vt: add ghostty_build_info API for querying build configuration

Add a new C API function ghostty_build_info() that exposes compile-time
build options to library consumers. This allows callers to query whether
SIMD, Kitty graphics protocol, and tmux control mode support were
enabled at build time.

example/c-vt-build-info/README.md

@@ -0,0 +1,17 @@
+# Example: `ghostty-vt` Build Info
+
+This contains a simple example of how to use the `ghostty-vt` build info
+API to query compile-time build configuration.
+
+This uses a `build.zig` and `Zig` to build the C program so that we
+can reuse a lot of our build logic and depend directly on our source
+tree, but Ghostty emits a standard C library that can be used with any
+C tooling.
+
+## Usage
+
+Run the program:
+
+```shell-session
+zig build run
+```

example/c-vt-build-info/build.zig

@@ -0,0 +1,42 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    const run_step = b.step("run", "Run the app");
+
+    const exe_mod = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+    });
+    exe_mod.addCSourceFiles(.{
+        .root = b.path("src"),
+        .files = &.{"main.c"},
+    });
+
+    // You'll want to use a lazy dependency here so that ghostty is only
+    // downloaded if you actually need it.
+    if (b.lazyDependency("ghostty", .{
+        // Setting simd to false will force a pure static build that
+        // doesn't even require libc, but it has a significant performance
+        // penalty. If your embedding app requires libc anyway, you should
+        // always keep simd enabled.
+        // .simd = false,
+    })) |dep| {
+        exe_mod.linkLibrary(dep.artifact("ghostty-vt"));
+    }
+
+    // Exe
+    const exe = b.addExecutable(.{
+        .name = "c_vt_build_info",
+        .root_module = exe_mod,
+    });
+    b.installArtifact(exe);
+
+    // Run
+    const run_cmd = b.addRunArtifact(exe);
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| run_cmd.addArgs(args);
+    run_step.dependOn(&run_cmd.step);
+}

example/c-vt-build-info/build.zig.zon

@@ -0,0 +1,24 @@
+.{
+    .name = .c_vt_build_info,
+    .version = "0.0.0",
+    .fingerprint = 0xc6b57ed4f83fb16,
+    .minimum_zig_version = "0.15.1",
+    .dependencies = .{
+        // Ghostty dependency. In reality, you'd probably use a URL-based
+        // dependency like the one showed (and commented out) below this one.
+        // We use a path dependency here for simplicity and to ensure our
+        // examples always test against the source they're bundled with.
+        .ghostty = .{ .path = "../../" },
+
+        // Example of what a URL-based dependency looks like:
+        // .ghostty = .{
+        //     .url = "https://github.com/ghostty-org/ghostty/archive/COMMIT.tar.gz",
+        //     .hash = "N-V-__8AAMVLTABmYkLqhZPLXnMl-KyN38R8UVYqGrxqO36s",
+        // },
+    },
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+    },
+}

example/c-vt-build-info/src/main.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <ghostty/vt.h>
+
+//! [build-info-query]
+void query_build_info() {
+  bool simd = false;
+  bool kitty_graphics = false;
+  bool tmux_control_mode = false;
+
+  ghostty_build_info(GHOSTTY_BUILD_INFO_SIMD, &simd);
+  ghostty_build_info(GHOSTTY_BUILD_INFO_KITTY_GRAPHICS, &kitty_graphics);
+  ghostty_build_info(GHOSTTY_BUILD_INFO_TMUX_CONTROL_MODE, &tmux_control_mode);
+
+  printf("SIMD: %s\n", simd ? "enabled" : "disabled");
+  printf("Kitty graphics: %s\n", kitty_graphics ? "enabled" : "disabled");
+  printf("Tmux control mode: %s\n", tmux_control_mode ? "enabled" : "disabled");
+}
+//! [build-info-query]
+
+int main() {
+  query_build_info();
+  return 0;
+}

