UI plugins

The Perfetto UI can be extended with plugins. These plugins are shipped part of Perfetto.

Create a plugin

The guide below explains how to create a plugin for the Perfetto UI.

Prepare for UI development

First we need to prepare the UI development environment. You will need to use a MacOS or Linux machine. Follow the steps below or see the Getting Started guide for more detail.

git clone https://android.googlesource.com/platform/external/perfetto/ cd perfetto ./tools/install-build-deps --ui

Copy the plugin skeleton

cp -r ui/src/plugins/com.example.Skeleton ui/src/plugins/<your-plugin-name>

Now edit ui/src/plugins/<your-plugin-name>/index.ts. Search for all instances of SKELETON: <instruction> in the file and follow the instructions.

Notes on naming:

Start the dev server

./ui/run-dev-server

Now navigate to

Upload your plugin for review

Plugin extension points

Plugins can extend a handful of specific places in the UI. The sections below show these extension points and give examples of how they can be used.

Commands

Commands are user issuable shortcuts for actions in the UI. They can be accessed via the omnibox.

Follow the create a plugin to get an initial skeleton for your plugin.

To add your first command, add a call to ctx.registerCommand() in either your onActivate() or onTraceLoad() hooks. The recommendation is to register commands in onActivate() by default unless they require something from PluginContextTrace which is not available on PluginContext.

The tradeoff is that commands registered in onTraceLoad() are only available while a trace is loaded, whereas commands registered in onActivate() are available all the time the plugin is active.

class MyPlugin implements Plugin { onActivate(ctx: PluginContext): void { ctx.registerCommand( { id: 'dev.perfetto.ExampleSimpleCommand#LogHelloPlugin', name: 'Log "Hello, plugin!"', callback: () => console.log('Hello, plugin!'), }, ); } onTraceLoad(ctx: PluginContextTrace): void { ctx.registerCommand( { id: 'dev.perfetto.ExampleSimpleTraceCommand#LogHelloTrace', name: 'Log "Hello, trace!"', callback: () => console.log('Hello, trace!'), }, ); } }

Here id is a unique string which identifies this command. The id should be prefixed with the plugin id followed by a #. All command ids must be unique system-wide. name is a human readable name for the command, which is shown in the command palette. Finally callback() is the callback which actually performs the action.

Commands are removed automatically when their context disappears. Commands registered with the PluginContext are removed when the plugin is deactivated, and commands registered with the PluginContextTrace are removed when the trace is unloaded.

Examples:

Hotkeys

A default hotkey may be provided when registering a command.

ctx.registerCommand({ id: 'dev.perfetto.ExampleSimpleCommand#LogHelloWorld', name: 'Log "Hello, World!"', callback: () => console.log('Hello, World!'), defaultHotkey: 'Shift+H', });

Even though the hotkey is a string, it's format checked at compile time using typescript's template literal types.

See hotkey.ts for more details on how the hotkey syntax works, and for the available keys and modifiers.

Tracks

Defining Tracks

Tracks describe how to render a track and how to respond to mouse interaction. However, the interface is a WIP and should be considered unstable. This documentation will be added to over the next few months after the design is finalised.

Reusing Existing Tracks

Creating tracks from scratch is difficult and the API is currently a WIP, so it is strongly recommended to use one of our existing base classes which do a lot of the heavy lifting for you. These base classes also provide a more stable layer between your track and the (currently unstable) track API.

For example, if your track needs to show slices from a given a SQL expression (a very common pattern), extend the NamedSliceTrack abstract base class and implement getSqlSource(), which should return a query with the following columns:

For example, the following track describes a slice track that displays all slices that begin with the letter 'a'.

class MyTrack extends NamedSliceTrack { getSqlSource(): string { return ` SELECT id, ts, dur, depth, name from slice where name like 'a%' `; } }

Registering Tracks

Plugins may register tracks with Perfetto using PluginContextTrace.registerTrack(), usually in their onTraceLoad function.

class MyPlugin implements Plugin { onTraceLoad(ctx: PluginContextTrace): void { ctx.registerTrack({ uri: 'dev.MyPlugin#ExampleTrack', displayName: 'My Example Track', trackFactory: ({trackKey}) => { return new MyTrack({engine: ctx.engine, trackKey}); }, }); } }

