Restore scroll position on page refresh

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Co-Authored-By: Claude <noreply@anthropic.com>

app/RSpade/Core/Js/Rsx.js

@@ -664,6 +664,81 @@ class Rsx {
         // DO NOT use this in application code - use on_app_ready() phase instead
         // This event exists solely for debugging tools that need to run after full initialization
         Rsx.trigger('_debug_ready');
+
+        // Restore scroll position on page refresh
+        Rsx._restore_scroll_on_refresh();
+    }
+
+    /**
+     * Storage key for scroll position in sessionStorage
+     * @private
+     */
+    static _SCROLL_STORAGE_KEY = 'rsx_scroll_pos';
+
+    /**
+     * Save scroll position to sessionStorage on scroll (debounced)
+     * Called from scroll event listener set up in _restore_scroll_on_refresh
+     * @private
+     */
+    static _scroll_save_timeout = null;
+    static _save_scroll_position() {
+        // Debounce: cancel pending save and schedule fresh one
+        if (Rsx._scroll_save_timeout) {
+            clearTimeout(Rsx._scroll_save_timeout);
+        }
+
+        Rsx._scroll_save_timeout = setTimeout(() => {
+            const scroll_data = {
+                url: window.location.pathname + window.location.search,
+                x: window.scrollX,
+                y: window.scrollY
+            };
+            sessionStorage.setItem(Rsx._SCROLL_STORAGE_KEY, JSON.stringify(scroll_data));
+        }, 100); // 100ms debounce
+    }
+
+    /**
+     * Restore scroll position if this is a page refresh
+     * Uses Performance API to detect reload navigation type
+     * @private
+     */
+    static _restore_scroll_on_refresh() {
+        // Set up scroll listener to continuously save position
+        window.addEventListener('scroll', Rsx._save_scroll_position, { passive: true });
+
+        // Check if this is a page refresh using Performance API
+        const nav_entries = performance.getEntriesByType('navigation');
+        if (nav_entries.length === 0) return;
+
+        const nav_type = nav_entries[0].type;
+        if (nav_type !== 'reload') return;
+
+        // This is a refresh - try to restore scroll position
+        const stored = sessionStorage.getItem(Rsx._SCROLL_STORAGE_KEY);
+        if (!stored) return;
+
+        try {
+            const scroll_data = JSON.parse(stored);
+            const current_url = window.location.pathname + window.location.search;
+
+            // Only restore if URL matches
+            if (scroll_data.url !== current_url) return;
+
+            // Restore scroll position instantly
+            window.scrollTo({
+                left: scroll_data.x,
+                top: scroll_data.y,
+                behavior: 'instant'
+            });
+
+            console_debug('Rsx', `Restored scroll position on refresh: ${scroll_data.x}, ${scroll_data.y}`);
+
+            // Clear stored position after successful restore
+            sessionStorage.removeItem(Rsx._SCROLL_STORAGE_KEY);
+        } catch (e) {
+            // Invalid JSON or other error - ignore
+            sessionStorage.removeItem(Rsx._SCROLL_STORAGE_KEY);
+        }
     }
 
     /* Calling this stops the boot process. */