Fix flashing white when dark theme is enabled (#1176)

Load the theme code as fast as possible to prevent flashing the light theme before fetching and applying the dark theme from the URL or localstorage.
tabler · Aug 10, 2022 · c4a6a86 · c4a6a86 · vercel · Aug 10, 2022
1 parent baa9912
commit c4a6a86
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Showing 4 changed files with 33 additions and 20 deletions.
diff --git a/gulpfile.js b/gulpfile.js
@@ -287,6 +287,10 @@ gulp.task('js-demo', () => {
 	return compileJs('demo')
 })
 
+gulp.task('js-demo-theme', () => {
+	 return compileJs('demo-theme')
+})
+
 /**
  * Compile JS module files to dist directory
  */
@@ -420,7 +424,7 @@ gulp.task('build-critical', (cb) => {
  */
 gulp.task('watch', (cb) => {
 	gulp.watch('./src/scss/**/*.scss', gulp.series('sass'))
-	gulp.watch('./src/js/**/*.js', gulp.parallel('js', 'mjs', 'js-demo'))
+	gulp.watch('./src/js/**/*.js', gulp.parallel('js', 'mjs', gulp.parallel('js-demo', 'js-demo-theme')))
 	cb()
 })
 
@@ -520,8 +524,8 @@ gulp.task('add-banner', () => {
 
 gulp.task('clean', gulp.series('clean-dirs', 'clean-jekyll'))
 
-gulp.task('start', gulp.series('clean', 'sass', 'js', 'js-demo', 'mjs', 'build-jekyll', gulp.parallel('watch-jekyll', 'watch', 'browser-sync')))
+gulp.task('start', gulp.series('clean', 'sass', 'js', gulp.parallel('js-demo', 'js-demo-theme'), 'mjs', 'build-jekyll', gulp.parallel('watch-jekyll', 'watch', 'browser-sync')))
 
-gulp.task('build-core', gulp.series('build-on', 'clean', 'sass', 'css-rtl', 'css-minify', 'js', 'js-demo', 'mjs', 'copy-images', 'copy-libs', 'add-banner'))
+gulp.task('build-core', gulp.series('build-on', 'clean', 'sass', 'css-rtl', 'css-minify', 'js', gulp.parallel('js-demo', 'js-demo-theme'), 'mjs', 'copy-images', 'copy-libs', 'add-banner'))
 gulp.task('build-demo', gulp.series('build-on', 'build-jekyll', 'copy-static', 'copy-dist', 'build-cleanup', 'build-purgecss'/*, 'build-critical'*/))
 gulp.task('build', gulp.series('build-core', 'build-demo'))
diff --git a/src/js/demo-theme.js b/src/js/demo-theme.js
@@ -0,0 +1,25 @@
+/**
+ * demo-theme is specifically loaded right after the body and not deferred
+ * to ensure we switch to the chosen dark/light theme as fast as possible.
+ * This will prevent any flashes of the light theme (default) before switching.
+ */
+
+const themeStorageKey = 'tablerTheme'
+const defaultTheme = 'light'
+let selectedTheme
+
+// https://stackoverflow.com/a/901144
+const params = new Proxy(new URLSearchParams(window.location.search), {
+	 get: (searchParams, prop) => searchParams.get(prop),
+});
+
+if (!!params.theme) {
+	 localStorage.setItem(themeStorageKey, params.theme)
+	 selectedTheme = params.theme
+} else {
+	 const storedTheme = localStorage.getItem(themeStorageKey)
+	 selectedTheme = storedTheme ? storedTheme : defaultTheme
+}
+
+document.body.classList.remove('theme-dark', 'theme-light');
+document.body.classList.add(`theme-${selectedTheme}`);
diff --git a/src/js/demo.js b/src/js/demo.js
@@ -1,6 +1,5 @@
 // Setting items
 const items = {
-	'theme': { localStorage: 'tablerTheme', default: 'light' },
 	'menu-position': { localStorage: 'tablerMenuPosition', default: 'top' },
 	'menu-behavior': { localStorage: 'tablerMenuBehavior', default: 'sticky' },
 	'container-layout': { localStorage: 'tablerContainerLayout', default: 'boxed' }
@@ -44,16 +43,6 @@ const toggleFormControls = (form) => {
 	}
 }
 
-// Update body classes
-const updateBodyClasses = () => {
-	document.body.classList.remove('theme-dark', 'theme-light');
-	document.body.classList.add(`theme-${config.theme}`);
-
-	// for (const [key, params] of Object.entries(items)) {
-	// 	document.body.setAttribute(`data-${key}`, config[key]);
-	// }
-}
-
 // Submit form
 const submitForm = (form) => {
 	// Save data to localStorage
@@ -66,9 +55,6 @@ const submitForm = (form) => {
 		config[key] = value
 	}
 
-	// Update body classes
-	updateBodyClasses();
-
 	window.dispatchEvent(new Event('resize'));
 
 	(new bootstrap.Offcanvas(form)).hide()
@@ -78,9 +64,6 @@ const submitForm = (form) => {
 // Parse url
 parseUrl()
 
-// Update body classes
-updateBodyClasses();
-
 // Elements
 const form = document.querySelector('#offcanvasSettings')
 

diff --git a/src/pages/_layouts/base.html b/src/pages/_layouts/base.html
@@ -47,6 +47,7 @@
 
 {% assign layout-dark = page.layout-dark | default: site.layout-dark %}
 <body {% if layout.body-class or page.body-class %} class="{% if layout.body-class %} {{ layout.body-class }}{% endif %}{% if page.body-class %} {{ page.body-class }}{% endif %}"{% endif %}>
+<script src="{{ site.base }}/dist/js/demo-theme{% if jekyll.environment != 'development' %}.min{% endif %}.js{% if jekyll.environment == 'preview' %}?{{ site.time | date: '%s' }}{% endif %}"></script>
 
 	{{ content }}