include/ghostty/vt.h

@@ -34,6 +34,7 @@
  * - @ref osc "OSC Parser" - Parse OSC (Operating System Command) sequences
  * - @ref sgr "SGR Parser" - Parse SGR (Select Graphic Rendition) sequences
  * - @ref paste "Paste Utilities" - Validate paste data safety
+ * - @ref build_info "Build Info" - Query compile-time build configuration
  * - @ref allocator "Memory Management" - Memory management and custom allocators
  * - @ref wasm "WebAssembly Utilities" - WebAssembly convenience functions
  *
@@ -45,6 +46,7 @@
  * @section examples_sec Examples
  *
  * Complete working examples:
+ * - @ref c-vt-build-info/src/main.c - Build info query example
  * - @ref c-vt/src/main.c - OSC parser example
  * - @ref c-vt-encode-key/src/main.c - Key encoding example
  * - @ref c-vt-encode-mouse/src/main.c - Mouse encoding example
@@ -55,6 +57,11 @@
  *
  */
 
+/** @example c-vt-build-info/src/main.c
+ * This example demonstrates how to query compile-time build configuration
+ * such as SIMD support, Kitty graphics, and tmux control mode availability.
+ */
+
 /** @example c-vt/src/main.c
  * This example demonstrates how to use the OSC parser to parse an OSC sequence,
  * extract command information, and retrieve command-specific data like window titles.
@@ -100,6 +107,7 @@ extern "C" {
 
 #include <ghostty/vt/types.h>
 #include <ghostty/vt/allocator.h>
+#include <ghostty/vt/build_info.h>
 #include <ghostty/vt/color.h>
 #include <ghostty/vt/focus.h>
 #include <ghostty/vt/formatter.h>

include/ghostty/vt/build_info.h

@@ -0,0 +1,86 @@
+/**
+ * @file build_info.h
+ *
+ * Build info - query compile-time build configuration of libghostty-vt.
+ */
+
+#ifndef GHOSTTY_VT_BUILD_INFO_H
+#define GHOSTTY_VT_BUILD_INFO_H
+
+/** @defgroup build_info Build Info
+ *
+ * Query compile-time build configuration of libghostty-vt.
+ *
+ * These values reflect the options the library was built with and are
+ * constant for the lifetime of the process.
+ *
+ * ## Basic Usage
+ *
+ * Use ghostty_build_info() to query individual build options:
+ *
+ * @snippet c-vt-build-info/src/main.c build-info-query
+ *
+ * @{
+ */
+
+#include <stdbool.h>
+
+#include <ghostty/vt/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Build info data types that can be queried.
+ *
+ * Each variant documents the expected output pointer type.
+ */
+typedef enum {
+  /** Invalid data type. Never results in any data extraction. */
+  GHOSTTY_BUILD_INFO_INVALID = 0,
+
+  /**
+   * Whether SIMD-accelerated code paths are enabled.
+   *
+   * Output type: bool *
+   */
+  GHOSTTY_BUILD_INFO_SIMD = 1,
+
+  /**
+   * Whether Kitty graphics protocol support is available.
+   *
+   * Output type: bool *
+   */
+  GHOSTTY_BUILD_INFO_KITTY_GRAPHICS = 2,
+
+  /**
+   * Whether tmux control mode support is available.
+   *
+   * Output type: bool *
+   */
+  GHOSTTY_BUILD_INFO_TMUX_CONTROL_MODE = 3,
+} GhosttyBuildInfo;
+
+/**
+ * Query a compile-time build configuration value.
+ *
+ * The caller must pass a pointer to the correct output type for the
+ * requested data (see GhosttyBuildInfo variants for types).
+ *
+ * @param data The build info field to query
+ * @param out Pointer to store the result (type depends on data parameter)
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_INVALID_VALUE if the
+ *         data type is invalid
+ *
+ * @ingroup build_info
+ */
+GhosttyResult ghostty_build_info(GhosttyBuildInfo data, void *out);
+
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */
+
+#endif /* GHOSTTY_VT_BUILD_INFO_H */

src/lib_vt.zig

@@ -217,6 +217,7 @@ comptime {
         @export(&c.grid_ref_row, .{ .name = "ghostty_grid_ref_row" });
         @export(&c.grid_ref_graphemes, .{ .name = "ghostty_grid_ref_graphemes" });
         @export(&c.grid_ref_style, .{ .name = "ghostty_grid_ref_style" });
+        @export(&c.build_info, .{ .name = "ghostty_build_info" });
 
