chore: virtualization ish behaviour for issue layouts (#3538)

* Virtualization like core changes with intersection observer

* Virtualization like changes for spreadsheet

* Virtualization like changes for list

* Virtualization like changes for kanban

* add logic to render all the issues at once

* revert back the changes for list to follow the old pattern of grouping

* fix column shadow in spreadsheet for rendering rows

* fix constant draggable height while dragging and rendering blocks in kanban

* fix height glitch while rendered rows adjust to default height

* remove loading animation for issue layouts

* reduce requestIdleCallback timer to 300ms

* remove logic for index tarcking to force render as the same effect seems to be achieved by removing requestIdleCallback

* Fix Kanban droppable height

* fix spreadsheet sub issue loading

* force change in reference to re render the render if visible component when the order of list changes

* add comments and minor changes

web/components/core/render-if-visible-HOC.tsx

@@ -0,0 +1,80 @@
+import { cn } from "helpers/common.helper";
+import React, { useState, useRef, useEffect, ReactNode, MutableRefObject } from "react";
+
+type Props = {
+  defaultHeight?: string;
+  verticalOffset?: number;
+  horizonatlOffset?: number;
+  root?: MutableRefObject<HTMLElement | null>;
+  children: ReactNode;
+  as?: keyof JSX.IntrinsicElements;
+  classNames?: string;
+  alwaysRender?: boolean;
+  placeholderChildren?: ReactNode;
+  pauseHeightUpdateWhileRendering?: boolean;
+  changingReference?: any;
+};
+
+const RenderIfVisible: React.FC<Props> = (props) => {
+  const {
+    defaultHeight = "300px",
+    root,
+    verticalOffset = 50,
+    horizonatlOffset = 0,
+    as = "div",
+    children,
+    classNames = "",
+    alwaysRender = false, //render the children even if it is not visble in root
+    placeholderChildren = null, //placeholder children
+    pauseHeightUpdateWhileRendering = false, //while this is true the height of the blocks are maintained
+    changingReference, //This is to force render when this reference is changed
+  } = props;
+  const [shouldVisible, setShouldVisible] = useState<boolean>(alwaysRender);
+  const placeholderHeight = useRef<string>(defaultHeight);
+  const intersectionRef = useRef<HTMLElement | null>(null);
+
+  const isVisible = alwaysRender || shouldVisible;
+
+  // Set visibility with intersection observer
+  useEffect(() => {
+    if (intersectionRef.current) {
+      const observer = new IntersectionObserver(
+        (entries) => {
+          if (typeof window !== undefined && window.requestIdleCallback) {
+            window.requestIdleCallback(() => setShouldVisible(entries[0].isIntersecting), {
+              timeout: 300,
+            });
+          } else {
+            setShouldVisible(entries[0].isIntersecting);
+          }
+        },
+        {
+          root: root?.current,
+          rootMargin: `${verticalOffset}% ${horizonatlOffset}% ${verticalOffset}% ${horizonatlOffset}%`,
+        }
+      );
+      observer.observe(intersectionRef.current);
+      return () => {
+        if (intersectionRef.current) {
+          observer.unobserve(intersectionRef.current);
+        }
+      };
+    }
+  }, [root?.current, intersectionRef, children, changingReference]);
+
+  //Set height after render
+  useEffect(() => {
+    if (intersectionRef.current && isVisible) {
+      placeholderHeight.current = `${intersectionRef.current.offsetHeight}px`;
+    }
+  }, [isVisible, intersectionRef, alwaysRender, pauseHeightUpdateWhileRendering]);
+
+  const child = isVisible ? <>{children}</> : placeholderChildren;
+  const style =
+    isVisible && !pauseHeightUpdateWhileRendering ? {} : { height: placeholderHeight.current, width: "100%" };
+  const className = isVisible ? classNames : cn(classNames, "bg-custom-background-80");
+
+  return React.createElement(as, { ref: intersectionRef, style, className }, child);
+};
+
+export default RenderIfVisible;