// Copyright 2025 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.ui.display.singleton;

using zx;

@available(added=HEAD)
@discoverable
closed protocol VsyncSource {
    /// Enables or disables receiving `OnVsync` for the given display.
    ///
    /// The client receives `OnVsync` callbacks iff this function is called with `enabled=true`.
    /// Calling this with `enabled=false` stops generating callbacks. Note that there may be a
    /// race with a server receiving this and extra `OnVsync` may be received.
    ///
    /// By default, the listener is assumed to have called `enabled=false`.
    strict SetVsyncEnabled(struct {
        enabled bool;
    });

    /// Notifies the client that a vsync event has occurred.
    strict -> OnVsync(struct {
        /// The time when the VSync occurred.
        ///
        /// The accuracy of this timestamp depends on the display hardware.
        timestamp zx.Time;
    });
};