mojo/services/gfx/images/interfaces/image_pipe.mojom

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module mojo.gfx;

import "geometry/interfaces/geometry.mojom";
import "gfx/images/interfaces/image.mojom";

// The status of the last time this image was presented
enum PresentationStatus {
  PRESENTED = 0,
  // Image properties are not supported by the consumer
  NOT_PRESENTED_INVALID_PROPERTIES = 1,
  // Producer flushed the image pool
  NOT_PRESENTED_FLUSHED = 2,
};

// ImagePipe is a mechanism for streaming shared images between two
// Mojo entities, one of which provides the image contents (the 'producer') and
// one of which does something with the image contents (the 'consumer').
// It operates conceptually on a pool of |Image| objects that the pipe knows
// about, allows image producers to add/remove images to/from this pool, and
// provides mechanisms for the producer and the consumer to negotiate about who
// owns each image in the pool at a given point in time.
interface ImagePipe {

  // Add an image persistently to the pipe's image pool
  // Adding an image that is already added, or using an ID that is already in
  // use are both errors and will cause the connection to close.
  AddImage(Image image, uint32 id);

  // Remove an image from the pipe's pool
  // Use of an invalid ID will cause the connection to close.
  RemoveImage(uint32 id);

  // Mark the image as available for consumption by the consumer
  // The reply will be sent when the consumer is done using this image and
  // is ready to release ownership back to the producer.
  // The reply will not be sent until another Image is presented to replace it
  // presentuing an id that is added will cause the connection to close.
  PresentImage(uint32 id) => (PresentationStatus status);

  // Ask the consumer to release all images in the pipe's pool. This will
  // send the presentation reply with FLUSHED on all images in the pool
  // not being used by the consumer if the consumer is presenting this image,
  // that image may still be presented and its Present reply will reflect that.
  FlushImages();

};