sdk/platform-tools/systrace/catapult/telemetry/telemetry/web_perf/metrics/jitter_timeline.py

   1 # Copyright 2015 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 from telemetry.value import improvement_direction
   6 from telemetry.value import list_of_scalar_values
   7 from telemetry.web_perf.metrics import timeline_based_metric
   8
   9
  10 JITTER_EVENT_NAME = 'jitter'
  11
  12
  13 class JitterTimelineMetric(timeline_based_metric.TimelineBasedMetric):
  14   """JitterTimelineMetric reports jitter in composited layers.
  15
  16   This jitter is due to the main thread attempting to fix the position of a
  17   scrolling composited layer. 'jitter-amount' is the metric added to the
  18   results.
  19   """
  20
  21   def __init__(self):
  22     super(JitterTimelineMetric, self).__init__()
  23
  24   @staticmethod
  25   def IsJitterEvent(event):
  26     return event.name == JITTER_EVENT_NAME
  27
  28   def AddResults(self, model, renderer_thread, interactions, results):
  29     assert interactions
  30
  31     jitter_events = []
  32     for event in model.IterAllEvents(
  33         event_predicate=self.IsJitterEvent):
  34       jitter_events.append(event)
  35
  36     self._AddJitterResultsInternal(jitter_events, interactions, results)
  37
  38   def _AddJitterResultsInternal(self, events, interactions, results):
  39     jitters = []
  40     for event in events:
  41       if timeline_based_metric.IsEventInInteractions(event, interactions):
  42         jitters.append(event.args['value'])
  43     if jitters:
  44       results.AddValue(list_of_scalar_values.ListOfScalarValues(
  45           page=results.current_page,
  46           tir_label=interactions[0].label,
  47           name='jitter-amount',
  48           units='score',
  49           values=jitters,
  50           description='Jitter each frame',
  51           improvement_direction=improvement_direction.DOWN))