         // On Wasm we need to export our allocator convenience functions.
         if (builtin.target.cpu.arch.isWasm()) {

src/terminal/c/build_info.zig

@@ -0,0 +1,79 @@
+const std = @import("std");
+const build_options = @import("terminal_options");
+const Result = @import("result.zig").Result;
+
+const log = std.log.scoped(.build_info_c);
+
+/// C: GhosttyBuildInfo
+pub const BuildInfo = enum(c_int) {
+    invalid = 0,
+    simd = 1,
+    kitty_graphics = 2,
+    tmux_control_mode = 3,
+
+    /// Output type expected for querying the data of the given kind.
+    pub fn OutType(comptime self: BuildInfo) type {
+        return switch (self) {
+            .invalid => void,
+            .simd, .kitty_graphics, .tmux_control_mode => bool,
+        };
+    }
+};
+
+pub fn get(
+    data: BuildInfo,
+    out: ?*anyopaque,
+) callconv(.c) Result {
+    if (comptime std.debug.runtime_safety) {
+        _ = std.meta.intToEnum(BuildInfo, @intFromEnum(data)) catch {
+            log.warn("build_info invalid data value={d}", .{@intFromEnum(data)});
+            return .invalid_value;
+        };
+    }
+
+    return switch (data) {
+        inline else => |comptime_data| getTyped(
+            comptime_data,
+            @ptrCast(@alignCast(out)),
+        ),
+    };
+}
+
+fn getTyped(
+    comptime data: BuildInfo,
+    out: *data.OutType(),
+) Result {
+    switch (data) {
+        .invalid => return .invalid_value,
+        .simd => out.* = build_options.simd,
+        .kitty_graphics => out.* = build_options.kitty_graphics,
+        .tmux_control_mode => out.* = build_options.tmux_control_mode,
+    }
+
+    return .success;
+}
+
+test "get simd" {
+    const testing = std.testing;
+    var value: bool = undefined;
+    try testing.expectEqual(Result.success, get(.simd, @ptrCast(&value)));
+    try testing.expectEqual(build_options.simd, value);
+}
+
+test "get kitty_graphics" {
+    const testing = std.testing;
+    var value: bool = undefined;
+    try testing.expectEqual(Result.success, get(.kitty_graphics, @ptrCast(&value)));
+    try testing.expectEqual(build_options.kitty_graphics, value);
+}
+
+test "get tmux_control_mode" {
+    const testing = std.testing;
+    var value: bool = undefined;
+    try testing.expectEqual(Result.success, get(.tmux_control_mode, @ptrCast(&value)));
+    try testing.expectEqual(build_options.tmux_control_mode, value);
+}
+
+test "get invalid" {
+    try std.testing.expectEqual(Result.invalid_value, get(.invalid, null));
+}

src/terminal/c/main.zig

@@ -1,3 +1,4 @@
+const buildpkg = @import("build_info.zig");
 pub const cell = @import("cell.zig");
 pub const color = @import("color.zig");
 pub const focus = @import("focus.zig");
@@ -17,6 +18,8 @@ pub const style = @import("style.zig");
 pub const terminal = @import("terminal.zig");
 
 // The full C API, unexported.
+pub const build_info = buildpkg.get;
+
 pub const osc_new = osc.new;
 pub const osc_free = osc.free;
 pub const osc_reset = osc.reset;
@@ -136,6 +139,7 @@ pub const grid_ref_graphemes = grid_ref.grid_ref_graphemes;
 pub const grid_ref_style = grid_ref.grid_ref_style;
 
 test {
+    _ = buildpkg;
     _ = cell;
     _ = color;
     _ = grid_ref;