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SystemTrayTerminal — Remaining Compatibility Gaps (~4-5%)

Current compatibility score: ~99-100% (all gaps resolved: OSC resets, DECRQM, DECSCA, DECDWL/DECDHL, DECBI/DECFI, DECLRMM, BiDi/RTL).

This document lists all previously identified gaps — now resolved.

HIGH Priority

1. OSC 104/110/111/112 — Color Reset

The SET counterparts (OSC 4/10/11/12) are implemented, but their reset variants are missing.

  • OSC 104;index ST — Reset palette color at index to default
  • OSC 104 ST (no index) — Reset entire palette to defaults
  • OSC 110 ST — Reset foreground color to default
  • OSC 111 ST — Reset background color to default
  • OSC 112 ST — Reset cursor color to default

Where: handleOSC() in SystemTrayTerminal.swift Effort: Low — just clear paletteOverrides[idx], dynamicFG, dynamicBG, dynamicCursor

2. DECSTR — Soft Reset (CSI ! p)

Full reset (ESC c / RIS) is implemented, but soft reset (DECSTR) is missing. Many TUI apps use DECSTR instead of RIS.

What DECSTR resets:

  • Text attributes (SGR) to defaults
  • Insert mode off
  • Origin mode off
  • Auto-wrap on
  • Cursor visible
  • Scroll region to full screen
  • Character sets to default
  • Saved cursor state

What DECSTR does NOT reset:

  • Screen contents
  • Tab stops
  • Window size
  • Palette/colors

Where: doCSIBang() handler for CSI ! p Effort: Low — subset of fullReset() without clearing grid/scrollback

3. ICH — Insert Characters (CSI Ps @)

Insert N blank characters at cursor, shifting existing content right. Different from IRM (insert mode) which affects put() — ICH is an explicit CSI command.

Where: doCSI() — add case 0x40 Effort: Low

4. DCH — Delete Characters (CSI Ps P)

Delete N characters at cursor, shifting remaining content left and filling from the right with blanks.

Where: doCSI() — check if case 0x50 exists, implement if missing Effort: Low

MEDIUM Priority

5. DECRQM for Standard Modes (CSI Ps $ p)

Private mode DECRQM (CSI ? Ps $ p) is implemented, but standard mode DECRQM (CSI Ps $ p) is missing. Some apps query standard modes like IRM (4), LNM (20).

Response format: CSI Ps; Pm $ y where Pm = 1 (set), 2 (reset), 0 (unknown) Where: doCSIDollar() handler Effort: Low

6. CSI t — Window Manipulation (xterm)

Window manipulation sequences used by some TUI apps:

  • CSI 8;rows;cols t — Resize window (already have onResize callback)
  • CSI 14 t — Report window size in pixels → respond CSI 4;height;width t
  • CSI 18 t — Report text area size in chars → respond CSI 8;rows;cols t
  • CSI 22;0 t / CSI 22;2 t — Push title to stack
  • CSI 23;0 t / CSI 23;2 t — Pop title from stack

Where: doCSI() — add case 0x74 Effort: Medium — need title stack and pixel dimension reporting

7. REP — Repeat Character (CSI Ps b)

Repeat the last printed character N times. Some apps use this for efficient screen filling.

Where: doCSI() — add case 0x62, use lastChar Effort: Low — already tracking lastChar

8. SU / SD — Scroll Up/Down (CSI Ps S / CSI Ps T)

Scroll the scroll region up/down by N lines without moving the cursor. Different from scrolling via cursor movement.

Where: doCSI() — check if cases 0x53 / 0x54 exist Effort: Low

9. VPA — Vertical Position Absolute (CSI Ps d)

Move cursor to absolute row. Should respect origin mode.

Where: doCSI() — check if case 0x64 exists and handles origin mode correctly Effort: Low

LOW Priority

10. Protected Attributes (DECSCA / SPA / EPA)

Character protection prevents erasure of marked cells by ED/EL/ECH.

  • SGR 1 (DECSCA): CSI 1 " q — set protection attribute
  • SGR 0 (DECSCA): CSI 0 " q — reset protection attribute
  • SPA/EPA: ESC V / ESC W — start/end guarded area

Effort: Medium — requires checking protection flag in all erase operations Usage: Rare in modern apps

11. DECDWL / DECDHL — Double Width/Height Lines

  • ESC # 6 — Double-width line (DECDWL)
  • ESC # 3 — Double-height line, top half (DECDHL)
  • ESC # 4 — Double-height line, bottom half (DECDHL)

Effort: High — requires per-line width attribute and renderer changes Usage: Very rare, mostly legacy VT100 demos

12. DECBI / DECFI — Back/Forward Index

  • ESC 6 — Back Index (DECBI): move cursor left, scroll right if at left margin
  • ESC 9 — Forward Index (DECFI): move cursor right, scroll left if at right margin

Effort: Medium Usage: Rare

13. BiDi / Right-to-Left Text

Unicode bidirectional text rendering for Arabic, Hebrew etc.

Effort: Very High — requires UAX #9 bidi algorithm Usage: Important for i18n but extremely complex

14. DECLRMM — Left/Right Margin Mode

  • CSI ? 69 h — Enable left/right margins
  • CSI Pl ; Pr s — Set left/right margins (DECSLRM, conflicts with SCOSC)

Allows horizontal scroll regions. Very few apps use this.

Effort: High — affects all cursor movement and scroll operations Usage: Rare

Checklist

  • OSC 104/110/111/112 (color reset)
  • DECSTR (soft reset, CSI ! p)
  • ICH (insert characters, CSI @)
  • DCH (delete characters, CSI P)
  • DECRQM standard modes (CSI $ p)
  • CSI t (window manipulation + title push/pop)
  • REP (repeat character, CSI b)
  • SU/SD (scroll up/down, CSI S/T)
  • VPA origin mode check
  • DECSCA / SPA / EPA (protected attributes)
  • DECDWL / DECDHL (double width/height)
  • DECBI / DECFI (back/forward index)
  • BiDi / RTL text (Core Text based bidi reordering)
  • DECLRMM (left/right margins)