macos: async style clipboard reading

include/ghostty.h

@@ -316,7 +316,7 @@ typedef const ghostty_config_t (*ghostty_runtime_reload_config_cb)(void *);
 typedef void (*ghostty_runtime_set_title_cb)(void *, const char *);
 typedef void (*ghostty_runtime_set_mouse_shape_cb)(void *, ghostty_mouse_shape_e);
 typedef void (*ghostty_runtime_set_mouse_visibility_cb)(void *, bool);
-typedef const char* (*ghostty_runtime_read_clipboard_cb)(void *, ghostty_clipboard_e);
+typedef void (*ghostty_runtime_read_clipboard_cb)(void *, ghostty_clipboard_e, void *);
 typedef void (*ghostty_runtime_write_clipboard_cb)(void *, const char *, ghostty_clipboard_e);
 typedef void (*ghostty_runtime_new_split_cb)(void *, ghostty_split_direction_e, ghostty_surface_config_s);
 typedef void (*ghostty_runtime_new_tab_cb)(void *, ghostty_surface_config_s);
@@ -393,6 +393,7 @@ void ghostty_surface_request_close(ghostty_surface_t);
 void ghostty_surface_split(ghostty_surface_t, ghostty_split_direction_e);
 void ghostty_surface_split_focus(ghostty_surface_t, ghostty_split_focus_direction_e);
 bool ghostty_surface_binding_action(ghostty_surface_t, const char *, uintptr_t);
+void ghostty_surface_complete_clipboard_request(ghostty_surface_t, const char *, uintptr_t, void *);
 
 // APIs I'd like to get rid of eventually but are still needed for now.
 // Don't use these unless you know what you're doing.

macos/Sources/Ghostty/AppState.swift

@@ -72,9 +72,6 @@ extension Ghostty {
             return v;
         }
 
-        /// Cached clipboard string for `read_clipboard` callback.
-        private var cached_clipboard_string: String? = nil
-
         init() {
             // Initialize ghostty global state. This happens once per process.
             guard ghostty_init() == GHOSTTY_SUCCESS else {
@@ -100,7 +97,7 @@ extension Ghostty {
                 set_title_cb: { userdata, title in AppState.setTitle(userdata, title: title) },
                 set_mouse_shape_cb: { userdata, shape in AppState.setMouseShape(userdata, shape: shape) },
                 set_mouse_visibility_cb: { userdata, visible in AppState.setMouseVisibility(userdata, visible: visible) },
-                read_clipboard_cb: { userdata, loc in AppState.readClipboard(userdata, location: loc) },
+                read_clipboard_cb: { userdata, loc, state in AppState.readClipboard(userdata, location: loc, state: state) },
                 write_clipboard_cb: { userdata, str, loc in AppState.writeClipboard(userdata, string: str, location: loc) },
                 new_split_cb: { userdata, direction, surfaceConfig in AppState.newSplit(userdata, direction: direction, config: surfaceConfig) },
                 new_tab_cb: { userdata, surfaceConfig in AppState.newTab(userdata, config: surfaceConfig) },
@@ -301,18 +298,24 @@ extension Ghostty {
             )
         }
 
-        static func readClipboard(_ userdata: UnsafeMutableRawPointer?, location: ghostty_clipboard_e) -> UnsafePointer<CChar>? {
+        static func readClipboard(_ userdata: UnsafeMutableRawPointer?, location: ghostty_clipboard_e, state: UnsafeMutableRawPointer?) {
+            // If we don't even have a surface, something went terrible wrong so we have
+            // to leak "state".
+            guard let surfaceView = self.surfaceUserdata(from: userdata) else { return }
+            guard let surface = surfaceView.surface else { return }
+            
             // We only support the standard clipboard
-            if (location != GHOSTTY_CLIPBOARD_STANDARD) { return nil }
+            if (location != GHOSTTY_CLIPBOARD_STANDARD) {
+                return completeClipboardRequest(surface, data: "", state: state)
+            }
             
-            guard let surface = self.surfaceUserdata(from: userdata) else { return nil }
-            guard let appState = self.appState(fromView: surface) else { return nil }
-            guard let str = NSPasteboard.general.string(forType: .string) else { return nil }
+            // Get our string
+            let str = NSPasteboard.general.string(forType: .string) ?? ""
+            completeClipboardRequest(surface, data: str, state: state)
+        }
         
-            // Ghostty requires we cache the string because the pointer we return has to remain
-            // stable until the next call to readClipboard.
-            appState.cached_clipboard_string = str
-            return (str as NSString).utf8String
+        static private func completeClipboardRequest(_ surface: ghostty_surface_t, data: String, state: UnsafeMutableRawPointer?) {
+            ghostty_surface_complete_clipboard_request(surface, data, UInt(data.count), state)
         }
 
         static func writeClipboard(_ userdata: UnsafeMutableRawPointer?, string: UnsafePointer<CChar>?, location: ghostty_clipboard_e) {

src/apprt/embedded.zig

@@ -58,7 +58,7 @@ pub const App = struct {
         /// Read the clipboard value. The return value must be preserved
         /// by the host until the next call. If there is no valid clipboard
         /// value then this should return null.
-        read_clipboard: *const fn (SurfaceUD, c_int) callconv(.C) ?[*:0]const u8,
+        read_clipboard: *const fn (SurfaceUD, c_int, *apprt.ClipboardRequest) callconv(.C) void,
 
         /// Write the clipboard value.
         write_clipboard: *const fn (SurfaceUD, [*:0]const u8, c_int) callconv(.C) void,
@@ -342,15 +342,25 @@ pub const Surface = struct {
         };
     }
 
-    pub fn getClipboardString(
-        self: *const Surface,
+    pub fn clipboardRequest(
+        self: *Surface,
         clipboard_type: apprt.Clipboard,
-    ) ![:0]const u8 {
-        const ptr = self.app.opts.read_clipboard(
+        state: apprt.ClipboardRequest,
+    ) !void {
+        // We need to allocate to get a pointer to store our clipboard request
+        // so that it is stable until the read_clipboard callback and call
+        // complete_clipboard_request. This sucks but clipboard requests aren't
+        // high throughput so it's probably fine.
+        const alloc = self.app.core_app.alloc;
+        const state_ptr = try alloc.create(apprt.ClipboardRequest);
+        errdefer alloc.destroy(state_ptr);
+        state_ptr.* = state;
+
+        self.app.opts.read_clipboard(
             self.opts.userdata,
             @intCast(@intFromEnum(clipboard_type)),
-        ) orelse return "";
-        return std.mem.sliceTo(ptr, 0);
+            state_ptr,
+        );
     }
 
     pub fn setClipboardString(
@@ -982,6 +992,26 @@ pub const CAPI = struct {
         return true;
     }
 
+    /// Complete a clipboard read request startd via the read callback.
+    /// This can only be called once for a given request. Once it is called
+    /// with a request the request pointer will be invalidated.
+    export fn ghostty_surface_complete_clipboard_request(
+        ptr: *Surface,
+        str_ptr: [*]const u8,
+        str_len: usize,
+        state: *apprt.ClipboardRequest,
+    ) void {
+        // The state is unusable after this
+        defer ptr.core_surface.app.alloc.destroy(state);
+
+        if (str_len == 0) return;
+        const str = str_ptr[0..str_len];
+        ptr.core_surface.completeClipboardRequest(state.*, str) catch |err| {
+            log.err("error completing clipboard request err={}", .{err});
+            return;
+        };
+    }
+
     /// Sets the window background blur on macOS to the desired value.
     /// I do this in Zig as an extern function because I don't know how to
     /// call these functions in Swift.