Default Tracks

The "default" tracks are a list of tracks that are added to the timeline when a fresh trace is loaded (i.e. not when loading a trace from a permalink). This list is copied into the timeline after the trace has finished loading, at which point control is handed over to the user, allowing them add, remove and reorder tracks as they please. Thus it only makes sense to add default tracks in your plugin's onTraceLoad function, as adding a default track later will have no effect.

class MyPlugin implements Plugin { onTraceLoad(ctx: PluginContextTrace): void { ctx.registerTrack({ // ... as above ... }); ctx.addDefaultTrack({ uri: 'dev.MyPlugin#ExampleTrack', displayName: 'My Example Track', sortKey: PrimaryTrackSortKey.ORDINARY_TRACK, }); } }

Registering and adding a default track is such a common pattern that there is a shortcut for doing both in one go: PluginContextTrace.registerStaticTrack(), which saves having to repeat the URI and display name.

class MyPlugin implements Plugin { onTraceLoad(ctx: PluginContextTrace): void { ctx.registerStaticTrack({ uri: 'dev.MyPlugin#ExampleTrack', displayName: 'My Example Track', trackFactory: ({trackKey}) => { return new MyTrack({engine: ctx.engine, trackKey}); }, sortKey: PrimaryTrackSortKey.COUNTER_TRACK, }); } }

Adding Tracks Directly

Sometimes plugins might want to add a track to the timeline immediately, usually as a result of a command or on some other user action such as a button click. We can do this using PluginContext.timeline.addTrack().

class MyPlugin implements Plugin { onTraceLoad(ctx: PluginContextTrace): void { ctx.registerTrack({ // ... as above ... }); // Register a command that directly adds a new track to the timeline ctx.registerCommand({ id: 'dev.MyPlugin#AddMyTrack', name: 'Add my track', callback: () => { ctx.timeline.addTrack( 'dev.MyPlugin#ExampleTrack', 'My Example Track' ); }, }); } }

Tabs

Tabs are a useful way to display contextual information about the trace, the current selection, or to show the results of an operation.

To register a tab from a plugin, use the PluginContextTrace.registerTab method.

import m from 'mithril'; import {Tab, Plugin, PluginContext, PluginContextTrace} from '../../public'; class MyTab implements Tab { render(): m.Children { return m('div', 'Hello from my tab'); } getTitle(): string { return 'My Tab'; } } class MyPlugin implements Plugin { onActivate(_: PluginContext): void {} async onTraceLoad(ctx: PluginContextTrace): Promise<void> { ctx.registerTab({ uri: 'dev.MyPlugin#MyTab', content: new MyTab(), }); } }

You'll need to pass in a tab-like object, something that implements the Tab interface. Tabs only need to define their title and a render function which specifies how to render the tab.

Registered tabs don't appear immediately - we need to show it first. All registered tabs are displayed in the tab dropdown menu, and can be shown or hidden by clicking on the entries in the drop down menu.

Tabs can also be hidden by clicking the little x in the top right of their handle.

Alternatively, tabs may be shown or hidden programmatically using the tabs API.

ctx.tabs.showTab('dev.MyPlugin#MyTab'); ctx.tabs.hideTab('dev.MyPlugin#MyTab');

Tabs have the following properties:

Ephemeral Tabs

By default, tabs are registered as 'permanent' tabs. These tabs have the following additional properties:

Ephemeral tabs, by contrast, have the following properties:

Ephemeral tabs can be registered by setting the isEphemeral flag when registering the tab.

ctx.registerTab({ isEphemeral: true, uri: 'dev.MyPlugin#MyTab', content: new MyEphemeralTab(), });

Ephemeral tabs are usually added as a result of some user action, such as running a command. Thus, it's common pattern to register a tab and show the tab simultaneously.

