excalidraw/packages/excalidraw/actions/actionDecreaseFontSize.ts

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

import { register } from "./register";
import { changeFontSize, FONT_SIZE_RELATIVE_INCREASE_STEP } from "./utils";

export const actionDecreaseFontSize = register({
  name: "decreaseFontSize",
  trackEvent: false,
  perform: (elements, appState, value, app) => {
    return changeFontSize(elements, appState, app, (element) =>
      Math.round(
        // get previous value before relative increase (doesn't work fully
        // due to rounding and float precision issues)
        (1 / (1 + FONT_SIZE_RELATIVE_INCREASE_STEP)) * element.fontSize,
      ),
    );
  },
  keyTest: (event) => {
    return (
      event[KEYS.CTRL_OR_CMD] &&
      event.shiftKey &&
      // KEYS.COMMA needed for MacOS
      (event.key === KEYS.CHEVRON_LEFT || event.key === KEYS.COMMA)
    );
  },
});