libghostty: C API for SelectionGesture (#12833)

C API side of https://github.com/ghostty-org/ghostty/pull/12830

example/c-vt-selection-gesture/README.md

@@ -0,0 +1,18 @@
+# Example: `ghostty-vt` Selection Gestures
+
+This contains a simple example of how to use the `ghostty-vt` selection
+gesture API from C. It creates synthetic press, drag, release, and deep-press
+events and formats the resulting selection snapshots.
+
+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-selection-gesture/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_selection_gesture",
+        .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-selection-gesture/build.zig.zon

@@ -0,0 +1,24 @@
+.{
+    .name = .c_vt_selection_gesture,
+    .version = "0.0.0",
+    .fingerprint = 0x5a4e72d27b582404,
+    .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-selection-gesture/src/main.c

@@ -0,0 +1,162 @@
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <ghostty/vt.h>
+
+//! [selection-gesture-main]
+static void vt_write(GhosttyTerminal terminal, const char *s) {
+  ghostty_terminal_vt_write(terminal, (const uint8_t *)s, strlen(s));
+}
+
+static GhosttyGridRef ref_at(GhosttyTerminal terminal, uint16_t x, uint16_t y) {
+  GhosttyGridRef ref = GHOSTTY_INIT_SIZED(GhosttyGridRef);
+  GhosttyPoint point = {
+    .tag = GHOSTTY_POINT_TAG_ACTIVE,
+    .value = { .coordinate = { .x = x, .y = y } },
+  };
+
+  GhosttyResult result = ghostty_terminal_grid_ref(terminal, point, &ref);
+  assert(result == GHOSTTY_SUCCESS);
+  return ref;
+}
+
+static void print_selection(
+    GhosttyTerminal terminal,
+    const char *label,
+    const GhosttySelection *selection) {
+  GhosttyTerminalSelectionFormatOptions opts =
+      GHOSTTY_INIT_SIZED(GhosttyTerminalSelectionFormatOptions);
+  opts.emit = GHOSTTY_FORMATTER_FORMAT_PLAIN;
+  opts.trim = true;
+  opts.selection = selection;
+
+  uint8_t *buf = NULL;
+  size_t len = 0;
+  GhosttyResult result = ghostty_terminal_selection_format_alloc(
+      terminal, NULL, opts, &buf, &len);
+  assert(result == GHOSTTY_SUCCESS);
+
+  printf("%s: ", label);
+  fwrite(buf, 1, len, stdout);
+  printf("\n");
+
+  ghostty_free(NULL, buf, len);
+}
+
+static GhosttySelectionGestureEvent new_event(
+    GhosttySelectionGestureEventType type) {
+  GhosttySelectionGestureEvent event = NULL;
+  GhosttyResult result = ghostty_selection_gesture_event_new(NULL, &event, type);
+  assert(result == GHOSTTY_SUCCESS);
+  return event;
+}
+
+int main() {
+  GhosttyTerminal terminal;
+  GhosttyTerminalOptions opts = {
+    .cols = 20,
+    .rows = 4,
+    .max_scrollback = 100,
+  };
+  GhosttyResult result = ghostty_terminal_new(NULL, &terminal, opts);
+  assert(result == GHOSTTY_SUCCESS);
+
+  vt_write(terminal, "hello world\r\nsecond line");
+
+  GhosttySelectionGesture gesture = NULL;
+  result = ghostty_selection_gesture_new(NULL, &gesture);
+  assert(result == GHOSTTY_SUCCESS);
+
+  GhosttySelectionGestureEvent press =
+      new_event(GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_PRESS);
+  GhosttySelectionGestureEvent drag =
+      new_event(GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DRAG);
+  GhosttySelectionGestureEvent release =
+      new_event(GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_RELEASE);
+  GhosttySelectionGestureEvent deep_press =
+      new_event(GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DEEP_PRESS);
+
+  GhosttySelectionGestureGeometry geometry = {
+    .columns = 20,
+    .cell_width = 10,
+    .padding_left = 0,
+    .screen_height = 40,
+  };
+
+  // Press in the first cell. A normal single press records the click anchor but
+  // doesn't produce a selection yet, so we discard the optional output.
+  GhosttyGridRef press_ref = ref_at(terminal, 0, 0);
+  result = ghostty_selection_gesture_event_set(
+      press, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF, &press_ref);
+  assert(result == GHOSTTY_SUCCESS);
+
+  GhosttySurfacePosition press_pos = { .x = 2, .y = 8 };
+  result = ghostty_selection_gesture_event_set(
+      press, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_POSITION, &press_pos);
+  assert(result == GHOSTTY_SUCCESS);
+
+  result = ghostty_selection_gesture_event(
+      gesture, terminal, press, NULL);
+  assert(result == GHOSTTY_NO_VALUE);
+
+  // Drag across "hello". The drag event returns a selection snapshot that the
+  // embedder can apply to its UI, copy, or format immediately.
+  GhosttyGridRef drag_ref = ref_at(terminal, 4, 0);
+  result = ghostty_selection_gesture_event_set(
+      drag, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF, &drag_ref);
+  assert(result == GHOSTTY_SUCCESS);
+
+  GhosttySurfacePosition drag_pos = { .x = 46, .y = 8 };
+  result = ghostty_selection_gesture_event_set(
+      drag, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_POSITION, &drag_pos);
+  assert(result == GHOSTTY_SUCCESS);
+
+  result = ghostty_selection_gesture_event_set(
+      drag, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_GEOMETRY, &geometry);
+  assert(result == GHOSTTY_SUCCESS);
+
+  GhosttySelection selection = GHOSTTY_INIT_SIZED(GhosttySelection);
+  result = ghostty_selection_gesture_event(
+      gesture, terminal, drag, &selection);
+  assert(result == GHOSTTY_SUCCESS);
+  print_selection(terminal, "drag", &selection);
+
+  // Release updates gesture state but never produces a selection.
+  result = ghostty_selection_gesture_event_set(
+      release, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF, &drag_ref);
+  assert(result == GHOSTTY_SUCCESS);
+  result = ghostty_selection_gesture_event(
+      gesture, terminal, release, NULL);
+  assert(result == GHOSTTY_NO_VALUE);
+
+  bool dragged = false;
+  result = ghostty_selection_gesture_get(
+      gesture, terminal, GHOSTTY_SELECTION_GESTURE_DATA_DRAGGED, &dragged);
+  assert(result == GHOSTTY_SUCCESS);
+  printf("dragged: %s\n", dragged ? "true" : "false");
+
+  // Deep press uses the active click anchor to select the surrounding word.
+  ghostty_selection_gesture_reset(gesture, terminal);
+  GhosttyGridRef world_ref = ref_at(terminal, 6, 0);
+  result = ghostty_selection_gesture_event_set(
+      press, GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF, &world_ref);
+  assert(result == GHOSTTY_SUCCESS);
+  result = ghostty_selection_gesture_event(
+      gesture, terminal, press, NULL);
+  assert(result == GHOSTTY_NO_VALUE);
+
+  result = ghostty_selection_gesture_event(
+      gesture, terminal, deep_press, &selection);
+  assert(result == GHOSTTY_SUCCESS);
+  print_selection(terminal, "deep press", &selection);
+
+  ghostty_selection_gesture_event_free(deep_press);
+  ghostty_selection_gesture_event_free(release);
+  ghostty_selection_gesture_event_free(drag);
+  ghostty_selection_gesture_event_free(press);
+  ghostty_selection_gesture_free(gesture, terminal);
+  ghostty_terminal_free(terminal);
+  return 0;
+}
+//! [selection-gesture-main]

