SKILL.md
$27
Tool
Version
CMake
3.19+
Ninja
any
C compiler
clang/gcc
Zig
0.15.x (on PATH)
macOS
Xcode CLT or Xcode
Build & Run
# Clone
git clone https://github.com/ghostty-org/ghostling.git
cd ghostling
# Debug build (slow — safety checks enabled)
cmake -B build -G Ninja
cmake --build build
./build/ghostling
# Release build (optimized)
cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build
./build/ghostlingAfter first configure, only the build step is needed:
cmake --build buildWarning: Debug builds are very slow due to Ghostty's safety/correctness assertions. Always benchmark with Release builds.
Project Structure
ghostling/
├── main.c # Entire terminal implementation (single file)
├── CMakeLists.txt # Build config; fetches libghostty-vt + Raylib
└── demo.gifCore libghostty-vt API Patterns
All implementation lives in main.c. Below are the key patterns extracted from it.
1. Initialize the Terminal
#include "ghostty.h" // provided by libghostty-vt via CMake
// Create terminal with cols x rows cells
ghostty_terminal_t *terminal = ghostty_terminal_new(
&(ghostty_terminal_config_t){
.cols = cols,
.rows = rows,
}
);
if (!terminal) { /* handle error */ }2. Write Data from PTY into the Terminal
// Read from PTY fd, feed raw bytes to libghostty-vt
ssize_t n = read(pty_fd, buf, sizeof(buf));
if (n > 0) {
ghostty_terminal_write(terminal, buf, (size_t)n);
}3. Send Keyboard Input
// libghostty-vt encodes the correct escape sequences
ghostty_key_event_t ev = {
.key = GHOSTTY_KEY_A, // key enum
.mods = GHOSTTY_MODS_CTRL, // modifier flags
.action = GHOSTTY_ACTION_PRESS,
.composing = false,
};
uint8_t out[64];
size_t out_len = 0;
ghostty_terminal_key(terminal, &ev, out, sizeof(out), &out_len);
// Write encoded bytes to PTY
if (out_len > 0) write(pty_fd, out, out_len);4. Send Mouse Events
ghostty_mouse_event_t mev = {
.x = cell_col, // cell column
.y = cell_row, // cell row
.button = GHOSTTY_MOUSE_LEFT,
.action = GHOSTTY_MOUSE_PRESS,
.mods = GHOSTTY_MODS_NONE,
};
uint8_t out[64];
size_t out_len = 0;
ghostty_terminal_mouse(terminal, &mev, out, sizeof(out), &out_len);
if (out_len > 0) write(pty_fd, out, out_len);5. Resize the Terminal
ghostty_terminal_resize(terminal, new_cols, new_rows);
// libghostty-vt handles text reflow automatically
// Send SIGWINCH to the child process after this
struct winsize ws = { .ws_col = new_cols, .ws_row = new_rows };
ioctl(pty_fd, TIOCSWINSZ, &ws);
kill(child_pid, SIGWINCH);6. Render: Walk the Render State
The render state API tells you exactly which cells changed and how to draw them — no need to redraw everything every frame.
// Get render state handle
ghostty_render_state_t *rs = ghostty_terminal_render_state(terminal);
// Begin a render pass (snapshot current state)
ghostty_render_state_begin(rs);
// Iterate dirty cells
ghostty_render_cell_iter_t iter = {0};
ghostty_render_cell_t cell;
while (ghostty_render_state_next_cell(rs, &iter, &cell)) {
// cell.col, cell.row — grid position
// cell.codepoint — Unicode codepoint (0 = empty)
// cell.fg.r/g/b — foreground RGB
// cell.bg.r/g/b — background RGB
// cell.attrs.bold — bold flag
// cell.attrs.italic — italic flag
// cell.attrs.reverse — reverse video
// Example: draw with Raylib
Color fg = { cell.fg.r, cell.fg.g, cell.fg.b, 255 };
Color bg = { cell.bg.r, cell.bg.g, cell.bg.b, 255 };
Rectangle rect = {
.x = cell.col * cell_width,
.y = cell.row * cell_height,
.width = cell_width,
.height = cell_height,
};
DrawRectangleRec(rect, bg);
if (cell.codepoint != 0) {
char glyph[8] = {0};
// encode codepoint to UTF-8 yourself or use a helper
encode_utf8(cell.codepoint, glyph);
DrawText(glyph, (int)rect.x, (int)rect.y, font_size, fg);
}
}
// End render pass (marks cells as clean)
ghostty_render_state_end(rs);7. Scrollback
// Scroll viewport up/down by N rows
ghostty_terminal_scroll(terminal, -3); // scroll up 3
ghostty_terminal_scroll(terminal, 3); // scroll down 3
// Scroll to bottom
ghostty_terminal_scroll_bottom(terminal);8. Cursor Position
ghostty_cursor_t cursor;
ghostty_terminal_cursor(terminal, &cursor);
// cursor.col, cursor.row — cell position
// cursor.visible — bool
// cursor.shape — GHOSTTY_CURSOR_BLOCK, _UNDERLINE, _BAR9. Cleanup
