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);
+    });
+  });
+});