refactor: make element type conversion more generic (#9504)

* feat: add `reduceToCommonValue()` & improve opacity slider

* feat: generalize and simplify type conversion cache

* refactor: change cache from atoms to Map

* feat: always attempt to reuse original fontSize when converting generic types

packages/common/src/utils.test.ts

@@ -0,0 +1,82 @@
+import {
+  isTransparent,
+  mapFind,
+  reduceToCommonValue,
+} from "@excalidraw/common";
+
+describe("@excalidraw/common/utils", () => {
+  describe("isTransparent()", () => {
+    it("should return true when color is rgb transparent", () => {
+      expect(isTransparent("#ff00")).toEqual(true);
+      expect(isTransparent("#fff00000")).toEqual(true);
+      expect(isTransparent("transparent")).toEqual(true);
+    });
+
+    it("should return false when color is not transparent", () => {
+      expect(isTransparent("#ced4da")).toEqual(false);
+    });
+  });
+
+  describe("reduceToCommonValue()", () => {
+    it("should return the common value when all values are the same", () => {
+      expect(reduceToCommonValue([1, 1])).toEqual(1);
+      expect(reduceToCommonValue([0, 0])).toEqual(0);
+      expect(reduceToCommonValue(["a", "a"])).toEqual("a");
+      expect(reduceToCommonValue(new Set([1]))).toEqual(1);
+      expect(reduceToCommonValue([""])).toEqual("");
+      expect(reduceToCommonValue([0])).toEqual(0);
+
+      const o = {};
+      expect(reduceToCommonValue([o, o])).toEqual(o);
+
+      expect(
+        reduceToCommonValue([{ a: 1 }, { a: 1, b: 2 }], (o) => o.a),
+      ).toEqual(1);
+      expect(
+        reduceToCommonValue(new Set([{ a: 1 }, { a: 1, b: 2 }]), (o) => o.a),
+      ).toEqual(1);
+    });
+
+    it("should return `null` when values are different", () => {
+      expect(reduceToCommonValue([1, 2, 3])).toEqual(null);
+      expect(reduceToCommonValue(new Set([1, 2]))).toEqual(null);
+      expect(reduceToCommonValue([{ a: 1 }, { a: 2 }], (o) => o.a)).toEqual(
+        null,
+      );
+    });
+
+    it("should return `null` when some values are nullable", () => {
+      expect(reduceToCommonValue([1, null, 1])).toEqual(null);
+      expect(reduceToCommonValue([null, 1])).toEqual(null);
+      expect(reduceToCommonValue([1, undefined])).toEqual(null);
+      expect(reduceToCommonValue([undefined, 1])).toEqual(null);
+      expect(reduceToCommonValue([null])).toEqual(null);
+      expect(reduceToCommonValue([undefined])).toEqual(null);
+      expect(reduceToCommonValue([])).toEqual(null);
+    });
+  });
+
+  describe("mapFind()", () => {
+    it("should return the first mapped non-null element", () => {
+      {
+        let counter = 0;
+
+        const result = mapFind(["a", "b", "c"], (value) => {
+          counter++;
+          return value === "b" ? 42 : null;
+        });
+        expect(result).toEqual(42);
+        expect(counter).toBe(2);
+      }
+
+      expect(mapFind([1, 2], (value) => value * 0)).toBe(0);
+      expect(mapFind([1, 2], () => false)).toBe(false);
+      expect(mapFind([1, 2], () => "")).toBe("");
+    });
+
+    it("should return undefined if no mapped element is found", () => {
+      expect(mapFind([1, 2], () => undefined)).toBe(undefined);
+      expect(mapFind([1, 2], () => null)).toBe(undefined);
+    });
+  });
+});

packages/common/src/utils.ts

@@ -544,6 +544,20 @@ export const findLastIndex = <T>(
   return -1;
 };
 
+/** returns the first non-null mapped value */
+export const mapFind = <T, K>(
+  collection: readonly T[],
+  iteratee: (value: T, index: number) => K | undefined | null,
+): K | undefined => {
+  for (let idx = 0; idx < collection.length; idx++) {
+    const result = iteratee(collection[idx], idx);
+    if (result != null) {
+      return result;
+    }
+  }
+  return undefined;
+};
+
 export const isTransparent = (color: string) => {
   const isRGBTransparent = color.length === 5 && color.substr(4, 1) === "0";
   const isRRGGBBTransparent = color.length === 9 && color.substr(7, 2) === "00";
@@ -1244,11 +1258,39 @@ export const isReadonlyArray = (value?: any): value is readonly any[] => {
 };
 
 export const sizeOf = (
-  value: readonly number[] | Readonly<Map<any, any>> | Record<any, any>,
+  value:
+    | readonly unknown[]
+    | Readonly<Map<string, unknown>>
+    | Readonly<Record<string, unknown>>
+    | ReadonlySet<unknown>,
 ): number => {
   return isReadonlyArray(value)
     ? value.length
-    : value instanceof Map
+    : value instanceof Map || value instanceof Set
     ? value.size
     : Object.keys(value).length;
 };
+
+export const reduceToCommonValue = <T, R = T>(
+  collection: readonly T[] | ReadonlySet<T>,
+  getValue?: (item: T) => R,
+): R | null => {
+  if (sizeOf(collection) === 0) {
+    return null;
+  }
+
+  const valueExtractor = getValue || ((item: T) => item as unknown as R);
+
+  let commonValue: R | null = null;
+
+  for (const item of collection) {
+    const value = valueExtractor(item);
+    if ((commonValue === null || commonValue === value) && value != null) {
+      commonValue = value;
+    } else {
+      return null;
+    }
+  }
+
+  return commonValue;
+};