From 437f4b9ab9a9f5b5a0e9d73ed3174e6f063f823e Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 29 May 2026 02:00:41 +0000
Subject: [PATCH] Perf: Defer widget-schema prefetch AJAX to
 requestIdleCallback
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Phase 5 of the perf series.

requestWidgetsConfig fetches ~394 KB of widget control schemas for widget types
NOT used on the page (in-page widgets already have their schemas in the boot
config). Currently fires synchronously during initEditor, so the response
parse + 394 KB jQuery.extend(true,{},...) deep-merge into widgetsCache races
with initial canvas render on the main thread.

This defers the entire request body + send + response processing into
requestIdleCallback (with a 3s timeout safety net, and setTimeout(0) fallback
for browsers without rIC). The only thing waiting on it is the panel-loading
spinner via panel/state-ready — the canvas is interactive immediately.

Gated by the existing e_memoize_active_controls experiment.
---
 assets/dev/js/editor/editor-base.js | 33 ++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/assets/dev/js/editor/editor-base.js b/assets/dev/js/editor/editor-base.js
index 567e9910da6d..9cb7cf403be1 100644
--- a/assets/dev/js/editor/editor-base.js
+++ b/assets/dev/js/editor/editor-base.js
@@ -1137,15 +1137,16 @@ export default class EditorBase extends Marionette.Application {
 	}
 
 	requestWidgetsConfig() {
-		const excludeWidgets = {};
+		const run = () => {
+			const excludeWidgets = {};
 
-		jQuery.each( this.widgetsCache, ( widgetName, widgetConfig ) => {
-			if ( widgetConfig.controls ) {
-				excludeWidgets[ widgetName ] = true;
-			}
-		} );
+			jQuery.each( this.widgetsCache, ( widgetName, widgetConfig ) => {
+				if ( widgetConfig.controls ) {
+					excludeWidgets[ widgetName ] = true;
+				}
+			} );
 
-		elementorCommon.ajax.addRequest( 'get_widgets_config', {
+			elementorCommon.ajax.addRequest( 'get_widgets_config', {
 			data: {
 				exclude: excludeWidgets,
 			},
@@ -1166,7 +1167,23 @@ export default class EditorBase extends Marionette.Application {
 					} );
 				}
 			},
-		} );
+			} );
+		};
+
+		// Defer the schema-prefetch (request body + ~394 KB JSON response parse + the
+		// per-widget deep-merge in addWidgetsCache) into idle time so it does not race
+		// with the initial canvas render. The data is only needed when the user opens
+		// the widget panel to add a new element; in-page widgets already have their
+		// schemas in the boot config. Falls back to setTimeout where requestIdleCallback
+		// is unavailable (Safari pre-15.4).
+		const useDefer = elementorCommon?.config?.experimentalFeatures?.e_memoize_active_controls;
+		if ( useDefer && 'function' === typeof window.requestIdleCallback ) {
+			window.requestIdleCallback( run, { timeout: 3000 } );
+		} else if ( useDefer ) {
+			setTimeout( run, 0 );
+		} else {
+			run();
+		}
 	}
 
 	async refreshWidgets() {