opencode TUI renders boxes in legacy Windows console: NSimSun lacks U+2580 glyph
Xukun-Liu · ghdev · 2026-10-15
- Symptom: opencode's TUI shows a row of hollow boxes under the prompt panel when launched from legacy conhost (cmd.exe) on Windows; Windows Terminal is unaffected due to its own font fallback.
- Root cause: The panel edge uses ▀ (U+2580) and ╹ (U+2579), but Chinese Windows' default console font NSimSun follows GB2312 coverage, which lacks both codepoints — missing glyphs render as hollow boxes.
- Evidence: The author drew each character into a real conhost window (8x16 cells, NSimSun) and read back pixels into a comparison table; switching to Consolas renders both correctly, confirming font coverage rather than a conhost limitation, backed by captured ANSI streams.
- Workaround: Use Windows Terminal or change the console font; the startup logo also uses U+2580 and is affected.
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