The Perfetto UI can be extended with plugins. These plugins are shipped part of Perfetto.
The guide below explains how to create a plugin for the Perfetto UI.
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
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:
XyzPlugin just Xyz.pluginId and directory name must match.example.com is your domain your plugin should be named com.example.Foo.dev.perfetto.Foo.example.com#DoSomething./ui/run-dev-server
ui/src/plugins/<your-plugin-name>/OWNERS to include your email.hjd@google.com as a reviewer for your CL.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 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 TracePluginContext 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: TracePluginContext): 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 TracePluginContext are removed when the trace is unloaded.
Examples:
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.
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Examples:
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 TracePluginContext object, passing in a migration function.
class MyPlugin implements Plugin { async onTraceLoad(ctx: TracePluginContext): 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:
The plugin interfaces are defined in ui/src/public/index.ts.
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