public/fidl/fuchsia.ui.sketchy/canvas.fidl

// Copyright 2017 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.sketchy;

using fuchsia.images;

// A Canvas allows clients to draw strokes, which are dynamically tessellated
// and inserted into the global Scenic scene-graph.
[Discoverable]
interface Canvas {
  // Init() must be called once, before invoking any other operations.
  1: Init(CanvasListener? listener);

  // Enqueue a list of operations, which will not take effect until Present() is
  // called.  It is allowable to call Enqueue() several times before calling
  // Present(); the effect is the same as if all operations had been
  // concatenated into a single Enqueue() call.
  //
  // Akin to fuchsia::ui::gfx::Session.Enqueue(); see scenic/session.fidl for details.
  2: Enqueue(vector<Command> commands);

  // Present all previously enqueued operations.  In order to pipeline the
  // preparation of the resources required to render the scene, two lists of
  // fences (implemented as events) are passed.
  //
  // Akin to fuchsia::ui::gfx::Session.Present(); see scenic/session.fidl for details.
  3: Present(uint64 presentation_time) ->
      (fuchsia.images.PresentationInfo presentation_info);
};

// Allows clients to observe canvas events.
interface CanvasListener {
  1: OnError(string description);
  2: OnStrokeFinished(uint32 stroke_id, StrokePath path);
  3: OnPageViewerInvalidated(uint32 viewer_id);
};