services/semantics/semantics.mojom

// Copyright 2015 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.

[DartPackage="sky_services"]
module semantics;

enum SemanticAction {
  TAP,
  LONG_PRESS,
  SCROLL_LEFT,
  SCROLL_RIGHT,
  SCROLL_UP,
  SCROLL_DOWN,
  INCREASE,
  DECREASE,
};

struct SemanticsNode {
  uint32 id;

  // A null field means "unchanged since last time".
  SemanticFlags? flags;
  SemanticStrings? strings;
  SemanticGeometry? geometry;
  // TODO(abarth): Switch to array<SemanticAction> once that works.
  // See https://github.com/domokit/mojo/issues/799
  array<int32>? actions;
  array<SemanticsNode>? children;
};

struct SemanticFlags {
  // This is intended to just be booleans, so that it can be extended
  // over time yet still be packed tightly.
  bool has_checked_state = false; // whether is_checked is relevant
  bool is_checked = false;
};

struct SemanticStrings {
  // This is intended to just be Strings.
  string label;
};

struct SemanticGeometry {
  // A SemanticsNode defines a rectangle in a cartesian coordinate
  // space within which it is potentially interactive.

  // The transform from the coordinate space of the parent
  // SemanticsNode (or the application's display area, if this is the
  // root node) to this SemanticsNode's coordinate space, described as
  // a 4x4 matrix, with values in column-major order. The array must
  // have exactly 16 values.
  // This can be left unset to imply the identity matrix.
  array<float, 16>? transform;

  // The position and size of the potentially interactive rectangle in the
  // SemanticsNode's coordinate space.
  // If the width or height are zero, then the node should be treated
  // as absent for most purposes. The node may, however, have further
  // children.
  float left;
  float top;
  float width;
  float height;
};

interface SemanticsListener {
  // The engine side, invoked from the app.
  UpdateSemanticsTree(array<SemanticsNode> nodes);
};

[ServiceName="semantics::SemanticsServer"]
interface SemanticsServer {
  // The app side, invoked from the engine.
  AddSemanticsListener(SemanticsListener listener);
  PerformAction(uint32 nodeID, SemanticAction action);
};