fixed 打赏卡片逻辑修复

themes/Ying/assets/js/modules/floating-tools.js

@@ -33,41 +33,57 @@ window.initFloatingTools = function() {
             }
         }
 
-        // 1. Back to Top
+        // 1. Back to Top (Optimized with IntersectionObserver)
         var backToTopButton = document.getElementById('back-to-top');
         if (backToTopButton) {
-            var ticking = false;
-
-            function update() {
-                var btn = document.getElementById('back-to-top');
-                if (!btn) return;
-                
-                // Only show if NOT on homepage (redundant if container is hidden, but good for safety)
-                if (window.scrollY > 300) {
-                    if (!btn.classList.contains('show')) {
-                        btn.classList.add('show');
-                    }
-                } else {
-                    if (btn.classList.contains('show')) {
-                        btn.classList.remove('show');
-                    }
-                }
-                ticking = false;
+            
+            // Clean up old scroll handler if exists (from previous Pjax or version)
+            if (window.backToTopScrollHandler) {
+                window.removeEventListener('scroll', window.backToTopScrollHandler);
+                window.backToTopScrollHandler = null;
             }
 
-            // Global Scroll Handler (Singleton)
-            if (!window.backToTopScrollHandler) {
+            // Create or reuse sentinel for IntersectionObserver
+            var sentinelId = 'back-to-top-sentinel';
+            var sentinel = document.getElementById(sentinelId);
+            if (!sentinel) {
+                sentinel = document.createElement('div');
+                sentinel.id = sentinelId;
+                // Sentinel covers the top 300px. When it exits viewport, we show button.
+                sentinel.style.cssText = 'position: absolute; top: 0; left: 0; width: 1px; height: 300px; pointer-events: none; visibility: hidden; z-index: -9999;';
+                document.body.appendChild(sentinel);
+            }
+
+            if (window.IntersectionObserver) {
+                var observer = new IntersectionObserver(function(entries) {
+                    entries.forEach(function(entry) {
+                        if (!entry.isIntersecting) {
+                            // Sentinel is out of view (scrolled down past 300px)
+                            backToTopButton.classList.add('show');
+                        } else {
+                            // Sentinel is in view (near top)
+                            backToTopButton.classList.remove('show');
+                        }
+                    });
+                });
+                observer.observe(sentinel);
+            } else {
+                // Fallback for very old browsers
+                var ticking = false;
+                var update = function() {
+                    if (window.scrollY > 300) {
+                        backToTopButton.classList.add('show');
+                    } else {
+                        backToTopButton.classList.remove('show');
+                    }
+                    ticking = false;
+                };
                 window.backToTopScrollHandler = function() {
-                    // Performance Optimization: Check scroll less frequently? 
-                    // No, rAF is best. But we can add a check if the button is even in DOM/Visible?
-                    // But checking DOM layout is expensive.
-                    // Keep rAF but ensure 'update' is light.
                     if (!ticking) {
                         window.requestAnimationFrame(update);
                         ticking = true;
                     }
                 };
-                // Use passive listener to prevent scroll blocking
                 window.addEventListener('scroll', window.backToTopScrollHandler, { passive: true });
             }
 
@@ -78,9 +94,6 @@ window.initFloatingTools = function() {
                 backToTopButton = newBtn;
             }
 
-            // Initialize state immediately
-            update();
-
             backToTopButton.addEventListener('click', function(e) {
                 e.preventDefault();
                 window.scrollTo({