ghostty_terminal_free(terminal);PTY Setup (POSIX)
libghostty-vt has no PTY management — you own this:
#include <pty.h> // openpty
#include <unistd.h>
#include <stdlib.h>
int master_fd, slave_fd;
struct winsize ws = { .ws_row = rows, .ws_col = cols,
.ws_xpixel = 0, .ws_ypixel = 0 };
openpty(&master_fd, &slave_fd, NULL, NULL, &ws);
pid_t child = fork();
if (child == 0) {
// Child: become session leader, attach slave PTY
setsid();
ioctl(slave_fd, TIOCSCTTY, 0);
dup2(slave_fd, STDIN_FILENO);
dup2(slave_fd, STDOUT_FILENO);
dup2(slave_fd, STDERR_FILENO);
close(master_fd);
close(slave_fd);
char *shell = getenv("SHELL");
if (!shell) shell = "/bin/sh";
execl(shell, shell, NULL);
_exit(1);
}
// Parent: use master_fd for read/write
close(slave_fd);CMakeLists.txt Pattern
The project fetches libghostty-vt automatically via CMake FetchContent:
cmake_minimum_required(VERSION 3.19)
project(ghostling C)
include(FetchContent)
# libghostty-vt
FetchContent_Declare(
libghostty
URL https://release.files.ghostty.org/tip/libghostty-vt-<platform>.tar.gz
)
FetchContent_MakeAvailable(libghostty)
# Raylib
FetchContent_Declare(
raylib
GIT_REPOSITORY https://github.com/raysan5/raylib.git
GIT_TAG 5.0
)
FetchContent_MakeAvailable(raylib)
add_executable(ghostling main.c)
target_link_libraries(ghostling PRIVATE ghostty-vt raylib)Key Enums & Constants
// Keys
GHOSTTY_KEY_A … GHOSTTY_KEY_Z
GHOSTTY_KEY_UP, GHOSTTY_KEY_DOWN, GHOSTTY_KEY_LEFT, GHOSTTY_KEY_RIGHT
GHOSTTY_KEY_ENTER, GHOSTTY_KEY_BACKSPACE, GHOSTTY_KEY_ESCAPE, GHOSTTY_KEY_TAB
GHOSTTY_KEY_F1 … GHOSTTY_KEY_F12
// Modifiers (bitmask)
GHOSTTY_MODS_NONE
GHOSTTY_MODS_SHIFT
GHOSTTY_MODS_CTRL
GHOSTTY_MODS_ALT
GHOSTTY_MODS_SUPER
// Mouse buttons
GHOSTTY_MOUSE_LEFT, GHOSTTY_MOUSE_RIGHT, GHOSTTY_MOUSE_MIDDLE
GHOSTTY_MOUSE_WHEEL_UP, GHOSTTY_MOUSE_WHEEL_DOWN
// Cursor shapes
GHOSTTY_CURSOR_BLOCK, GHOSTTY_CURSOR_UNDERLINE, GHOSTTY_CURSOR_BARCommon Patterns
Non-blocking PTY Read Loop
// Set master_fd non-blocking
fcntl(master_fd, F_SETFL, O_NONBLOCK);
// In your main loop:
uint8_t buf[4096];
ssize_t n;
while ((n = read(master_fd, buf, sizeof(buf))) > 0) {
ghostty_terminal_write(terminal, buf, (size_t)n);
}
// EAGAIN means no data available — not an errorRaylib Key → ghostty_key_t Mapping
ghostty_key_t raylib_key_to_ghostty(int rl_key) {
switch (rl_key) {
case KEY_A: return GHOSTTY_KEY_A;
case KEY_ENTER: return GHOSTTY_KEY_ENTER;
case KEY_BACKSPACE: return GHOSTTY_KEY_BACKSPACE;
case KEY_UP: return GHOSTTY_KEY_UP;
case KEY_DOWN: return GHOSTTY_KEY_DOWN;
// ... etc
default: return GHOSTTY_KEY_INVALID;
}
}Scrollbar Rendering
int total_rows = ghostty_terminal_total_rows(terminal);
int viewport_rows = rows; // your grid height
int scroll_offset = ghostty_terminal_scroll_offset(terminal);
float bar_h = (float)viewport_rows / total_rows * window_height;
float bar_y = (float)scroll_offset / total_rows * window_height;
DrawRectangle(window_width - SCROLLBAR_W, (int)bar_y,
SCROLLBAR_W, (int)bar_h, GRAY);Troubleshooting
Problem
Fix
Build fails: zig not found
Install Zig 0.15.x and ensure it's on $PATH
Debug build extremely slow
Use Release: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
Terminal renders garbage
Verify you're calling ghostty_render_state_begin before iterating cells and ghostty_render_state_end after
Child process not getting resize
Call ioctl(pty_fd, TIOCSWINSZ, &ws) AND kill(child_pid, SIGWINCH) after ghostty_terminal_resize
Kitty keyboard protocol broken
Known upstream Raylib/GLFW limitation — libghostty-vt supports it correctly but needs richer input events
Colors look wrong
Check cell.fg/cell.bg — libghostty-vt resolves palette to RGB, use those values directly
ghostty_terminal_write crashes
Ensure buffer passed is valid and len > 0; never pass NULL
What libghostty-vt Will NOT Do For You
You must implement these yourself:
- PTY creation and process management
- Window creation and event loop
- Font loading and glyph rendering
- Clipboard read/write (OSC 52 bytes are provided, handling is yours)
- Tabs, splits, multiple windows
- Configuration UI
API Reference
Full libghostty-vt C API docs: https://libghostty.tip.ghostty.org/group__render.html