Motivating example:

import m from 'mithril'; import {uuidv4} from '../../base/uuid'; import { Plugin, PluginContext, PluginContextTrace, PluginDescriptor, Tab, } from '../../public'; class MyNameTab implements Tab { constructor(private name: string) {} render(): m.Children { return m('h1', `Hello, ${this.name}!`); } getTitle(): string { return 'My Name Tab'; } } class MyPlugin implements Plugin { onActivate(_: PluginContext): void {} async onTraceLoad(ctx: PluginContextTrace): Promise<void> { ctx.registerCommand({ id: 'dev.MyPlugin#AddNewEphemeralTab', name: 'Add new ephemeral tab', callback: () => handleCommand(ctx), }); } } function handleCommand(ctx: PluginContextTrace): void { const name = prompt('What is your name'); if (name) { const uri = 'dev.MyPlugin#MyName' + uuidv4(); // This makes the tab available to perfetto ctx.registerTab({ isEphemeral: true, uri, content: new MyNameTab(name), }); // This opens the tab in the tab bar ctx.tabs.showTab(uri); } } export const plugin: PluginDescriptor = { pluginId: 'dev.MyPlugin', plugin: MyPlugin, };

Details Panels & The Current Selection Tab

The "Current Selection" tab is a special tab that cannot be hidden. It remains permanently in the left-most tab position in the tab bar. Its purpose is to display details about the current selection.

Plugins may register interest in providing content for this tab using the PluginContentTrace.registerDetailsPanel() method.

For example:

class MyPlugin implements Plugin { onActivate(_: PluginContext): void {} async onTraceLoad(ctx: PluginContextTrace): Promise<void> { ctx.registerDetailsPanel({ render(selection: Selection) { if (canHandleSelection(selection)) { return m('div', 'Details for selection'); } else { return undefined; } } }); } }

This function takes an object that implements the DetailsPanel interface, which only requires a render function to be implemented that takes the current selection object and returns either mithril vnodes or a falsy value.

Every render cycle, render is called on all registered details panels, and the first registered panel to return a truthy value will be used.

Currently the winning details panel takes complete control over this tab. Also, the order that these panels are called in is not defined, so if we have multiple details panels competing for the same selection, the one that actually shows up is undefined. This is a limitation of the current approach and will be updated to a more democratic contribution model in the future.

Metric Visualisations

TBD

Examples:

State

NOTE: It is important to consider version skew when using persistent state.

Plugins can persist information into permalinks. This allows plugins to gracefully handle permalinking and is an opt-in - not automatic - mechanism.

Persistent plugin state works using a Store<T> where T is some JSON serializable object. Store is implemented here. Store allows for reading and writing T. Reading:

interface Foo { bar: string; } const store: Store<Foo> = getFooStoreSomehow(); // store.state is immutable and must not be edited. const foo = store.state.foo; const bar = foo.bar; console.log(bar);

Writing:

interface Foo { bar: string; } const store: Store<Foo> = getFooStoreSomehow(); store.edit((draft) => { draft.foo.bar = 'Hello, world!'; }); console.log(store.state.foo.bar); // > Hello, world!

First define an interface for your specific plugin state.

interface MyState { favouriteSlices: MySliceInfo[]; }

To access permalink state, call mountStore() on your PluginContextTrace object, passing in a migration function.

class MyPlugin implements Plugin { async onTraceLoad(ctx: PluginContextTrace): Promise<void> { const store = ctx.mountStore(migrate); } } function migrate(initialState: unknown): MyState { // ... }

When it comes to migration, there are two cases to consider:

In case of a new trace, your migration function is called with undefined. In this case you should return a default version of MyState:

const DEFAULT = {favouriteSlices: []}; function migrate(initialState: unknown): MyState { if (initialState === undefined) { // Return default version of MyState. return DEFAULT; } else { // Migrate old version here. } }

In the permalink case, your migration function is called with the state of the plugin store at the time the permalink was generated. This may be from an older or newer version of the plugin.

Plugins must not make assumptions about the contents of initialState!

In this case you need to carefully validate the state object. This could be achieved in several ways, none of which are particularly straight forward. State migration is difficult!

One brute force way would be to use a version number.

interface MyState { version: number; favouriteSlices: MySliceInfo[]; } const VERSION = 3; const DEFAULT = {favouriteSlices: []}; function migrate(initialState: unknown): MyState { if (initialState && (initialState as {version: any}).version === VERSION) { // Version number checks out, assume the structure is correct. return initialState as State; } else { // Null, undefined, or bad version number - return default value. return DEFAULT; } }

You'll need to remember to update your version number when making changes! Migration should be unit-tested to ensure compatibility.

Examples:

Guide to the plugin API

The plugin interfaces are defined in ui/src/public/index.ts.

Default plugins

TBD

Misc notes