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/element/src/selection.ts

@@ -169,25 +169,6 @@ export const isSomeElementSelected = (function () {
   return ret;
 })();
 
-/**
- * Returns common attribute (picked by `getAttribute` callback) of selected
- *  elements. If elements don't share the same value, returns `null`.
- */
-export const getCommonAttributeOfSelectedElements = <T>(
-  elements: readonly NonDeletedExcalidrawElement[],
-  appState: Pick<AppState, "selectedElementIds">,
-  getAttribute: (element: ExcalidrawElement) => T,
-): T | null => {
-  const attributes = Array.from(
-    new Set(
-      getSelectedElements(elements, appState).map((element) =>
-        getAttribute(element),
-      ),
-    ),
-  );
-  return attributes.length === 1 ? attributes[0] : null;
-};
-
 export const getSelectedElements = (
   elements: ElementsMapOrArray,
   appState: Pick<InteractiveCanvasAppState, "selectedElementIds">,

packages/element/src/typeChecks.ts

@@ -28,6 +28,7 @@ import type {
   PointBinding,
   FixedPointBinding,
   ExcalidrawFlowchartNodeElement,
+  ExcalidrawLinearElementSubType,
 } from "./types";
 
 export const isInitializedImageElement = (
@@ -356,3 +357,18 @@ export const isBounds = (box: unknown): box is Bounds =>
   typeof box[1] === "number" &&
   typeof box[2] === "number" &&
   typeof box[3] === "number";
+
+export const getLinearElementSubType = (
+  element: ExcalidrawLinearElement,
+): ExcalidrawLinearElementSubType => {
+  if (isSharpArrow(element)) {
+    return "sharpArrow";
+  }
+  if (isCurvedArrow(element)) {
+    return "curvedArrow";
+  }
+  if (isElbowArrow(element)) {
+    return "elbowArrow";
+  }
+  return "line";
+};

packages/element/src/types.ts

@@ -418,10 +418,12 @@ export type ElementsMapOrArray =
   | readonly ExcalidrawElement[]
   | Readonly<ElementsMap>;
 
-export type ConvertibleGenericTypes = "rectangle" | "diamond" | "ellipse";
-export type ConvertibleLinearTypes =
+export type ExcalidrawLinearElementSubType =
   | "line"
   | "sharpArrow"
   | "curvedArrow"
   | "elbowArrow";
+
+export type ConvertibleGenericTypes = "rectangle" | "diamond" | "ellipse";
+export type ConvertibleLinearTypes = ExcalidrawLinearElementSubType;
 export type ConvertibleTypes = ConvertibleGenericTypes | ConvertibleLinearTypes;