"""About:blank watchdog for managing about:blank tabs with DVD screensaver."""
from typing import TYPE_CHECKING, ClassVar
from bubus import BaseEvent
from pydantic import PrivateAttr
from browser_use.browser.events import (
AboutBlankDVDScreensaverShownEvent,
BrowserStopEvent,
BrowserStoppedEvent,
CloseTabEvent,
NavigateToUrlEvent,
TabClosedEvent,
TabCreatedEvent,
)
from browser_use.browser.watchdog_base import BaseWatchdog
if TYPE_CHECKING:
pass
class AboutBlankWatchdog(BaseWatchdog):
"""Ensures there's always exactly one about:blank tab with DVD screensaver."""
# Event contracts
LISTENS_TO: ClassVar[list[type[BaseEvent]]] = [
BrowserStopEvent,
BrowserStoppedEvent,
TabCreatedEvent,
TabClosedEvent,
]
EMITS: ClassVar[list[type[BaseEvent]]] = [
NavigateToUrlEvent,
CloseTabEvent,
AboutBlankDVDScreensaverShownEvent,
]
_stopping: bool = PrivateAttr(default=False)
async def on_BrowserStopEvent(self, event: BrowserStopEvent) -> None:
"""Handle browser stop request - stop creating new tabs."""
# logger.info('[AboutBlankWatchdog] Browser stop requested, stopping tab creation')
self._stopping = True
async def on_BrowserStoppedEvent(self, event: BrowserStoppedEvent) -> None:
"""Handle browser stopped event."""
# logger.info('[AboutBlankWatchdog] Browser stopped')
self._stopping = True
async def on_TabCreatedEvent(self, event: TabCreatedEvent) -> None:
"""Check tabs when a new tab is created."""
# logger.debug(f'[AboutBlankWatchdog] ➕ New tab created: {event.url}')
# If an about:blank tab was created, show DVD screensaver on all about:blank tabs
if event.url == 'about:blank':
await self._show_dvd_screensaver_on_about_blank_tabs()
async def on_TabClosedEvent(self, event: TabClosedEvent) -> None:
"""Check tabs when a tab is closed and proactively create about:blank if needed."""
# logger.debug('[AboutBlankWatchdog] Tab closing, checking if we need to create about:blank tab')
# Don't create new tabs if browser is shutting down
if self._stopping:
# logger.debug('[AboutBlankWatchdog] Browser is stopping, not creating new tabs')
return
# Check if we're about to close the last tab (event happens BEFORE tab closes)
# Use _cdp_get_all_pages for quick check without fetching titles
page_targets = await self.browser_session._cdp_get_all_pages()
if len(page_targets) <= 1:
self.logger.info(
'[AboutBlankWatchdog] Last tab closing, creating new about:blank tab to avoid closing entire browser'
)
# Create the animation tab since no tabs should remain
navigate_event = self.event_bus.dispatch(NavigateToUrlEvent(url='about:blank', new_tab=True))
await navigate_event
# Show DVD screensaver on the new tab
await self._show_dvd_screensaver_on_about_blank_tabs()
else:
# Multiple tabs exist, check after close
await self._check_and_ensure_about_blank_tab()
async def attach_to_target(self, target_id: str) -> None:
"""AboutBlankWatchdog doesn't monitor individual targets."""
pass
async def _check_and_ensure_about_blank_tab(self) -> None:
"""Check current tabs and ensure exactly one about:blank tab with animation exists."""
try:
# For quick checks, just get page targets without titles to reduce noise
page_targets = await self.browser_session._cdp_get_all_pages()
# If no tabs exist at all, create one to keep browser alive
if len(page_targets) == 0:
# Only create a new tab if there are no tabs at all
self.logger.info('[AboutBlankWatchdog] No tabs exist, creating new about:blank DVD screensaver tab')
navigate_event = self.event_bus.dispatch(NavigateToUrlEvent(url='about:blank', new_tab=True))
await navigate_event
# Show DVD screensaver on the new tab
await self._show_dvd_screensaver_on_about_blank_tabs()
# Otherwise there are tabs, don't create new ones to avoid interfering
except Exception as e:
self.logger.error(f'[AboutBlankWatchdog] Error ensuring about:blank tab: {e}')
async def _show_dvd_screensaver_on_about_blank_tabs(self) -> None:
"""Show DVD screensaver on all about:blank pages only."""
try:
# Get just the page targets without expensive title fetching
page_targets = await self.browser_session._cdp_get_all_pages()
browser_session_label = str(self.browser_session.id)[-4:]
for page_target in page_targets:
target_id = page_target['targetId']
url = page_target['url']
# Only target about:blank pages specifically
if url == 'about:blank':
await self._show_dvd_screensaver_loading_animation_cdp(target_id, browser_session_label)
except Exception as e:
self.logger.error(f'[AboutBlankWatchdog] Error showing DVD screensaver: {e}')
async def _show_dvd_screensaver_loading_animation_cdp(self, target_id: str, browser_session_label: str) -> None:
"""
Injects a DVD screensaver-style bouncing logo loading animation overlay into the target using CDP.
