feat: partition main canvas vertically (#6759)

Co-authored-by: Marcel Mraz <marcel.mraz@adacta-fintech.com>
Co-authored-by: dwelle <luzar.david@gmail.com>

src/scene/ShapeCache.ts

@@ -0,0 +1,61 @@
+import { Drawable } from "roughjs/bin/core";
+import { RoughGenerator } from "roughjs/bin/generator";
+import { ExcalidrawElement } from "../element/types";
+import { generateElementShape } from "../renderer/renderElement";
+
+type ElementShape = Drawable | Drawable[] | null;
+
+type ElementShapes = {
+  freedraw: Drawable | null;
+  arrow: Drawable[];
+  line: Drawable[];
+  text: null;
+  image: null;
+};
+
+export class ShapeCache {
+  private static rg = new RoughGenerator();
+  private static cache = new WeakMap<ExcalidrawElement, ElementShape>();
+
+  public static get = <T extends ExcalidrawElement>(element: T) => {
+    return ShapeCache.cache.get(
+      element,
+    ) as T["type"] extends keyof ElementShapes
+      ? ElementShapes[T["type"]] | undefined
+      : Drawable | null | 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
+   * return cached shape.
+   */
+  public static generateElementShape = <T extends ExcalidrawElement>(
+    element: T,
+  ) => {
+    const shape = generateElementShape(
+      element,
+      ShapeCache.rg,
+      /* so it prefers cache */ false,
+    ) as T["type"] extends keyof ElementShapes
+      ? ElementShapes[T["type"]]
+      : Drawable | null;
+
+    ShapeCache.cache.set(element, shape);
+
+    return shape;
+  };
+}