include/ghostty/vt.h

@@ -104,6 +104,11 @@
  * detect when it loses its value, and move it to a new point.
  */
 
+/** @example c-vt-selection-gesture/src/main.c
+ * This example demonstrates how to use synthetic selection gesture events to
+ * derive drag and deep-press selection snapshots.
+ */
+
 /** @example c-vt-kitty-graphics/src/main.c
  * This example demonstrates how to use the system interface to install a
  * PNG decoder callback and send a Kitty Graphics Protocol image.

include/ghostty/vt/selection.h

@@ -32,13 +32,44 @@ extern "C" {
  * for the endpoints and reconstruct a GhosttySelection from fresh snapshots
  * when needed.
  *
+ * Selection gestures provide a reusable state machine for turning UI pointer
+ * interactions into selection snapshots. A caller creates one
+ * GhosttySelectionGesture per active gesture stream, reuses typed
+ * GhosttySelectionGestureEvent objects for synthetic press, drag, release,
+ * autoscroll tick, and deep-press events, and applies each event with
+ * ghostty_selection_gesture_event(). The returned GhosttySelection is a
+ * snapshot; the embedder decides whether to render it, format/copy it, or
+ * install it as the terminal's active selection.
+ *
  * ## Examples
  *
  * @snippet c-vt-selection/src/main.c selection-main
+ * @snippet c-vt-selection-gesture/src/main.c selection-gesture-main
  *
  * @{
  */
 