This is used to visually indicate that the browser is setting up or waiting.
"""
try:
# Create temporary session for this target without switching focus
temp_session = await self.browser_session.get_or_create_cdp_session(target_id, focus=False)
# Inject the DVD screensaver script (from main branch with idempotency added)
script = f"""
(function(browser_session_label) {{
// Idempotency check
if (window.__dvdAnimationRunning) {{
return; // Already running, don't add another
}}
window.__dvdAnimationRunning = true;
// Ensure document.body exists before proceeding
if (!document.body) {{
// Try again after DOM is ready
window.__dvdAnimationRunning = false; // Reset flag to retry
if (document.readyState === 'loading') {{
document.addEventListener('DOMContentLoaded', () => arguments.callee(browser_session_label));
}}
return;
}}
const animated_title = `Starting agent ${{browser_session_label}}...`;
if (document.title === animated_title) {{
return; // already run on this tab, dont run again
}}
document.title = animated_title;
// Create the main overlay
const loadingOverlay = document.createElement('div');
loadingOverlay.id = 'pretty-loading-animation';
loadingOverlay.style.position = 'fixed';
loadingOverlay.style.top = '0';
loadingOverlay.style.left = '0';
loadingOverlay.style.width = '100vw';
loadingOverlay.style.height = '100vh';
loadingOverlay.style.background = '#000';
loadingOverlay.style.zIndex = '99999';
loadingOverlay.style.overflow = 'hidden';
// Create the image element
const img = document.createElement('img');
img.src = 'https://cf.browser-use.com/logo.svg';
img.alt = 'Browser-Use';
img.style.width = '200px';
img.style.height = 'auto';
img.style.position = 'absolute';
img.style.left = '0px';
img.style.top = '0px';
img.style.zIndex = '2';
img.style.opacity = '0.8';
loadingOverlay.appendChild(img);
document.body.appendChild(loadingOverlay);
// DVD screensaver bounce logic
let x = Math.random() * (window.innerWidth - 300);
let y = Math.random() * (window.innerHeight - 300);
let dx = 1.2 + Math.random() * 0.4; // px per frame
let dy = 1.2 + Math.random() * 0.4;
// Randomize direction
if (Math.random() > 0.5) dx = -dx;
if (Math.random() > 0.5) dy = -dy;
function animate() {{
const imgWidth = img.offsetWidth || 300;
const imgHeight = img.offsetHeight || 300;
x += dx;
y += dy;
if (x <= 0) {{
x = 0;
dx = Math.abs(dx);
}} else if (x + imgWidth >= window.innerWidth) {{
x = window.innerWidth - imgWidth;
dx = -Math.abs(dx);
}}
if (y <= 0) {{
y = 0;
dy = Math.abs(dy);
}} else if (y + imgHeight >= window.innerHeight) {{
y = window.innerHeight - imgHeight;
dy = -Math.abs(dy);
}}
img.style.left = `${{x}}px`;
img.style.top = `${{y}}px`;
requestAnimationFrame(animate);
}}
animate();
// Responsive: update bounds on resize
window.addEventListener('resize', () => {{
x = Math.min(x, window.innerWidth - img.offsetWidth);
y = Math.min(y, window.innerHeight - img.offsetHeight);
}});
// Add a little CSS for smoothness
const style = document.createElement('style');
style.textContent = `
#pretty-loading-animation {{
/*backdrop-filter: blur(2px) brightness(0.9);*/
}}
#pretty-loading-animation img {{
user-select: none;
pointer-events: none;
}}
`;
document.head.appendChild(style);
}})('{browser_session_label}');
"""
await temp_session.cdp_client.send.Runtime.evaluate(params={'expression': script}, session_id=temp_session.session_id)
# No need to detach - session is cached
# Dispatch event
tab_index = await self.browser_session.get_tab_index(target_id)
self.event_bus.dispatch(AboutBlankDVDScreensaverShownEvent(tab_index=tab_index))
except Exception as e:
self.logger.error(f'[AboutBlankWatchdog] Error injecting DVD screensaver: {e}')
