CaptureTree.cpp

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#include <cassert>
#include <fstream>

#include <capture/CaptureTree.h>
#include <capture/NodeToString.h>
#include <nlohmann/json.hpp>

namespace facebook::yoga {

using namespace nlohmann;

static void captureTree(
    std::string_view serializedTree,
    const std::filesystem::path& path) {
  std::ofstream file(path);
  file << serializedTree;
}

static SerializedMeasureFuncMap& currentSerializedMeasureFuncMap() {
  static thread_local SerializedMeasureFuncMap map{};
  return map;
}

/*
 * Capturing a tree often means that we capturing multiple serial layouts over
 * the course of the capture. Because of this, we need to make sure that we do
 * a full layout pass with no caching. If we do not do this there is a chance
 * we do not capture measure functions that were called and cached in previous
 * layouts. Missing these captures would lead to inaccurate benchmarking where
 * we do not have cached state.
 *
 * TODO: Dirty entire tree not just measure function nodes
 */
static void dirtyTree(YGNodeRef node) {
  if (YGNodeHasMeasureFunc(node)) {
    YGNodeMarkDirty(node);
  }

  const size_t childCount = YGNodeGetChildCount(node);
  for (size_t i = 0; i < childCount; i++) {
    dirtyTree(YGNodeGetChild(node, i));
  }
}

void YGNodeCalculateLayoutWithCapture(
    YGNodeRef node,
    float availableWidth,
    float availableHeight,
    YGDirection ownerDirection,
    const std::filesystem::path& path) {
  dirtyTree(node);
  YGNodeCalculateLayout(node, availableWidth, availableHeight, ownerDirection);

  json j;
  serializeLayoutInputs(j, availableWidth, availableHeight, ownerDirection);
  serializeTree(
      j,
      currentSerializedMeasureFuncMap(),
      node,
      PrintOptions::Style | PrintOptions::Children | PrintOptions::Config |
          PrintOptions::Node);
  // TODO: It is possible to have a measure function call layout again if, e.g.,
  // views are nested in text. Need to be able to resolve this special case.
  currentSerializedMeasureFuncMap().clear();
  captureTree(j.dump(2), path);
}

void captureMeasureFunc(
    YGNodeConstRef node,
    float width,
    YGMeasureMode widthMode,
    float height,
    YGMeasureMode heightMode,
    YGSize output,
    std::chrono::steady_clock::duration durationNs) {
  auto measureFuncIt = currentSerializedMeasureFuncMap().find(node);
  if (measureFuncIt == currentSerializedMeasureFuncMap().end()) {
    std::vector<SerializedMeasureFunc> vec{};
    currentSerializedMeasureFuncMap().insert(std::make_pair(node, vec));
  }
  measureFuncIt = currentSerializedMeasureFuncMap().find(node);
  assert(measureFuncIt != currentSerializedMeasureFuncMap().end());
  measureFuncIt->second.push_back(
      {width,
       widthMode,
       height,
       heightMode,
       output.width,
       output.height,
       durationNs.count()});
}

} // namespace facebook::yoga