+/**
+ * Opaque handle to state for interpreting terminal selection gestures.
+ *
+ * The gesture owns only the state required to interpret pointer events. Calls
+ * that use a gesture are not concurrency-safe and must be serialized with
+ * terminal mutations.
+ *
+ * @ingroup selection
+ */
+typedef struct GhosttySelectionGestureImpl* GhosttySelectionGesture;
+
+/**
+ * Opaque handle to reusable input data for selection gesture operations.
+ *
+ * Event options are set with ghostty_selection_gesture_event_set(). Individual
+ * gesture operations document which options are required or optional.
+ *
+ * @ingroup selection
+ */
+typedef struct GhosttySelectionGestureEventImpl* GhosttySelectionGestureEvent;
+
 /**
  * A snapshot selection range defined by two grid references.
  *
@@ -283,6 +314,417 @@ typedef enum GHOSTTY_ENUM_TYPED {
   GHOSTTY_SELECTION_ADJUST_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttySelectionAdjust;
 
+/**
+ * Selection behavior chosen for a gesture's click sequence.
+ *
+ * @ingroup selection
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /** Cell-granular drag selection. */
+  GHOSTTY_SELECTION_GESTURE_BEHAVIOR_CELL = 0,
+
+  /** Word selection on press and word-granular drag selection. */
+  GHOSTTY_SELECTION_GESTURE_BEHAVIOR_WORD = 1,
+
+  /** Line selection on press and line-granular drag selection. */
+  GHOSTTY_SELECTION_GESTURE_BEHAVIOR_LINE = 2,
+
+  /** Semantic command output selection on press and drag. */
+  GHOSTTY_SELECTION_GESTURE_BEHAVIOR_OUTPUT = 3,
+
+  GHOSTTY_SELECTION_GESTURE_BEHAVIOR_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttySelectionGestureBehavior;
+
+/**
+ * Selection behaviors for single-, double-, and triple-click gestures.
+ *
+ * @ingroup selection
+ */
+typedef struct {
+  /** Behavior for single-click selection gestures. */
+  GhosttySelectionGestureBehavior single_click;
+
+  /** Behavior for double-click selection gestures. */
+  GhosttySelectionGestureBehavior double_click;
+
+  /** Behavior for triple-click selection gestures. */
+  GhosttySelectionGestureBehavior triple_click;
+} GhosttySelectionGestureBehaviors;
+
+/**
+ * Display geometry used to interpret selection gesture drag events.
+ *
+ * @ingroup selection
+ */
+typedef struct {
+  /** Number of columns in the rendered terminal grid. Must be non-zero. */
+  uint32_t columns;
+
+  /** Width of one terminal cell in surface pixels. Must be non-zero. */
+  uint32_t cell_width;
+
+  /** Left padding before the terminal grid begins in surface pixels. */
+  uint32_t padding_left;
+
+  /** Height of the rendered terminal surface in surface pixels. Must be non-zero. */
+  uint32_t screen_height;
+} GhosttySelectionGestureGeometry;
+
+/**
+ * Current autoscroll direction for an active selection drag gesture.
+ *
+ * @ingroup selection
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /** No selection autoscroll is requested. */
+  GHOSTTY_SELECTION_GESTURE_AUTOSCROLL_NONE = 0,
+
+  /** Selection dragging should autoscroll the viewport upward. */
+  GHOSTTY_SELECTION_GESTURE_AUTOSCROLL_UP = 1,
+
+  /** Selection dragging should autoscroll the viewport downward. */
+  GHOSTTY_SELECTION_GESTURE_AUTOSCROLL_DOWN = 2,
+
+  GHOSTTY_SELECTION_GESTURE_AUTOSCROLL_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttySelectionGestureAutoscroll;
+
+/**
+ * Data fields readable from a selection gesture with
+ * ghostty_selection_gesture_get().
+ *
+ * @ingroup selection
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /** Current click count: uint8_t*. 0 means inactive. */
+  GHOSTTY_SELECTION_GESTURE_DATA_CLICK_COUNT = 0,
+
+  /** Whether the current/last left-click gesture has dragged: bool*. */
+  GHOSTTY_SELECTION_GESTURE_DATA_DRAGGED = 1,
+
+  /** Current autoscroll request: GhosttySelectionGestureAutoscroll*. */
+  GHOSTTY_SELECTION_GESTURE_DATA_AUTOSCROLL = 2,
+
+  /** Current gesture behavior: GhosttySelectionGestureBehavior*. */
+  GHOSTTY_SELECTION_GESTURE_DATA_BEHAVIOR = 3,
+
+  /**
+   * Current left-click anchor: GhosttyGridRef*.
+   *
+   * Returns GHOSTTY_NO_VALUE if there is no valid active anchor. On success,
+   * writes an untracked GhosttyGridRef snapshot with normal GhosttyGridRef
+   * lifetime rules.
+   */
+  GHOSTTY_SELECTION_GESTURE_DATA_ANCHOR = 4,
+
+  GHOSTTY_SELECTION_GESTURE_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttySelectionGestureData;
+
+/**
+ * Selection gesture event type.
+ *
+ * The event type is fixed when the event is created. Each event type documents
