App

The App class manages the application lifecycle in Positron.

Import

from positron import App

Creating an App Instance

app = App()

App is a singleton - only one instance can exist per application.

Lifecycle Events

ready

Emitted when Positron has finished initializing.

def on_ready():
    print("App is ready!")

app.on('ready', on_ready)

window-all-closed

Emitted when all windows have been closed.

def on_all_closed():
    app.quit()

app.on('window-all-closed', on_all_closed)

before-quit

Emitted before the application starts closing windows.

def on_before_quit():
    print("App is about to quit")

app.on('before-quit', on_before_quit)

quit

Emitted when the application is quitting.

def on_quit():
    print("App is quitting")

app.on('quit', on_quit)

Methods

app.run()

Starts the application's main event loop.

app.run()

This method blocks until the application quits. Place it at the end of your main script.

app.quit()

Quits the application.

app.quit()

This method:

Emits before-quit event
Closes all windows
Emits quit event
Exits the main loop

app.when_ready(callback)

Convenience method to run a callback when the app is ready.

def create_window():
    win = BrowserWindow({'width': 800, 'height': 600})
    win.load_url('http://localhost:5173')

app.when_ready(create_window)

Equivalent to:

app.on('ready', create_window)

app.on(event, callback)

Parameters:

event (str): Event name
callback (callable): Function to call when event fires

app.on('ready', lambda: print("Ready!"))

Properties

app.windows

List of all BrowserWindow instances.

print(f"Open windows: {len(app.windows)}")

Complete Example

from positron import App, BrowserWindow
from positron.ipc import ipc_main

app = App()

@ipc_main.handle('get-app-info')
def get_app_info(event):
    return {
        'window_count': len(app.windows),
        'version': '1.0.0'
    }

def create_window():
    win = BrowserWindow({
        'width': 1000,
        'height': 700,
        'title': 'My Positron App'
    })
    win.load_url('http://localhost:5173')

def on_window_all_closed():
    print("All windows closed, quitting...")
    app.quit()

def on_before_quit():
    print("Cleaning up before quit...")
    # Perform cleanup here

app.on('window-all-closed', on_window_all_closed)
app.on('before-quit', on_before_quit)

app.when_ready(create_window)
app.run()

Best Practices

Use when_ready for initialization

# ✅ Good
app.when_ready(create_window)
app.run()

# ❌ Bad - window created before app is ready
create_window()
app.run()

Handle window-all-closed

# ✅ Good - app quits when all windows closed
app.on('window-all-closed', lambda: app.quit())

# ❌ Bad - app keeps running with no windows
# (not handling the event)

Use before-quit for cleanup

# ✅ Good
def cleanup():
    # Save state
    # Close database connections
    # Stop background tasks
    pass

app.on('before-quit', cleanup)

Platform Differences

Positron behaves the same across all platforms. Unlike Electron, there's no special macOS behavior where apps stay running after all windows close.

App

App