excalidraw/src/actions/actionDuplicateSelection.tsx

import React from "react";
import { KEYS } from "../keys";
import { register } from "./register";
import { ExcalidrawElement } from "../element/types";
import { duplicateElement, getNonDeletedElements } from "../element";
import { isSomeElementSelected } from "../scene";
import { ToolButton } from "../components/ToolButton";
import { clone } from "../components/icons";
import { t } from "../i18n";
import { getShortcutKey } from "../utils";
import { LinearElementEditor } from "../element/linearElementEditor";
import { mutateElement } from "../element/mutateElement";

export const actionDuplicateSelection = register({
  name: "duplicateSelection",
  perform: (elements, appState) => {
    // duplicate point if selected while editing multi-point element
    if (appState.editingLinearElement) {
      const { activePointIndex, elementId } = appState.editingLinearElement;
      const element = LinearElementEditor.getElement(elementId);
      if (!element || activePointIndex === null) {
        return false;
      }
      const { points } = element;
      const selectedPoint = points[activePointIndex];
      const nextPoint = points[activePointIndex + 1];
      mutateElement(element, {
        points: [
          ...points.slice(0, activePointIndex + 1),
          nextPoint
            ? [
                (selectedPoint[0] + nextPoint[0]) / 2,
                (selectedPoint[1] + nextPoint[1]) / 2,
              ]
            : [selectedPoint[0] + 30, selectedPoint[1] + 30],
          ...points.slice(activePointIndex + 1),
        ],
      });
      return {
        appState: {
          ...appState,
          editingLinearElement: {
            ...appState.editingLinearElement,
            activePointIndex: activePointIndex + 1,
          },
        },
        elements,
        commitToHistory: true,
      };
    }

    const groupIdMap = new Map();
    return {
      appState,
      elements: elements.reduce(
        (acc: Array<ExcalidrawElement>, element: ExcalidrawElement) => {
          if (appState.selectedElementIds[element.id]) {
            const newElement = duplicateElement(
              appState.editingGroupId,
              groupIdMap,
              element,
              {
                x: element.x + 10,
                y: element.y + 10,
              },
            );
            appState.selectedElementIds[newElement.id] = true;
            delete appState.selectedElementIds[element.id];
            return acc.concat([element, newElement]);
          }
          return acc.concat(element);
        },
        [],
      ),
      commitToHistory: true,
    };
  },
  contextItemLabel: "labels.duplicateSelection",
  keyTest: (event) => event[KEYS.CTRL_OR_CMD] && event.key === "d",
  PanelComponent: ({ elements, appState, updateData }) => (
    <ToolButton
      type="button"
      icon={clone}
      title={`${t("labels.duplicateSelection")} — ${getShortcutKey(
        "CtrlOrCmd+D",
      )}`}
      aria-label={t("labels.duplicateSelection")}
      onClick={() => updateData(null)}
      visible={isSomeElementSelected(getNonDeletedElements(elements), appState)}
    />
  ),
});