+ * which options are valid and which options are required by gesture operations.
+ *
+ * @ingroup selection
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /** Press event for ghostty_selection_gesture_event(). */
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_PRESS = 0,
+
+  /** Release event for ghostty_selection_gesture_event(). */
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_RELEASE = 1,
+
+  /** Drag event for ghostty_selection_gesture_event(). */
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DRAG = 2,
+
+  /** Autoscroll tick event for ghostty_selection_gesture_event(). */
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_AUTOSCROLL_TICK = 3,
+
+  /** Deep press event for ghostty_selection_gesture_event(). */
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DEEP_PRESS = 4,
+
+  GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttySelectionGestureEventType;
+
+/**
+ * Options stored on a reusable selection gesture event.
+ *
+ * Passing NULL as the value to ghostty_selection_gesture_event_set() clears the
+ * corresponding option.
+ *
+ * @ingroup selection
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /**
+   * Grid reference under the pointer: GhosttyGridRef*.
+   *
+   * Required for PRESS and DRAG events. Optional for RELEASE events; when unset
+   * or cleared, release records that the pointer did not map to a valid cell.
+   */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF = 0,
+
+  /**
+   * Surface-space pointer position: GhosttySurfacePosition*.
+   *
+   * Valid for PRESS, DRAG, and AUTOSCROLL_TICK.
+   */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_POSITION = 1,
+
+  /** Maximum repeat-click distance in pixels: double*. */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REPEAT_DISTANCE = 2,
+
+  /**
+   * Optional monotonic event time in nanoseconds: uint64_t*.
+   *
+   * If unset, press treats the event as untimed and only single-click behavior
+   * is available.
+   */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_TIME_NS = 3,
+
+  /** Maximum interval between repeat clicks in nanoseconds: uint64_t*. */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REPEAT_INTERVAL_NS = 4,
+
+  /**
+   * Word-boundary codepoints: GhosttyCodepoints*.
+   *
+   * The codepoints are copied into event-owned storage when set. If unset,
+   * operations that need word boundaries use Ghostty's defaults.
+   *
+   * Valid for PRESS, DRAG, AUTOSCROLL_TICK, and DEEP_PRESS.
+   */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_WORD_BOUNDARY_CODEPOINTS = 5,
+
+  /**
+   * Selection behavior table: GhosttySelectionGestureBehaviors*.
+   *
+   * If unset, press uses the default behavior table: cell, word, line.
+   */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_BEHAVIORS = 6,
+
+  /** Whether a drag or autoscroll tick should produce a rectangular selection: bool*. */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_RECTANGLE = 7,
+
+  /** Drag display geometry: GhosttySelectionGestureGeometry*. Required for DRAG and AUTOSCROLL_TICK. */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_GEOMETRY = 8,
+
+  /** Viewport coordinate for an autoscroll tick: GhosttyPointCoordinate*. Required for AUTOSCROLL_TICK. */
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_VIEWPORT = 9,
+
+  GHOSTTY_SELECTION_GESTURE_EVENT_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttySelectionGestureEventOption;
+
+/**
+ * Create a reusable selection gesture event object.
+ *
+ * @param allocator Allocator, or NULL for the default allocator
+ * @param out_event Receives the created event handle
+ * @param type Event type. This is fixed for the lifetime of the event.
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_INVALID_VALUE if out_event is
+ *         NULL or type is invalid, or GHOSTTY_OUT_OF_MEMORY if allocation fails
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_event_new(
+                                    const GhosttyAllocator* allocator,
+                                    GhosttySelectionGestureEvent* out_event,
+                                    GhosttySelectionGestureEventType type);
+
+/**
+ * Free a selection gesture event object.
+ *
+ * Passing NULL is allowed and is a no-op.
+ *
+ * @param event Selection gesture event handle to free
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API void ghostty_selection_gesture_event_free(
