chrome-devtools-frontend/front_end/ui/legacy/UIUserMetrics.ts

Chrome DevTools UI

// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Host from '../../core/host/host.js';

export class UIUserMetrics {
  #panelChangedSinceLaunch = false;
  #firedLaunchHistogram = false;
  #launchPanelName = '';

  static #instance: UIUserMetrics|null = null;

  static instance(): UIUserMetrics {
    if (!this.#instance) {
      this.#instance = new UIUserMetrics();
    }
    return this.#instance;
  }

  panelLoaded(panelName: string, histogramName: string): void {
    if (this.#firedLaunchHistogram || panelName !== this.#launchPanelName) {
      return;
    }

    this.#firedLaunchHistogram = true;
    // Use rAF and setTimeout to ensure the marker is fired after layout and rendering.
    // This will give the most accurate representation of the tool being ready for a user.
    requestAnimationFrame(() => {
      setTimeout(() => {
        // Mark the load time so that we can pinpoint it more easily in a trace.
        performance.mark(histogramName);
        // If the user has switched panel before we finished loading, ignore the histogram,
        // since the launch timings will have been affected and are no longer valid.
        if (this.#panelChangedSinceLaunch) {
          return;
        }
        // This fires the event for the appropriate launch histogram.
        // The duration is measured as the time elapsed since the time origin of the document.
        Host.InspectorFrontendHost.InspectorFrontendHostInstance.recordPerformanceHistogram(
            histogramName, performance.now());
      }, 0);
    });
  }

  setLaunchPanel(panelName: string|null): void {
    this.#launchPanelName = (panelName as string);
  }

  performanceTraceLoad(measure: PerformanceMeasure): void {
    Host.InspectorFrontendHost.InspectorFrontendHostInstance.recordPerformanceHistogram(
        'DevTools.TraceLoad', measure.duration);
  }

  panelShown(panelName: string, isLaunching?: boolean): void {
    const code = Host.UserMetrics.PanelCodes[panelName as keyof typeof Host.UserMetrics.PanelCodes] || 0;
    Host.InspectorFrontendHost.InspectorFrontendHostInstance.recordEnumeratedHistogram(
        Host.InspectorFrontendHostAPI.EnumeratedHistogram.PanelShown, code, Host.UserMetrics.PanelCodes.MAX_VALUE);
    Host.InspectorFrontendHost.InspectorFrontendHostInstance.recordUserMetricsAction(
        'DevTools_PanelShown_' + panelName);

    if (!isLaunching) {
      this.#panelChangedSinceLaunch = true;
    }
  }

  settingsPanelShown(settingsViewId: string): void {
    this.panelShown('settings-' + settingsViewId);
  }
}