excalidraw/src/element/textWysiwyg.tsx

import { KEYS } from "../keys";
import { selectNode } from "../utils";

function trimText(text: string) {
  // whitespace only → trim all because we'd end up inserting invisible element
  if (!text.trim()) {
    return "";
  }
  // replace leading/trailing newlines (only) otherwise it messes up bounding
  //  box calculation (there's also a bug in FF which inserts trailing newline
  //  for multiline texts)
  return text.replace(/^\n+|\n+$/g, "");
}

type TextWysiwygParams = {
  initText: string;
  x: number;
  y: number;
  strokeColor: string;
  font: string;
  opacity: number;
  zoom: number;
  angle: number;
  onSubmit: (text: string) => void;
  onCancel: () => void;
};

export function textWysiwyg({
  initText,
  x,
  y,
  strokeColor,
  font,
  opacity,
  zoom,
  angle,
  onSubmit,
  onCancel,
}: TextWysiwygParams) {
  const editable = document.createElement("div");
  try {
    editable.contentEditable = "plaintext-only";
  } catch {
    editable.contentEditable = "true";
  }
  editable.dir = "auto";
  editable.tabIndex = 0;
  editable.innerText = initText;
  editable.dataset.type = "wysiwyg";

  const degree = (180 * angle) / Math.PI;

  Object.assign(editable.style, {
    color: strokeColor,
    position: "fixed",
    opacity: opacity / 100,
    top: `${y}px`,
    left: `${x}px`,
    transform: `translate(-50%, -50%) scale(${zoom}) rotate(${degree}deg)`,
    textAlign: "left",
    display: "inline-block",
    font: font,
    padding: "4px",
    // This needs to have "1px solid" otherwise the carret doesn't show up
    // the first time on Safari and Chrome!
    outline: "1px solid transparent",
    whiteSpace: "nowrap",
    minHeight: "1em",
    backfaceVisibility: "hidden",
  });

  editable.onpaste = (ev) => {
    try {
      const selection = window.getSelection();
      if (!selection?.rangeCount) {
        return;
      }
      selection.deleteFromDocument();

      const text = ev.clipboardData!.getData("text").replace(/\r\n?/g, "\n");

      const span = document.createElement("span");
      span.innerText = text;
      const range = selection.getRangeAt(0);
      range.insertNode(span);

      // deselect
      window.getSelection()!.removeAllRanges();
      range.setStart(span, span.childNodes.length);
      range.setEnd(span, span.childNodes.length);
      selection.addRange(range);

      ev.preventDefault();
    } catch (error) {
      console.error(error);
    }
  };

  editable.onkeydown = (ev) => {
    if (ev.key === KEYS.ESCAPE) {
      ev.preventDefault();
      handleSubmit();
    }
    if (ev.key === KEYS.ENTER && !ev.shiftKey) {
      ev.stopPropagation();
    }
  };
  editable.onblur = handleSubmit;

  function stopEvent(ev: Event) {
    ev.stopPropagation();
  }

  function handleSubmit() {
    if (editable.innerText) {
      onSubmit(trimText(editable.innerText));
    } else {
      onCancel();
    }
    cleanup();
  }

  function cleanup() {
    editable.onblur = null;
    editable.onkeydown = null;
    editable.onpaste = null;
    window.removeEventListener("wheel", stopEvent, true);
    document.body.removeChild(editable);
  }

  window.addEventListener("wheel", stopEvent, true);
  document.body.appendChild(editable);
  editable.focus();
  selectNode(editable);
}