+                                    GhosttySelectionGestureEvent event);
+
+/**
+ * Set or clear an option on a selection gesture event.
+ *
+ * The value type depends on option and is documented by
+ * GhosttySelectionGestureEventOption. Passing NULL for value clears the option.
+ *
+ * @param event Selection gesture event handle (NULL returns GHOSTTY_INVALID_VALUE)
+ * @param option Event option to set or clear
+ * @param value Pointer to the input value for option, or NULL to clear
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_OUT_OF_MEMORY if copying
+ *         event-owned data fails, or GHOSTTY_INVALID_VALUE if event, option, or
+ *         value is invalid
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_event_set(
+                                    GhosttySelectionGestureEvent event,
+                                    GhosttySelectionGestureEventOption option,
+                                    const void* value);
+
+/**
+ * Apply a selection gesture event and return the resulting selection snapshot.
+ *
+ * This dispatches to the gesture operation matching the event's fixed type.
+ * For GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_PRESS, the event must have
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF set before calling this function.
+ * All other press options use their initialized defaults when unset or cleared.
+ *
+ * For GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_RELEASE, only
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF is valid. It is optional; if unset or
+ * cleared, release records that the pointer did not map to a valid cell. Release
+ * events update gesture state but do not produce a selection, so this function
+ * returns GHOSTTY_NO_VALUE after applying them.
+ *
+ * For GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DRAG,
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_REF and
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_GEOMETRY are required. Position,
+ * rectangle, and word-boundary codepoints are optional and use initialized
+ * defaults when unset or cleared.
+ *
+ * For GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_AUTOSCROLL_TICK,
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_VIEWPORT and
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_GEOMETRY are required. Position,
+ * rectangle, and word-boundary codepoints are optional and use initialized
+ * defaults when unset or cleared.
+ *
+ * For GHOSTTY_SELECTION_GESTURE_EVENT_TYPE_DEEP_PRESS, only
+ * GHOSTTY_SELECTION_GESTURE_EVENT_OPT_WORD_BOUNDARY_CODEPOINTS is valid. It is
+ * optional and uses initialized defaults when unset or cleared.
+ *
+ * The returned selection is not installed as the terminal's current selection.
+ * It is a snapshot with the same lifetime rules as GhosttySelection.
+ *
+ * @param gesture Selection gesture handle (NULL returns GHOSTTY_INVALID_VALUE)
+ * @param terminal Terminal used to interpret and update gesture state
+ * @param event Selection gesture event handle (NULL returns GHOSTTY_INVALID_VALUE)
+ * @param[out] out_selection On success, receives the resulting selection. May
+ *             be NULL to apply the event and discard the selection result.
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_NO_VALUE if the event does not
+ *         currently produce a selection, GHOSTTY_OUT_OF_MEMORY if tracking
+ *         gesture state fails, or GHOSTTY_INVALID_VALUE if gesture, terminal,
+ *         event, or required event data is invalid
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_event(
+                                    GhosttySelectionGesture gesture,
+                                    GhosttyTerminal terminal,
+                                    GhosttySelectionGestureEvent event,
+                                    GhosttySelection* out_selection);
+
+/**
+ * Create a selection gesture object.
+ *
+ * The gesture stores mutable state for terminal text selection gestures. The
+ * gesture is not bound to a terminal at creation time; terminal-dependent APIs
+ * take the terminal explicitly.
+ *
+ * @param allocator Allocator, or NULL for the default allocator
+ * @param out_gesture Receives the created gesture handle
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_INVALID_VALUE if out_gesture is
+ *         NULL, or GHOSTTY_OUT_OF_MEMORY if allocation fails
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_new(
+                                    const GhosttyAllocator* allocator,
