macOS/iTerm2: Hebrew (RTL) text renders reversed inside herdr panes #5118

Activity

1. akbash-bot

   added

   triagedScreened; left open for investigation or maintainer judgment. Not proof of a bug or reproduction.Screened; left open for investigation or maintainer judgment. Not proof of a bug or reproduction.

   p2valid narrow or ordinary defect with limited impact or a practical workaroundvalid narrow or ordinary defect with limited impact or a practical workaround

   macosaffects macOS-specific behavioraffects macOS-specific behavior

   renderingterminal emulation, reflow, layout, graphics, or output renderingterminal emulation, reflow, layout, graphics, or output rendering

   maintainer-neededrequires maintainer judgment or maintainer-only reproductionrequires maintainer judgment or maintainer-only reproduction

   on Oct 9, 2026
2. barnuri commented on Oct 23, 2026

   

   barnuri

   on Oct 23, 2026

   More actions

   I implemented this as an opt-in pane display transform in herdr itself, so Hebrew/Arabic render correctly in every outer terminal (VS Code, Ghostty, iTerm), not just ones with BiDi support.

   • Config: [ui] pane_transforms = ["bidi"] (default off, live reload)
   • Uses the unicode-bidi crate (UAX fix: support IME input for Chinese and other UTF-8 characters #9). ASCII rows are untouched; a full screen of Hebrew adds about 0.2 ms per frame.
   • Copy stays in logical order, and mouse clicks are mapped back to logical columns.
   • Before/after screenshots and tests are in the PR.

   PR: #5500 (mirror: barnuri#1)

   The PR gate may auto-close it because I'm not on APPROVED_CONTRIBUTORS. If a maintainer wants this, please reopen it or add me to the list.
3. MMTE commented on Oct 25, 2026

   

   MMTE

   on Oct 25, 2026

   More actions

   Confirming this reproduces on Persian too, with a byte-level detail that may help the investigation.

   • herdr 0.9.5 stable, macOS (Darwin 25.6.0, arm64), iTerm2, TERM=xterm-256color inside panes
   • printf 'سلام دنیا TESTING 123' in a pane: reversed order and unjoined letterforms — Persian needs contextual shaping, so it is doubly unreadable
   • the same command in a plain iTerm2 tab outside herdr renders correctly
   • captured the client's output through a pty: ASCII in the same line is written as contiguous runs, but every RTL letter is emitted as an individually cursor-positioned cell (ESC[2;70Hل, ESC[2;71Hا, ESC[2;72Hم, …), so the host terminal never receives a contiguous run to reorder or shape
   • a debug build that writes RTL words as contiguous logical-order runs renders correctly in iTerm2; same bytes reproduced on Linux

   Happy to provide full captures if useful. Technical follow-up posted on #5500.