Add automatic text direction detection + Right to Left Capbilities

[Karlee Wong (KarleeWong)]

Summary

Adds opt-in automatic text direction detection based on the first strong directional character in the active block.

Changes

• Update setModelDirection to:
  • Combine paragraph text segments.
  • Ignore leading numbers, whitespace, and punctuation.
  • Determine direction from the first letter, LTR mark, or RTL mark.
  • Default to LTR when no strong directional character exists.
• Export setModelDirection for model-level use.
• Add AutoDirectionPlugin.
  • Handles regular insertText input.
  • Handles compositionEnd for IME keyboards.
  • Updates direction without invoking the public API or focusing the editor.
• Export the plugin from roosterjs-content-model-plugins.
• Register the plugin in the RoosterJS demo.
• Add model and plugin unit tests.

Behavior

• שלום English uses RTL.
• Hello שלום uses LTR.
• 123 مرحبا uses RTL because leading numbers and punctuation are ignored.
• Content without a strong directional character defaults to LTR.
• Existing editors are unchanged unless AutoDirectionPlugin is registered.

Video

Recording.2026-08-25.115834.mp4

[Jiuqing Song (JiuqingSong)]

Please fix tests

[Karlee Wong (KarleeWong)]

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