+                                    GhosttySelectionGesture* out_gesture);
+
+/**
+ * Free a selection gesture object.
+ *
+ * This releases any tracked terminal references owned by the gesture using the
+ * provided terminal, then frees the gesture object. Passing NULL for gesture is
+ * allowed and is a no-op.
+ *
+ * If the terminal is still alive, pass the terminal most recently used with the
+ * gesture so any tracked terminal references can be released correctly. If the
+ * terminal has already been freed, pass NULL for terminal; the terminal's page
+ * storage has already released the underlying tracked references, so the
+ * gesture wrapper can be safely discarded without touching the stale terminal
+ * state.
+ *
+ * @param gesture Selection gesture handle to free
+ * @param terminal Terminal used to release tracked gesture state, or NULL if
+ *                 the terminal has already been freed
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API void ghostty_selection_gesture_free(
+                                    GhosttySelectionGesture gesture,
+                                    GhosttyTerminal terminal);
+
+/**
+ * Reset any active selection gesture state.
+ *
+ * This cancels the active click sequence and releases any tracked terminal
+ * references owned by the gesture without freeing the gesture object.
+ * Passing NULL is allowed and is a no-op.
+ *
+ * @param gesture Selection gesture handle to reset
+ * @param terminal Terminal used to release tracked gesture state
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API void ghostty_selection_gesture_reset(
+                                    GhosttySelectionGesture gesture,
+                                    GhosttyTerminal terminal);
+
+/**
+ * Read data from a selection gesture.
+ *
+ * The type of value depends on data and is documented by
+ * GhosttySelectionGestureData. For GHOSTTY_SELECTION_GESTURE_DATA_ANCHOR,
+ * the returned GhosttyGridRef is an untracked snapshot with normal grid-ref
+ * lifetime rules.
+ *
+ * @param gesture Selection gesture handle (NULL returns GHOSTTY_INVALID_VALUE)
+ * @param terminal Terminal used to validate terminal-backed gesture state
+ * @param data Data field to read
+ * @param value Output pointer whose type depends on data
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_NO_VALUE if the requested data
+ *         has no value, or GHOSTTY_INVALID_VALUE if gesture, terminal, data, or
+ *         value is invalid
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_get(
+                                    GhosttySelectionGesture gesture,
+                                    GhosttyTerminal terminal,
+                                    GhosttySelectionGestureData data,
+                                    void* value);
+
+/**
+ * Read multiple data fields from a selection gesture in a single call.
+ *
+ * This is an optimization over calling ghostty_selection_gesture_get() multiple
+ * times. Each entry in values must point to storage of the type documented by
+ * the corresponding GhosttySelectionGestureData key.
+ *
+ * If any individual read fails, the function returns that error and writes the
+ * index of the failing key to out_written when out_written is non-NULL. On
+ * success, out_written receives count when non-NULL.
+ *
+ * @param gesture Selection gesture handle (NULL returns GHOSTTY_INVALID_VALUE)
+ * @param terminal Terminal used to validate terminal-backed gesture state
+ * @param count Number of data fields to read
+ * @param keys Data fields to read (must not be NULL)
+ * @param values Output pointers corresponding to keys (must not be NULL)
+ * @param out_written Optional number of fields read, or failing index on error
+ * @return GHOSTTY_SUCCESS on success, GHOSTTY_NO_VALUE if a requested data
+ *         field has no value, or GHOSTTY_INVALID_VALUE if gesture, terminal,
+ *         keys, values, or a value pointer is invalid
+ *
+ * @ingroup selection
+ */
+GHOSTTY_API GhosttyResult ghostty_selection_gesture_get_multi(
+                                    GhosttySelectionGesture gesture,
+                                    GhosttyTerminal terminal,
+                                    size_t count,
+                                    const GhosttySelectionGestureData* keys,
+                                    void** values,
+                                    size_t* out_written);
+
 /**
  * Derive a word selection snapshot from a terminal grid reference.
  *

