perf: improve rendering performance for Library (#6587)

* perf: improve rendering performance for Library

* fix: return onDrag and onToggle functionality to Library Items

* perf: cache exportToSvg output

* fix: lint warning

* fix: add onClick handler into LibraryUnit

* feat: better spinner

* fix: useCallback for getInsertedElements to fix linter error

* feat: different batch size when svgs are cached

* fix: library items alignment in row

* feat: skeleton instead of spinner

* fix: remove unused variables

* feat: use css vars instead of hadcoded colors

* feat: reverting skeleton, removing spinner

* cleanup and unrelated refactor

* change ROWS_RENDERED_PER_BATCH to 6

---------

Co-authored-by: dwelle <luzar.david@gmail.com>

src/hooks/useLibraryItemSvg.ts

@@ -0,0 +1,59 @@
+import { atom, useAtom } from "jotai";
+import { useEffect, useState } from "react";
+import { COLOR_PALETTE } from "../colors";
+import { exportToSvg } from "../packages/utils";
+import { LibraryItem } from "../types";
+
+export const libraryItemSvgsCache = atom<Map<LibraryItem["id"], SVGSVGElement>>(
+  new Map(),
+);
+
+const exportLibraryItemToSvg = async (elements: LibraryItem["elements"]) => {
+  return await exportToSvg({
+    elements,
+    appState: {
+      exportBackground: false,
+      viewBackgroundColor: COLOR_PALETTE.white,
+    },
+    files: null,
+  });
+};
+
+export const useLibraryItemSvg = (
+  id: LibraryItem["id"] | null,
+  elements: LibraryItem["elements"] | undefined,
+): SVGSVGElement | undefined => {
+  const [svgCache, setSvgCache] = useAtom(libraryItemSvgsCache);
+  const [svg, setSvg] = useState<SVGSVGElement>();
+
+  useEffect(() => {
+    if (elements) {
+      if (id) {
+        // Try to load cached svg
+        const cachedSvg = svgCache.get(id);
+
+        if (cachedSvg) {
+          setSvg(cachedSvg);
+        } else {
+          // When there is no svg in cache export it and save to cache
+          (async () => {
+            const exportedSvg = await exportLibraryItemToSvg(elements);
+
+            if (exportedSvg) {
+              setSvgCache(svgCache.set(id, exportedSvg));
+              setSvg(exportedSvg);
+            }
+          })();
+        }
+      } else {
+        // When we have no id (usualy selected items from canvas) just export the svg
+        (async () => {
+          const exportedSvg = await exportLibraryItemToSvg(elements);
+          setSvg(exportedSvg);
+        })();
+      }
+    }
+  }, [id, elements, svgCache, setSvgCache, setSvg]);
+
+  return svg;
+};