WIP: optimize resize performance

packages/base/data/list-table-v2.vue

@@ -123,6 +123,10 @@ const estimatedHeaderHeight = ref<number | undefined>(undefined);
 let miniTableResizeObserver: ResizeObserver | null = null;
 let lastMiniTableHeight = 0;
 
+// Track if table is visible in viewport - only probe when visible
+const isInViewport = ref(false);
+let viewportObserver: IntersectionObserver | null = null;
+
 // Header height constant
 
 type TimestampValue =
@@ -285,9 +289,10 @@ function estimateTableRowHeight() {
 // Observe miniTableRef instead of myTableRef - only re-probe if mini-table's rendered height changes
 // This avoids unnecessary re-probing during window resize when container width changes but row heights stay same
 onMounted(() => {
-  // Resize handler - only re-probe if the mini-table's actual height changed
+  // Resize handler - only re-probe if the mini-table's actual height changed AND table is visible
   const handleResize = lodash.debounce(async () => {
-    if (!shouldUseProbeRow.value || miniTableData.value.length === 0) {
+    // Skip if not using probe, no data, or not visible in viewport
+    if (!shouldUseProbeRow.value || miniTableData.value.length === 0 || !isInViewport.value) {
       return;
     }
 
@@ -315,16 +320,43 @@ onMounted(() => {
       estimatedRowHeight.value = newRow;
       estimatedHeaderHeight.value = newHeader;
     });
-  }, 200);
+  }, 50);
 
-  // Observe miniTableRef for height changes
+  // ResizeObserver for mini-table height changes
-  // The mini-table's height only changes when column widths cause text to wrap
-  // During typical window resize with fixed-height content, height stays same → no re-probe
   miniTableResizeObserver = new ResizeObserver(() => {
     handleResize();
   });
 
-  if (miniTableRef.value) {
+  // IntersectionObserver to track viewport visibility
+  // Only attach ResizeObserver when table is visible, detach when off-screen
+  // This saves CPU for tables scrolled out of view
+  viewportObserver = new IntersectionObserver(
+    (entries) => {
+      const entry = entries[0];
+      isInViewport.value = entry.isIntersecting;
+
+      if (entry.isIntersecting) {
+        // Table became visible - reconnect ResizeObserver
+        if (miniTableRef.value && miniTableResizeObserver) {
+          miniTableResizeObserver.observe(miniTableRef.value);
+        }
+      } else {
+        // Table went off-screen - disconnect ResizeObserver to save CPU
+        // Heights are cached, so no need to keep observing
+        if (miniTableResizeObserver) {
+          miniTableResizeObserver.disconnect();
+        }
+      }
+    },
+    { threshold: 0 } // Trigger as soon as any part is visible
+  );
+
+  if (myTableRef.value) {
+    viewportObserver.observe(myTableRef.value);
+  }
+
+  // Initial observation of mini-table if already in viewport
+  if (miniTableRef.value && isInViewport.value && miniTableResizeObserver) {
     miniTableResizeObserver.observe(miniTableRef.value);
   }
 });
@@ -335,6 +367,10 @@ onUnmounted(() => {
     miniTableResizeObserver.disconnect();
     miniTableResizeObserver = null;
   }
+  if (viewportObserver) {
+    viewportObserver.disconnect();
+    viewportObserver = null;
+  }
 });
 
 const containerStyle = computed(() => {