first commit

wp-content/themes/twentytwentyone/assets/js/editor-dark-mode-support.js

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+/* global twentytwentyoneIsDarkMode, setTimeout */
+
+// Check the color scheme preference and inject the classes if necessary.
+if ( document.body.classList.contains( 'twentytwentyone-supports-dark-theme' ) ) {
+	twentytwentyoneDarkModeEditorInit();
+}
+
+/**
+ * Once the editor loads, add the dark mode class.
+ *
+ * Wait for the editor to load by periodically checking for an element, then we add the classes.
+ *
+ * @since 1.0.0
+ *
+ * @param {number} attempt Track the number of tries
+ * @return {void}
+ */
+function twentytwentyoneDarkModeEditorInit( attempt ) {
+	var container = document.querySelector( '.block-editor__typewriter' ),
+		maxAttempts = 8;
+
+	// Set the initial attempt if it's undefined.
+	attempt = attempt || 0;
+
+	if ( twentytwentyoneIsDarkMode() ) {
+		if ( null === container ) {
+			// Try again.
+			if ( attempt < maxAttempts ) {
+				setTimeout(
+					function() {
+						twentytwentyoneDarkModeEditorInit( attempt + 1 );
+					},
+					// Double the delay, give the server some time to breathe.
+					25 * Math.pow( 2, attempt )
+				);
+			}
+			return;
+		}
+
+		document.body.classList.add( 'is-dark-theme' );
+		document.documentElement.classList.add( 'is-dark-theme' );
+		container.classList.add( 'is-dark-theme' );
+	}
+}