refactor: separate elements logic into a standalone package (#9285)

packages/element/src/ShapeCache.ts

@@ -0,0 +1,95 @@
+import { RoughGenerator } from "roughjs/bin/generator";
+
+import { COLOR_PALETTE } from "@excalidraw/common";
+
+import type {
+  AppState,
+  EmbedsValidationStatus,
+} from "@excalidraw/excalidraw/types";
+import type {
+  ElementShape,
+  ElementShapes,
+} from "@excalidraw/excalidraw/scene/types";
+
+import { _generateElementShape } from "./Shape";
+
+import { elementWithCanvasCache } from "./renderElement";
+
+import type { ExcalidrawElement, ExcalidrawSelectionElement } from "./types";
+
+import type { Drawable } from "roughjs/bin/core";
+
+export class ShapeCache {
+  private static rg = new RoughGenerator();
+  private static cache = new WeakMap<ExcalidrawElement, ElementShape>();
+
+  /**
+   * Retrieves shape from cache if available. Use this only if shape
+   * is optional and you have a fallback in case it's not cached.
+   */
+  public static get = <T extends ExcalidrawElement>(element: T) => {
+    return ShapeCache.cache.get(
+      element,
+    ) as T["type"] extends keyof ElementShapes
+      ? ElementShapes[T["type"]] | undefined
+      : ElementShape | undefined;
+  };
+
+  public static set = <T extends ExcalidrawElement>(
+    element: T,
+    shape: T["type"] extends keyof ElementShapes
+      ? ElementShapes[T["type"]]
+      : Drawable,
+  ) => ShapeCache.cache.set(element, shape);
+
+  public static delete = (element: ExcalidrawElement) =>
+    ShapeCache.cache.delete(element);
+
+  public static destroy = () => {
+    ShapeCache.cache = new WeakMap();
+  };
+
+  /**
+   * Generates & caches shape for element if not already cached, otherwise
+   * returns cached shape.
+   */
+  public static generateElementShape = <
+    T extends Exclude<ExcalidrawElement, ExcalidrawSelectionElement>,
+  >(
+    element: T,
+    renderConfig: {
+      isExporting: boolean;
+      canvasBackgroundColor: AppState["viewBackgroundColor"];
+      embedsValidationStatus: EmbedsValidationStatus;
+    } | null,
+  ) => {
+    // when exporting, always regenerated to guarantee the latest shape
+    const cachedShape = renderConfig?.isExporting
+      ? undefined
+      : ShapeCache.get(element);
+
+    // `null` indicates no rc shape applicable for this element type,
+    // but it's considered a valid cache value (= do not regenerate)
+    if (cachedShape !== undefined) {
+      return cachedShape;
+    }
+
+    elementWithCanvasCache.delete(element);
+
+    const shape = _generateElementShape(
+      element,
+      ShapeCache.rg,
+      renderConfig || {
+        isExporting: false,
+        canvasBackgroundColor: COLOR_PALETTE.white,
+        embedsValidationStatus: null,
+      },
+    ) as T["type"] extends keyof ElementShapes
+      ? ElementShapes[T["type"]]
+      : Drawable | null;
+
+    ShapeCache.cache.set(element, shape);
+
+    return shape;
+  };
+}