extract-screenshots.js

// Use this on profiles to extract screenshot and arbitrary marker information.
// Example profile: https://perfht.ml/2T7kA2i

function getMarkersByName(thread, name) {
  const { markers, stringTable } = thread;
  const stringIndex = stringTable.indexForString(name);
  const results = [];
  for (let markerIndex = 0; markerIndex < markers.length; markerIndex++) {
    if (markers.name[markerIndex] === stringIndex) {
      results.push({
        data: markers.data[markerIndex],
        time: markers.time[markerIndex]
      });
    }
  }
  return results;
}

{
  var compositorThread = profile.threads.find(thread => thread.name === 'Compositor')
  var contentThreads = profile.threads.filter(
    thread => thread.name === 'GeckoMain' && thread.processType === 'tab'
  );
  // Select whatever events you are interested in, here it's grabbing markers by name.
  var domEvents = contentThreads.map(thread => getMarkersByName(thread, "DOMEvent"))
  // The screenshots contain the "data" payload, which includes the base64 encoded screenshot.
  var screenshots = getMarkersByName(compositorThread, 'CompositorScreenshot')
  console.log({ domEvents, screenshots })
}