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// 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 <set>
#include "base/metrics/field_trial_params.h"
#include "base/metrics/histogram_functions.h"
#include "content/renderer/render_frame_impl.h"
#include "third_party/blink/public/web/web_ax_object.h"
#include "third_party/blink/public/web/web_frame.h"
#include "ui/accessibility/ax_error_types.h"
#include "ui/accessibility/ax_tree_update.h"
// Simple macro to make recording histograms easier to read in the code below.
#define RECORD_ERROR(histogram) \
base::UmaHistogramEnumeration(kAXTreeSnapshotterErrorHistogramName, \
AXTreeSnapshotErrorReason::k##histogram)
using ErrorSet = std::set<ui::AXSerializationErrorFlag>;
namespace content {
constexpr char kAXTreeSnapshotterErrorHistogramName[] =
"Accessibility.AXTreeSnapshotter.Snapshot.Error";
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
//
// LINT.IfChange(AXTreeSnapshotErrorReason)
enum class AXTreeSnapshotErrorReason {
kGenericSerializationError = 0,
kNoWebFrame = 1,
kNoActiveDocument = 2,
kNoExistingAXObjectCache = 3,
kSerializeMaxNodesReached = 4,
kSerializeTimeoutReached = 5,
kSerializeMaxNodesAndTimeoutReached = 6,
kMaxValue = kSerializeMaxNodesAndTimeoutReached,
};
// LINT.ThenChange(/tools/metrics/histograms/metadata/accessibility/enums.xml:AXTreeSnapshotErrorReason)
AXTreeSnapshotterImpl::AXTreeSnapshotterImpl(RenderFrameImpl* render_frame,
ui::AXMode ax_mode)
: content::RenderFrameObserver(render_frame), ax_mode_(ax_mode) {
// Do not generate inline textboxes, which are expensive to create and just
// present extra noise to snapshot consumers.
ax_mode.set_mode(ui::AXMode::kInlineTextBoxes, false);
CHECK(render_frame->GetWebFrame());
document_ = render_frame->GetWebFrame()->GetDocument();
}
AXTreeSnapshotterImpl::~AXTreeSnapshotterImpl() = default;
void AXTreeSnapshotterImpl::Snapshot(size_t max_nodes,
base::TimeDelta timeout,
ui::AXTreeUpdate* response) {
base::UmaHistogramBoolean("Accessibility.AXTreeSnapshotter.Snapshot.Request",
true);
if (!render_frame() || !render_frame()->GetWebFrame()) {
RECORD_ERROR(NoWebFrame);
return;
}
if (!document_.IsActive()) {
RECORD_ERROR(NoActiveDocument);
return;
}
SerializeTreeWithLimits(max_nodes, timeout, response);
}
void AXTreeSnapshotterImpl::OnDestruct() {
// Must implement OnDestruct(), but no need to do anything.
}
void AXTreeSnapshotterImpl::SerializeTreeWithLimits(
size_t max_nodes,
base::TimeDelta timeout,
ui::AXTreeUpdate* response) {
ErrorSet out_error;
document_.SnapshotAccessibilityTree(max_nodes, timeout, response, ax_mode_,
&out_error);
ErrorSet::iterator max_nodes_iter =
out_error.find(ui::AXSerializationErrorFlag::kMaxNodesReached);
ErrorSet::iterator timeout_iter =
out_error.find(ui::AXSerializationErrorFlag::kTimeoutReached);
if (max_nodes_iter != out_error.end() && timeout_iter != out_error.end()) {
RECORD_ERROR(SerializeMaxNodesAndTimeoutReached);
} else if (max_nodes_iter != out_error.end()) {
RECORD_ERROR(SerializeMaxNodesReached);
} else if (timeout_iter != out_error.end()) {
RECORD_ERROR(SerializeTimeoutReached);
}
}
} // namespace content
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