// Copyright 2020 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.pointerinjector;

using zx;

/// The possible states of a pointer event stream's state machine.
///
/// A typical pointer will move through this state machine:
/// ADD - CHANGE* - REMOVE
enum EventPhase {
    /// The device has started tracking the pointer.
    ADD = 1;

    /// The device has reported an update to the pointer state.
    CHANGE = 2;

    /// The device has stopped tracking the pointer.
    REMOVE = 3;

    /// The event stream is no longer available.
    CANCEL = 4;
};

/// A description of each sampled data point for a pointer device.
/// All fields are required.
table PointerSample {
    /// An identifier of the pointer that issued this event.
    /// It is unique only to a specific pointer device.
    1: uint32 pointer_id;

    /// The state of this event in the pointer event stream's state machine.
    2: EventPhase phase;

    /// The position of this event, in the viewport's coordinate system.
    3: Point2 position_in_viewport;
};

/// A selection of FIFO data sent over the channel.
/// Each data may have a different issuance policy.
flexible union Data {
    /// The parameters of the viewport, sufficient for a client to correctly
    /// interpret the position and scale of pointer events dispatched to it.
    /// - It is issued on every change to the viewport.
    1: Viewport viewport;

    /// A description of each sampled data point in a pointer event stream.
    /// - It is issued on every sample in the pointer event stream.
    2: PointerSample pointer_sample;
};

// A per-device collection of pointer-related data, sent from server to client.
table Event {
    /// The time when this event was observed.
    ///
    /// Required.
    1: zx.time timestamp;

    /// The event's data.
    ///
    /// Required.
    2: Data data;

    /// An identifier to correlate this event's send/receive occurrence across
    /// component boundaries or abstraction layers.
    3: uint64 trace_flow_id;
};