include/ghostty/vt/types.h

@@ -227,6 +227,38 @@ typedef struct {
   size_t len;
 } GhosttyString;
 
+/**
+ * A surface-space position in pixels.
+ *
+ * This is not a terminal grid coordinate. It represents an x/y position in the
+ * rendered surface coordinate space, with (0, 0) at the top-left of the
+ * surface.
+ */
+typedef struct {
+  /** X position in surface pixels. */
+  double x;
+
+  /** Y position in surface pixels. */
+  double y;
+} GhosttySurfacePosition;
+
+/**
+ * A borrowed list of Unicode scalar values.
+ *
+ * Values are encoded as uint32_t scalar values. The memory is not owned by this
+ * struct. The pointer is only valid for the lifetime documented by the API that
+ * consumes or produces it.
+ *
+ * APIs may document special handling for NULL + len 0, such as “use defaults”.
+ */
+typedef struct {
+  /** Pointer to Unicode scalar values. */
+  const uint32_t* ptr;
+
+  /** Number of entries in ptr. */
+  size_t len;
+} GhosttyCodepoints;
+
 /**
  * Initialize a sized struct to zero and set its size field.
  *

src/lib_vt.zig

@@ -251,6 +251,15 @@ comptime {
         @export(&c.terminal_selection_ordered, .{ .name = "ghostty_terminal_selection_ordered" });
         @export(&c.terminal_selection_contains, .{ .name = "ghostty_terminal_selection_contains" });
         @export(&c.terminal_selection_equal, .{ .name = "ghostty_terminal_selection_equal" });
+        @export(&c.selection_gesture_new, .{ .name = "ghostty_selection_gesture_new" });
+        @export(&c.selection_gesture_free, .{ .name = "ghostty_selection_gesture_free" });
+        @export(&c.selection_gesture_reset, .{ .name = "ghostty_selection_gesture_reset" });
+        @export(&c.selection_gesture_event, .{ .name = "ghostty_selection_gesture_event" });
+        @export(&c.selection_gesture_get, .{ .name = "ghostty_selection_gesture_get" });
+        @export(&c.selection_gesture_get_multi, .{ .name = "ghostty_selection_gesture_get_multi" });
+        @export(&c.selection_gesture_event_new, .{ .name = "ghostty_selection_gesture_event_new" });
+        @export(&c.selection_gesture_event_free, .{ .name = "ghostty_selection_gesture_event_free" });
+        @export(&c.selection_gesture_event_set, .{ .name = "ghostty_selection_gesture_event_set" });
         @export(&c.terminal_grid_ref, .{ .name = "ghostty_terminal_grid_ref" });
         @export(&c.terminal_grid_ref_track, .{ .name = "ghostty_terminal_grid_ref_track" });
         @export(&c.terminal_point_from_grid_ref, .{ .name = "ghostty_terminal_point_from_grid_ref" });

src/terminal/SelectionGesture.zig

@@ -70,6 +70,7 @@ const std = @import("std");
 const assert = std.debug.assert;
 const testing = std.testing;
 const Allocator = std.mem.Allocator;
+const lib = @import("lib.zig");
 const PageList = @import("PageList.zig");
 const Pin = PageList.Pin;
 const Screen = @import("Screen.zig");
@@ -118,22 +119,26 @@ left_drag_autoscroll: Autoscroll,
 ///
 /// This is used to implement selection above/below the viewport that
 /// wants to drag the viewport.
-pub const Autoscroll = enum { none, up, down };
+pub const Autoscroll = lib.Enum(lib.target, &.{
+    "none",
+    "up",
+    "down",
+});
 
 /// The selection behavior for a click and subsequent drag.
-pub const Behavior = enum {
-    /// Cell-granular drag selection. Press returns null to clear selection.
-    cell,
+pub const Behavior = lib.Enum(lib.target, &.{
+    // Cell-granular drag selection. Press returns null to clear selection.
+    "cell",
 
-    /// Word selection on press and word-granular drag selection.
-    word,
+    // Word selection on press and word-granular drag selection.
+    "word",
 
-    /// Line selection on press and line-granular drag selection.
-    line,
+    // Line selection on press and line-granular drag selection.
+    "line",
 
-    /// Semantic command output selection on press and drag.
-    output,
-};
+    // Semantic command output selection on press and drag.
+    "output",
+});
 
