Some parts of libghostty-vt are optional. A program that only draws a terminal doesn't need search or snapshots, for example, so the library can be built without them to make it smaller. You choose features when you build the library, with the -Dvt-features build option.

Optional features don't require program changes. Every function in our C headers exist in every build, so a program links and loads the same way against any set of enabled features. When you call a function whose feature was disabled, the function does nothing and returns GHOSTTY_UNSUPPORTED.

Feature	Functions
color	ghostty_color_*
formatter	ghostty_formatter_*
glyph_protocol	None. It lets applications register custom glyphs with Ghostty's glyph protocol.
grid_introspection	ghostty_grid_ref_, ghostty_tracked_grid_ref_, ghostty_cell_get, ghostty_row_get, ghostty_terminal_grid_ref_track()
input_encode	ghostty_key_event_, ghostty_key_encoder_, ghostty_mouse_event_, ghostty_mouse_encoder_, ghostty_focus_encode(), ghostty_paste_*, ghostty_terminal_paste()
kitty_graphics	ghostty_kitty_graphics_*, and the Kitty options and data of ghostty_terminal_set() and ghostty_terminal_get()
render_state	ghostty_render_state_*
search	ghostty_search_*
selection	ghostty_terminal_select_, ghostty_terminal_selection_, ghostty_selection_gesture_*
snapshot	ghostty_snapshot_*

A few functions depend on two features:

ghostty_terminal_grid_ref() and ghostty_terminal_point_from_grid_ref() need either grid_introspection or selection.
ghostty_tracked_grid_ref_snapshot() needs both grid_introspection and snapshot.

Kitty graphics need a clock, so builds for targets without an operating system, such as wasm32-freestanding, never include kitty_graphics.

Checking for a Feature

To find out up front, for example to hide a menu item, ask ghostty_build_info() with the feature's key. Each feature has a GHOSTTY_BUILD_INFO_FEATURE_* key, except Kitty graphics, which uses GHOSTTY_BUILD_INFO_KITTY_GRAPHICS:

bool has_search = false;
ghostty_build_info(GHOSTTY_BUILD_INFO_FEATURE_SEARCH, &has_search);
if (!has_search) {
  // Hide the find bar.
}

You can also just call the function and check its result. A function that creates a handle sets the handle to NULL, so cleanup code that frees it still works:

GhosttySearch search = NULL;
GhosttyResult result = ghostty_search_new(NULL, &search, terminal);
if (result == GHOSTTY_UNSUPPORTED) {
  // This library was built without search. search is NULL.
}

Functions Without a Result

A function that doesn't return a GhosttyResult can't report GHOSTTY_UNSUPPORTED. When its feature is left out, it returns a fixed value instead:

Functions that free a handle do nothing.
Functions that return bool, such as iterator _next functions, return false.
Functions that return a number, an enum or a struct return zero or a zeroed struct. ghostty_key_event_get_utf8() returns an empty string.
ghostty_color_rgb_get(), ghostty_color_palette_default() and ghostty_color_palette_generate() fill their outputs with zeros.
ghostty_color_x11_name_count() returns 0, so the array returned by ghostty_color_x11_names() is empty.
ghostty_kitty_graphics_image() returns NULL.

In practice these values rarely matter. Most of these functions take a handle that could only come from a _new function of the same feature, and that function returned GHOSTTY_UNSUPPORTED.