Tldraw/packages/tldraw/src/state/command/style/style.command.ts

import type { ShapeStyles, TLDrawCommand, Data } from '~types'
import { TLDR } from '~state/tldr'

export function style(data: Data, ids: string[], changes: Partial<ShapeStyles>): TLDrawCommand {
  const { currentPageId } = data.appState

  const shapeIdsToMutate = ids.flatMap((id) => TLDR.getDocumentBranch(data, id, currentPageId))

  const { before, after } = TLDR.mutateShapes(
    data,
    shapeIdsToMutate,
    (shape) => ({ style: { ...shape.style, ...changes } }),
    currentPageId
  )

  return {
    id: 'style',
    before: {
      document: {
        pages: {
          [currentPageId]: {
            shapes: before,
          },
        },
        pageStates: {
          [currentPageId]: {
            selectedIds: ids,
          },
        },
      },
      appState: {
        currentStyle: { ...data.appState.currentStyle },
      },
    },
    after: {
      document: {
        pages: {
          [currentPageId]: {
            shapes: after,
          },
        },
        pageStates: {
          [currentPageId]: {
            selectedIds: ids,
          },
        },
      },
      appState: {
        currentStyle: { ...data.appState.currentStyle, ...changes },
      },
    },
  }
}