Ghostling feature-parity gate¶

Ghostling is Revenant's minimum modern-terminal capability floor. The goal is not merely to use the same parser: each advertised feature must cross the backend boundary and work through the real X11 interface.

The original MVP goal required every item in this checklist to be Present, plus the daily xterm-driver advantages that make Revenant more than a Ghostling port. Revenant has since shipped with Kitty graphics as an explicit exception. Keep that row honestly Missing while its TODO series is parked.

“Partial” means libghostty already supplies state or encoding, but Revenant has not finished the user-visible integration or acceptance coverage.

Advertised Ghostling capability	Status	Promotion still required
Resize with text reflow	Present	Retain live Readline, large-history, and stale-frame regression coverage.
Full 24-bit color and 256-color palette	Present	Retain xterm color0 through color15 resource and OSC palette coverage.
Bold, italic, and inverse styles	Present	Retain real bold/italic/bold-italic Xft roles and style-combination coverage; bitmap synthetic bold remains an xterm-fidelity task.
Unicode and multi-codepoint graphemes	Present	Retain Unicode 17 emoji roles, general fontconfig fallback, contextual adjacent-cell shaping, color formats, and atomic role selection.
Keyboard input with Shift, Ctrl, Alt, and Super	Present	Retain exact normal/application mode, modifier, editing/function-key, non-US, XIM, and no-XIM UTF-8 fixtures.
Kitty keyboard protocol	Present	Retain exact state-stack and X11 press/repeat/release fixtures, including the synthetic F13 map and composed/non-US UTF-8 coverage.
Kitty graphics protocol	Missing	Expose image placement/lifecycle through terminal.h and safely composite it in X11. Parser state alone is not promotion.
X10, normal, button-event, and any-event mouse tracking	Present	Retain backend and Xvfb routing coverage.
SGR, URxvt, UTF-8, and X10 mouse reports	Present	Retain exact encoding coverage; Revenant also supports SGR-pixel reports.
Scroll wheel for history or application forwarding	Present	Retain local/application routing and Shift-override coverage.
Draggable scrollbar	Present	Retain Xaw thumb, placement, and deep-history coverage.
Focus reporting (CSI I and CSI O)	Present	Retain real focus-event coverage gated by DEC private mode 1004.

Current total: 11 Present, 0 Partial, 1 Missing.

Kitty keyboard acceptance backlog¶

The terminal core parses Kitty keyboard configuration and its encoder consults current terminal state. Revenant now also preserves X11 press, detectable autorepeat, and release actions at that boundary. Promotion is backed by the following maintained checks:

• [x] Query current flags with CSI ? u, including correct ordering with a following device-attributes query.
• [x] Set, augment, and clear flags with all three CSI = flags ; mode u modes.
• [x] Push and pop nested flag sets, restoring the outer application's state.
• [x] Preserve the legacy encoding when no flags are active.
• [x] Preserve libghostty's default fixterms exception to legacy encoding: Ctrl-I is CSI 105;5 u while Tab is 0x09, even before Kitty flags are enabled. This intentional xterm incompatibility is recorded in the xterm differences ledger.
• [x] Flag 1: disambiguate Escape, Ctrl/Alt combinations, Tab, Enter, and Backspace.
• [x] Flag 2: distinguish press, autorepeat, and release. The X11 adapter uses XKB detectable autorepeat when available and the conventional paired release/press fallback on older servers.
• [x] Flag 4: report shifted and base-layout alternatives.
• [x] Flag 8: encode ordinary printable keys as escape sequences and verify its interaction with DECCKM and keypad modes.
• [x] Flag 16: report associated text, including composed/XIM UTF-8 input.
• [x] Preserve Shift, Ctrl, Alt, Super, Caps Lock, and Num Lock modifiers in the combinations representable by X11.
• [x] Keep bracketed paste, mouse reports, xterm local bindings, popup menus, and the OSC 8 Shift gesture outside the keyboard protocol.
• [x] Turn real application failures reported by the maintainer into named, reproducible fixtures with exact expected PTY bytes.

tests/xvfb-keyboard.sh protects the zero-flags Ctrl-I/Tab split and the no-XIM keysym-to-UTF-8 fallback. tests/xvfb-kitty-keyboard.sh drives real X key events and compares exact PTY bytes for press, repeat, release, shifted alternatives, associated text, and a bare modifier, including an F13 key installed into Xvfb's otherwise limited map. tests/xvfb-keyboard-matrix.sh adds normal/application cursor and keypad modes, Shift/Ctrl/Alt/Super modifiers, editing/function keys, a remapped non-US character, and built-in XIM Compose. The backend self-test protects query ordering, every set mode, and nested stack restoration. More layouts remain useful matrix expansion, but are no longer missing protocol plumbing.

The wire format and manual probes are documented in the TDN Kitty keyboard reference. Run just probe csi-u-kitty-keyboard input-keyboard-kitty from a checkout for the maintained interactive acceptance probe; it preserves exact bytes, decodes event types, and verifies flag-stack restoration.

Definition of “better than Ghostling”¶

Passing this checklist establishes the modern capability floor. Revenant exceeds it by preserving the xterm daily-driver contract and by shipping tested local features such as named X11 selections, reflow-safe historical selection, middle-button paste, OSC 8 interaction, popup menus, font switching, cursor policy, and X resource configuration. Neither half substitutes for the other.