 /// Standard terminal selection behavior for single-, double-, and triple-clicks.
 ///

src/terminal/c/main.zig

@@ -31,6 +31,7 @@ pub const modes = @import("modes.zig");
 pub const osc = @import("osc.zig");
 pub const render = @import("render.zig");
 pub const selection = @import("selection.zig");
+pub const selection_gesture = @import("selection_gesture.zig");
 pub const key_event = @import("key_event.zig");
 pub const key_encode = @import("key_encode.zig");
 pub const mouse_event = @import("mouse_event.zig");
@@ -182,6 +183,15 @@ pub const terminal_selection_order = selection.order;
 pub const terminal_selection_ordered = selection.ordered;
 pub const terminal_selection_contains = selection.contains;
 pub const terminal_selection_equal = selection.equal;
+pub const selection_gesture_new = selection_gesture.new;
+pub const selection_gesture_free = selection_gesture.free;
+pub const selection_gesture_reset = selection_gesture.reset;
+pub const selection_gesture_event = selection_gesture.handle_event;
+pub const selection_gesture_get = selection_gesture.get;
+pub const selection_gesture_get_multi = selection_gesture.get_multi;
+pub const selection_gesture_event_new = selection_gesture.event_new;
+pub const selection_gesture_event_free = selection_gesture.event_free;
+pub const selection_gesture_event_set = selection_gesture.event_set;
 pub const terminal_grid_ref = terminal.grid_ref;
 pub const terminal_grid_ref_track = terminal.grid_ref_track;
 pub const terminal_point_from_grid_ref = terminal.point_from_grid_ref;
@@ -214,6 +224,7 @@ test {
     _ = osc;
     _ = render;
     _ = selection;
+    _ = selection_gesture;
     _ = key_event;
     _ = key_encode;
     _ = mouse_event;

src/terminal/c/types.zig

@@ -14,15 +14,29 @@ const size_report = @import("size_report.zig");
 const terminal = @import("terminal.zig");
 const formatter = @import("formatter.zig");
 const selection = @import("selection.zig");
+const selection_gesture = @import("selection_gesture.zig");
 const render = @import("render.zig");
 const style_c = @import("style.zig");
 const mouse_encode = @import("mouse_encode.zig");
 const grid_ref = @import("grid_ref.zig");
 
+/// C: GhosttySurfacePosition
+pub const SurfacePosition = extern struct {
+    x: f64,
+    y: f64,
+};
+
+/// C: GhosttyCodepoints
+pub const Codepoints = extern struct {
+    ptr: ?[*]const u32 = null,
+    len: usize = 0,
+};
+
 /// All C API structs and their Ghostty C names.
 pub const structs: std.StaticStringMap(StructInfo) = structs: {
     @setEvalBranchQuota(10_000);
     break :structs .initComptime(.{
+        .{ "GhosttyCodepoints", StructInfo.init(Codepoints) },
         .{ "GhosttyColorRgb", StructInfo.init(color.RGB.C) },
         .{ "GhosttyDeviceAttributes", StructInfo.init(terminal.DeviceAttributes) },
         .{ "GhosttyDeviceAttributesPrimary", StructInfo.init(terminal.DeviceAttributes.Primary) },
@@ -41,8 +55,11 @@ pub const structs: std.StaticStringMap(StructInfo) = structs: {
         .{ "GhosttyPoint", StructInfo.init(point.Point.C) },
         .{ "GhosttyPointCoordinate", StructInfo.init(point.Coordinate) },
         .{ "GhosttyRenderStateColors", StructInfo.init(render.Colors) },
+        .{ "GhosttySelectionGestureBehaviors", StructInfo.init(selection_gesture.Behaviors) },
+        .{ "GhosttySelectionGestureGeometry", StructInfo.init(selection_gesture.Geometry) },
         .{ "GhosttySizeReportSize", StructInfo.init(size_report.Size) },
         .{ "GhosttyString", StructInfo.init(lib.String) },
+        .{ "GhosttySurfacePosition", StructInfo.init(SurfacePosition) },
         .{ "GhosttyStyle", StructInfo.init(style_c.Style) },
         .{ "GhosttyStyleColor", StructInfo.init(style_c.Color) },
         .{ "GhosttyTerminalOptions", StructInfo.init(terminal.Options) },
@@ -150,6 +167,11 @@ fn jsonWriteAll(writer: *std.Io.Writer) std.Io.Writer.Error!void {
 fn typeName(comptime T: type) []const u8 {
     return switch (@typeInfo(T)) {
         .bool => "bool",
+        .float => |info| switch (info.bits) {
+            32 => "f32",
+            64 => "f64",
+            else => @compileError("unsupported float size"),
+        },
         .int => |info| switch (info.signedness) {
             .signed => switch (info.bits) {
                 8 => "i8",