Text Direction Auto Plugin

The TextDirectionAutoPlugin registers three transaction middlewares that keep block-level dir attributes in sync with content changes. It is a headless plugin — no toolbar, no commands, no keymaps — purely middleware.

It requires the Text Direction plugin to be registered first. The framework enforces this via dependencies and will throw with a descriptive error if you register TextDirectionAutoPlugin without it.

Usage

import { TextDirectionPlugin } from '@notectl/core/plugins/text-direction';
import { TextDirectionAutoPlugin } from '@notectl/core/plugins/text-direction-auto';

[
  new TextDirectionPlugin(),
  new TextDirectionAutoPlugin(),
]

Configuration

Each middleware can be disabled individually:

interface TextDirectionAutoConfig {
  /** Auto-detect direction on insertText / deleteText. Default: true. */
  readonly autoDetect?: boolean;
  /** Inherit direction from siblings on insertNode. Default: true. */
  readonly inherit?: boolean;
  /** Preserve direction across setBlockType (e.g. paragraph → heading). Default: true. */
  readonly preserve?: boolean;
}

The Three Middlewares

Auto-Detect

When text is inserted or deleted in a block with dir="auto", the plugin detects the dominant direction from the first strong directional character (using Unicode Script property escapes) and updates the block’s dir. Supports 20+ RTL scripts including Arabic, Hebrew, Syriac, Thaana, N’Ko, Adlam, Hanifi Rohingya, and historic scripts.

// User types Arabic into an empty paragraph (dir="auto")
// → middleware detects RTL and sets dir="rtl" on the same transaction

Inherit Direction

When a new block is inserted (e.g. via Enter, paste, or programmatic insertNode), the plugin first tries to detect direction from the inserted block’s text content; failing that, it inherits the dir from the nearest sibling. This produces a seamless writing experience in RTL documents — pressing Enter in an RTL paragraph yields another RTL paragraph.

Preserve Direction

When another plugin replaces a block’s attributes via setBlockType (e.g. paragraph → heading via the heading dropdown), the existing dir would normally be lost because setBlockType overrides the entire attrs object. This middleware copies the previous dir (when it was non-'auto') into the new attrs, so the user’s direction choice survives the type change.

Hard Dependency on TextDirectionPlugin

This plugin declares dependencies = ['text-direction']. The framework’s plugin lifecycle:

• Refuses to start if TextDirectionPlugin is not registered, with the error Plugin "text-direction-auto" depends on "text-direction", which is not registered.
• Initializes TextDirectionPlugin first so its TextDirectionService (with directableTypes) is available when this plugin’s init() runs.

The middlewares mutate the dir attribute that TextDirectionPlugin patches into NodeSpecs; without that patch, setNodeAttr({ dir: ... }) would write an attribute the renderer ignores.

Accessibility

• Direction changes propagate to the rendered dir attribute, which assistive technology respects natively
• No new UI surface — accessibility is inherited from TextDirectionPlugin’s toolbar / keymap

Performance

The middlewares examine each step of every transaction. They short-circuit early for non-directable block types and never traverse the document beyond the affected block (and, for inherit-dir, immediate siblings).