Add Parser and Terminal C API to libghostty-vt

[domenkozar]

Following the work in #8840, I'd like to extend the libghostty-vt C API with bindings for the VT parser and terminal emulator.

Parser API exposes the state machine for byte-by-byte parsing of VT escape sequences (CSI, ESC, DCS, OSC, APC), with accessors for sequence details.

Terminal API provides a higher level write/read interface for full terminal emulation: write bytes (including escape sequences), query cursor position, get screen dimensions, resize, and extract plain text content.

Both follow existing conventions in src/terminal/c/ (opaque handles, allocator parameter, Result return type) and include C headers with documentation.

Branch with implementation: https://github.com/domenkozar/ghostty/tree/libvt-c-api

Code was written using Claude Opus 4.6 via Claude Code.

[domenkozar]

I see that @mitchellh added #11506, I have 4 more commits for VT state stuff at https://github.com/domenkozar/ghostty/commits/vt-state-query-c-api/

[domenkozar]

Updated branch rebased on main and is_mode_set removed (already covered by mode_get in main). Here's what each commit adds:

Terminal state queries:

• 633eaa58b ghostty_terminal_get_size, ghostty_terminal_get_cursor_pos, ghostty_terminal_get_cursor_visible
• 8eefff9ef ghostty_terminal_is_alt_screen, ghostty_terminal_kitty_keyboard_flags
• 33ab52096 ghostty_terminal_total_rows, ghostty_terminal_scrollback_rows

Row/cell/style access:

• be83577bf ghostty_terminal_get_row, ghostty_terminal_get_cells, ghostty_terminal_get_style, ghostty_terminal_get_grapheme

VT stream parser:

• 63e885d84 ghostty_parser_new/free/reset/next/csi/esc/dcs

Content serialization:

• d10caf740 ghostty_terminal_plain_string, ghostty_terminal_dump (+ free variants)

Host terminal control:

• 9608761b1 ghostty_host_enable_raw_mode, ghostty_host_disable_raw_mode, ghostty_host_get_size

Write extensions:

• 3e53c08c5 ghostty_terminal_vt_write_ex (write with row count tracking)
• e171b0ad9 ghostty_terminal_callback_writer_new/free/write (per sequence callback)

Branch: https://github.com/domenkozar/ghostty/tree/vt-state-query-c-api

[mitchellh]

Thanks @domenkozar I just noticed this discussion. This will help me with the roadmap on some of the stuff I'm working on.

[mitchellh]

I think all terminal state and row/cell/style access should be covered now by #11676

[domenkozar]

Remaining commits not yet covered by main:

Scrollback row count queries:

• 017d86b9c ghostty_terminal_total_rows, ghostty_terminal_scrollback_rows

VT stream parser:

• 0996e2d90 ghostty_parser_new/free/reset/next/csi/esc/dcs

Content serialization:

• 9b6854ba7 ghostty_terminal_plain_string, ghostty_terminal_dump (+ free variants)

Host terminal control:

• 52020e29c ghostty_host_enable_raw_mode, ghostty_host_disable_raw_mode, ghostty_host_get_size

Write extensions:

• b1ddf17eb ghostty_terminal_vt_write_ex (write with row count tracking)
• 68f8387fc ghostty_terminal_callback_writer_new/free/write (per sequence callback)

Branch: https://github.com/domenkozar/ghostty/tree/vt-state-query-c-api

[mitchellh]

Note: ghostty_host_enable_raw_mode, ghostty_host_disable_raw_mode, ghostty_host_get_size unlikely we'll ever do this, since libghostty-vt doesn't create/manage a pty.