ui/component/common/wait-until-on-page.jsx

@@ -2,7 +2,7 @@
 import React from 'react';
 import debounce from 'util/debounce';
 
-const DEBOUNCE_SCROLL_HANDLER_MS = 25;
+const DEBOUNCE_SCROLL_HANDLER_MS = 50;
 
 type Props = {
   children: any,
@@ -14,12 +14,13 @@ export default function WaitUntilOnPage(props: Props) {
   const ref = React.useRef();
   const [shouldRender, setShouldRender] = React.useState(false);
 
-  React.useEffect(() => {
-    const handleDisplayingRef = debounce((e) => {
+  const shouldElementRender = React.useCallback((ref) => {
     const element = ref && ref.current;
     if (element) {
       const bounding = element.getBoundingClientRect();
       if (
+        bounding.width > 0 &&
+        bounding.height > 0 &&
         bounding.bottom >= 0 &&
         bounding.right >= 0 &&
         // $FlowFixMe
@@ -27,20 +28,34 @@ export default function WaitUntilOnPage(props: Props) {
         // $FlowFixMe
         bounding.left <= (window.innerWidth || document.documentElement.clientWidth)
       ) {
+        return true;
+      }
+    }
+    return false;
+  }, []);
+
+  // Handles "element is already in viewport when mounted".
+  React.useEffect(() => {
+    setTimeout(() => {
+      if (!shouldRender && shouldElementRender(ref)) {
         setShouldRender(true);
       }
-      }
+    }, 500);
+  }, []); // eslint-disable-line react-hooks/exhaustive-deps
 
-      if (element && !shouldRender) {
-        window.addEventListener('scroll', handleDisplayingRef);
-        return () => window.removeEventListener('scroll', handleDisplayingRef);
+  // Handles "element scrolled into viewport".
+  React.useEffect(() => {
+    const handleDisplayingRef = debounce(() => {
+      if (shouldElementRender(ref)) {
+        setShouldRender(true);
       }
     }, DEBOUNCE_SCROLL_HANDLER_MS);
 
-    if (ref) {
-      handleDisplayingRef();
+    if (ref && ref.current && !shouldRender) {
+      window.addEventListener('scroll', handleDisplayingRef);
+      return () => window.removeEventListener('scroll', handleDisplayingRef);
     }
-  }, [ref, setShouldRender, shouldRender]);
+  }, [ref, setShouldRender, shouldRender, shouldElementRender]);
 
   const render = props.skipWait || shouldRender;