content/renderer/accessibility/ax_tree_snapshotter_impl.cc

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/renderer/accessibility/ax_tree_snapshotter_impl.h"

#include "content/renderer/render_frame_impl.h"
#include "third_party/blink/public/web/web_ax_context.h"
#include "third_party/blink/public/web/web_ax_object.h"
#include "third_party/blink/public/web/web_document.h"
#include "third_party/blink/public/web/web_frame.h"
#include "ui/accessibility/ax_tree_serializer.h"
#include "ui/accessibility/ax_tree_update.h"

using blink::WebAXContext;
using blink::WebAXObject;
using blink::WebDocument;

namespace content {

AXTreeSnapshotterImpl::AXTreeSnapshotterImpl(RenderFrameImpl* render_frame,
                                             ui::AXMode ax_mode)
    : render_frame_(render_frame) {
  DCHECK(render_frame->GetWebFrame());
  blink::WebDocument document_ = render_frame->GetWebFrame()->GetDocument();
  context_ = std::make_unique<WebAXContext>(document_, ax_mode);
}

AXTreeSnapshotterImpl::~AXTreeSnapshotterImpl() = default;

void AXTreeSnapshotterImpl::Snapshot(size_t max_node_count,
                                     base::TimeDelta timeout,
                                     ui::AXTreeUpdate* response) {
  if (!render_frame_->GetWebFrame())
    return;
  context_->UpdateAXForAllDocuments();

  if (context_->SerializeEntireTree(max_node_count, timeout, response)) {
    return;
  }

  // It failed again. Clear the response object because it might have errors.
  *response = ui::AXTreeUpdate();
  LOG(WARNING) << "Unable to serialize accessibility tree.";

  // As a sanity check, node_id_to_clear and event_from should be uninitialized
  // if this is a full tree snapshot. They'd only be set to something if
  // this was indeed a partial update to the tree (which we don't want).
  DCHECK_EQ(0, response->node_id_to_clear);
  DCHECK_EQ(ax::mojom::EventFrom::kNone, response->event_from);
  DCHECK_EQ(ax::mojom::Action::kNone, response->event_from_action);
}

}  // namespace content