers-color-scheme: light)');
            var theme = window.localStorage.getItem('theme');

            function checkTheme(event) {
                if (event.matches) {
                    if (event.media.includes('dark')) {
                        document.documentElement.dataset.theme = 'dark';
                    }
                    if (event.media.includes('light')) {
                        document.documentElement.dataset.theme = 'light';
                    }
                }
            }

            if (mqDark.matches && !theme) {
                // don't store in localStorage because it is not a user setting
                document.documentElement.dataset.theme = 'dark';
            }

            if (mqLight.matches && !theme) {
                // don't store in localStorage because it is not a user setting
                document.documentElement.dataset.theme = 'light';
            }

            if (!theme) {
                try {
                    mqDark.addEventListener('change', checkTheme);
                    mqLight.addEventListener('change', checkTheme);
                } catch (maybeSafari) {
                    try {
                        mqDark.addListener(checkTheme);
                        mqLight.addListener(checkTheme);
                    } catch (dontknow) {
                        // not supported…
                    }
                }
            }
        }());
    </script>
    <script>
        (function() {
            var theme = window.localStorage.getItem('theme');

            function revokeTheme() {
                if (!window.confirm('Do you want to stay with that theme?')) {
                    window.localStorage.removeItem('theme');
                    document.documentElement.dataset.theme = null;
                }
            }

            if (!theme) {
                if (window.confirm('This page offers a "dark" theme, you want to try it?')) {
                    window.localStorage.setItem('theme', 'dark');
                    document.documentElement.dataset.theme = 'dark';
                    window.setTimeout(revokeTheme, 3000);
                } else {
                    window.localStorage.setItem('theme', 'light');
                    document.documentElement.dataset.theme = 'light';
                }
            }
        }())
    </script>
    <style>
        :root {
            --bg-color: hsla(0, 0%, 90%, 1);
            --text-color: hsla(0, 0%, 20%, 1);
        }
        *,
        *::before,
        *::after {
            box-sizing: border-box;
        }
        html {
            width: 100vw;
            height: 100vh;
            max-width: 100%;
            min-height: 100%;
            display: flex;
            overflow-x: hidden;
            margin: 0;
            align-items: center;
            justify-content: center;
        }

        body {
            background-color: var(--bg-color);
            color: var(--text-color);
            font-family: 'Big Shoulders Text', cursive;
            transition: color .2s ease-in, background-color .2s ease-out;
        }
        .mode::after {
            content: "light";
        }

        html[data-theme="dark"] {
            --bg-color: hsla(0, 0%, 20%, 1);
            --text-color: hsla(0,0%, 80%, 1);
        }
        html[data-theme="dark"] .mode::after {
            content: "dark";
        }
    </style>
</head>
<body>
    <section class="hero">
        <h1>Welcome to the <span class="mode"></span> mode</h1>
    </section>
</body>
</html>
	<!DOCTYPE html>
	<html lang="de">
	<head>
	<title>I'm in the mode</title>
	<meta charset="utf-8">

	<meta name="description" content="Sometimes I ran…">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<link href="https://fonts.googleapis.com/css?family=Big+Shoulders+Text&display=swap" rel="stylesheet">
	<script>
	(function () {
	var theme = window.localStorage.getItem("theme");
	if (theme) {
	document.documentElement.dataset.theme = theme;
	}
	}());
	</script>

	<script>
	(function() {
	var mqDark = window.matchMedia('(prefers-color-scheme: dark)');
	var mqLight = window.matchMedia('(prefers-color-scheme: light)');
	var theme = window.localStorage.getItem('theme');

	function checkTheme(event) {
	if (event.matches) {
	if (event.media.includes('dark')) {
	document.documentElement.dataset.theme = 'dark';
	}
	if (event.media.includes('light')) {
	document.documentElement.dataset.theme = 'light';
	}
	}
	}

	if (mqDark.matches && !theme) {
	// don't store in localStorage because it is not a user setting
	document.documentElement.dataset.theme = 'dark';
	}

	if (mqLight.matches && !theme) {
	// don't store in localStorage because it is not a user setting
	document.documentElement.dataset.theme = 'light';
	}

	if (!theme) {
	try {
	mqDark.addEventListener('change', checkTheme);
	mqLight.addEventListener('change', checkTheme);
	} catch (maybeSafari) {
	try {
	mqDark.addListener(checkTheme);
	mqLight.addListener(checkTheme);
	} catch (dontknow) {
	// not supported…
	}
	}
	}
	}());
	</script>
	<script>
	(function() {
	var theme = window.localStorage.getItem('theme');

	function revokeTheme() {
	if (!window.confirm('Do you want to stay with that theme?')) {
	window.localStorage.removeItem('theme');
	document.documentElement.dataset.theme = null;
	}
	}

	if (!theme) {
	if (window.confirm('This page offers a "dark" theme, you want to try it?')) {
	window.localStorage.setItem('theme', 'dark');
	document.documentElement.dataset.theme = 'dark';
	window.setTimeout(revokeTheme, 3000);
	} else {
	window.localStorage.setItem('theme', 'light');
	document.documentElement.dataset.theme = 'light';
	}
	}
	}())
	</script>
	<style>
	:root {
	--bg-color: hsla(0, 0%, 90%, 1);
	--text-color: hsla(0, 0%, 20%, 1);
	}
	*,
	*::before,
	*::after {
	box-sizing: border-box;
	}
	html {
	width: 100vw;
	height: 100vh;
	max-width: 100%;
	min-height: 100%;
	display: flex;
	overflow-x: hidden;
	margin: 0;
	align-items: center;
	justify-content: center;
	}

	body {
	background-color: var(--bg-color);
	color: var(--text-color);
	font-family: 'Big Shoulders Text', cursive;
	transition: color .2s ease-in, background-color .2s ease-out;
	}
	.mode::after {
	content: "light";
	}

	html[data-theme="dark"] {
	--bg-color: hsla(0, 0%, 20%, 1);
	--text-color: hsla(0,0%, 80%, 1);
	}
	html[data-theme="dark"] .mode::after {
	content: "dark";
	}
	</style>
	</head>
	<body>
	<section class="hero">
	<h1>Welcome to the <span class="mode"></span> mode</h1>
	</section>
	</body>
	</html>