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{"version":3,"file":"TBTUtils.js","sourceRoot":"","sources":["../../../../../../../../front_end/models/trace/lantern/metrics/TBTUtils.ts"],"names":[],"mappings":"AAAA,4DAA4D;AAC5D,yEAAyE;AACzE,6BAA6B;AAE7B,MAAM,uBAAuB,GAAG,EAAE,CAAC;AAEnC;;;;;;;;;;;;;;GAcG;AACH,SAAS,0BAA0B,CAC/B,KAAqD,EAAE,WAAmB,EAAE,SAAiB,EAC7F,aAA8D;IAChE,IAAI,SAAS,GAAG,uBAAuB,CAAC;IAExC,gFAAgF;IAChF,qCAAqC;IACrC,EAAE;IACF,mFAAmF;IACnF,0EAA0E;IAC1E,EAAE;IACF,qFAAqF;IACrF,IAAI,aAAa,EAAE,CAAC;QAClB,SAAS,IAAI,CAAC,KAAK,CAAC,QAAQ,GAAG,aAAa,CAAC,QAAQ,CAAC,CAAC;IACzD,CAAC;IAED,IAAI,KAAK,CAAC,QAAQ,GAAG,SAAS,EAAE,CAAC;QAC/B,OAAO,CAAC,CAAC;IACX,CAAC;IACD,IAAI,KAAK,CAAC,GAAG,GAAG,WAAW,EAAE,CAAC;QAC5B,OAAO,CAAC,CAAC;IACX,CAAC;IACD,IAAI,KAAK,CAAC,KAAK,GAAG,SAAS,EAAE,CAAC;QAC5B,OAAO,CAAC,CAAC;IACX,CAAC;IAED,sFAAsF;IACtF,uFAAuF;IACvF,yFAAyF;IACzF,uFAAuF;IACvF,4CAA4C;IAC5C,MAAM,YAAY,GAAG,IAAI,CAAC,GAAG,CAAC,KAAK,CAAC,KAAK,EAAE,WAAW,CAAC,CAAC;IACxD,MAAM,UAAU,GAAG,IAAI,CAAC,GAAG,CAAC,KAAK,CAAC,GAAG,EAAE,SAAS,CAAC,CAAC;IAClD,MAAM,eAAe,GAAG,UAAU,GAAG,YAAY,CAAC;IAClD,IAAI,eAAe,GAAG,SAAS,EAAE,CAAC;QAChC,OAAO,CAAC,CAAC;IACX,CAAC;IAED,OAAO,eAAe,GAAG,SAAS,CAAC;AACrC,CAAC;AAED,SAAS,0BAA0B,CAC/B,cAAqE,EAAE,WAAmB,EAC1F,SAAiB;IACnB,IAAI,SAAS,IAAI,WAAW,EAAE,CAAC;QAC7B,OAAO,CAAC,CAAC;IACX,CAAC;IAED,IAAI,eAAe,GAAG,CAAC,CAAC;IACxB,KAAK,MAAM,KAAK,IAAI,cAAc,EAAE,CAAC;QACnC,eAAe,IAAI,0BAA0B,CAAC,KAAK,EAAE,WAAW,EAAE,SAAS,CAAC,CAAC;IAC/E,CAAC;IAED,OAAO,eAAe,CAAC;AACzB,CAAC;AAED,OAAO,EACL,uBAAuB,EACvB,0BAA0B,EAC1B,0BAA0B,GAC3B,CAAC","sourcesContent":["// Copyright 2024 The Chromium Authors. All rights reserved.\n// Use of this source code is governed by a BSD-style license that can be\n// found in the LICENSE file.\n\nconst BLOCKING_TIME_THRESHOLD = 50;\n\n/**\n * For TBT, We only want to consider tasks that fall in our time range\n * - FCP and TTI for navigation mode\n * - Trace start and trace end for timespan mode\n *\n * FCP is picked as `startTimeMs` because there is little risk of user input happening\n * before FCP so Long Queuing Qelay regions do not harm user experience. Developers should be\n * optimizing to reach FCP as fast as possible without having to worry about task lengths.\n *\n * TTI is picked as `endTimeMs` because we want a well defined end point for page load.\n *\n * @param startTimeMs Should be FCP in navigation mode and the trace start time in timespan mode\n * @param endTimeMs Should be TTI in navigation mode and the trace end time in timespan mode\n * @param topLevelEvent Leave unset if `event` is top level. Has no effect if `event` has the same duration as `topLevelEvent`.\n */\nfunction calculateTbtImpactForEvent(\n    event: {start: number, end: number, duration: number}, startTimeMs: number, endTimeMs: number,\n    topLevelEvent?: {start: number, end: number, duration: number}): number {\n  let threshold = BLOCKING_TIME_THRESHOLD;\n\n  // If a task is not top level, it doesn't make sense to subtract the entire 50ms\n  // blocking threshold from the event.\n  //\n  // e.g. A 80ms top level task with two 40ms children should attribute some blocking\n  // time to the 40ms tasks even though they do not meet the 50ms threshold.\n  //\n  // The solution is to scale the threshold for child events to be considered blocking.\n  if (topLevelEvent) {\n    threshold *= (event.duration / topLevelEvent.duration);\n  }\n\n  if (event.duration < threshold) {\n    return 0;\n  }\n  if (event.end < startTimeMs) {\n    return 0;\n  }\n  if (event.start > endTimeMs) {\n    return 0;\n  }\n\n  // Perform the clipping and then calculate Blocking Region. So if we have a 150ms task\n  // [0, 150] and `startTimeMs` is at 50ms, we first clip the task to [50, 150], and then\n  // calculate the Blocking Region to be [100, 150]. The rational here is that tasks before\n  // the start time are unimportant, so we care whether the main thread is busy more than\n  // 50ms at a time only after the start time.\n  const clippedStart = Math.max(event.start, startTimeMs);\n  const clippedEnd = Math.min(event.end, endTimeMs);\n  const clippedDuration = clippedEnd - clippedStart;\n  if (clippedDuration < threshold) {\n    return 0;\n  }\n\n  return clippedDuration - threshold;\n}\n\nfunction calculateSumOfBlockingTime(\n    topLevelEvents: Array<{start: number, end: number, duration: number}>, startTimeMs: number,\n    endTimeMs: number): number {\n  if (endTimeMs <= startTimeMs) {\n    return 0;\n  }\n\n  let sumBlockingTime = 0;\n  for (const event of topLevelEvents) {\n    sumBlockingTime += calculateTbtImpactForEvent(event, startTimeMs, endTimeMs);\n  }\n\n  return sumBlockingTime;\n}\n\nexport {\n  BLOCKING_TIME_THRESHOLD,\n  calculateSumOfBlockingTime,\n  calculateTbtImpactForEvent,\n};\n"]}