Embedded WebView2 engine for web links (Windows)
Web links previously launched a separate Chrome/Edge kiosk process, which
caused the whole class of bugs in the tracker: the browser opening behind the
player, being handed off to an already-running instance and exiting instantly,
fighting for foreground/z-order, and leaking msedge.exe/chrome.exe processes
that were never closed.
WebView2 renders as a CHILD HWND of Kivy's own SDL window instead, so there is
no separate top-level browser to open behind the player, nothing to hand the
URL off to, no z-order contest, and no leaked browser process.
Windows/webview2_browser.py
- Environment -> controller -> navigate, driven through pythonnet.
- Async .NET Tasks are polled from Kivy's Clock. Calling GetAwaiter()
.GetResult() would deadlock: the continuation needs the same thread's
message pump.
- The controller is a .NET IntPtr, not a Python int (CreateAsync overloads
do not match otherwise).
- NavigationCompleted is tracked so a page that never loads can be told
apart from one that did. This matters on a closed network: an unreachable
host paints a Chromium error page, and without this the player would show
a blank/error screen for the item's whole slot instead of skipping it.
- is_alive() reports True while starting up. Start-up is async, so a
controller that does not exist yet is not a dead browser; treating it as
one made the first web link after a cold start be skipped instantly.
Windows/webview2_runtime.py
- Detects the Runtime (registry pv value, SDK probe as fallback) and
installs it silently when missing, unelevated, which produces a per-user
install and therefore never raises a UAC prompt on the signage display.
- Success is decided by RE-READING the installed version, not by the
installer exit code: Edge Update returns a non-zero HRESULT
(-2147219416) when the Runtime is already current, which is not a failure.
- On a closed network the online bootstrapper can never succeed, so it fails
fast with an actionable message instead of hanging for the full timeout.
- Failed attempts are cooldown-gated so a broken machine does not re-run an
installer on every start.
Offline hardening
- Browser arguments disable component updates, field trials, safe-browsing
list fetches, translate and other internet chatter. On an isolated LAN
each of those would otherwise have to time out, costing start-up latency.
Pages on the local server are unaffected.
Engine order (best first): WebView2 -> CEF -> Chrome/Edge subprocess. CEF has
no wheels past Python 3.9 so it is dormant on this build; the subprocess engine
remains only as a last resort.
Also fixes the reason the Windows adapters were never used at all:
SignagePlayer.__init__ assigned self.weblink_adapter_factory = None, which
shadowed the CLASS attribute that run_win.py injects. play_weblink() therefore
fell back to the generic adapter, whose find_browser() uses shutil.which() and
finds nothing on Windows because Chrome/Edge are not on PATH. The instance
attribute is now only set when the class attribute is absent.
Verified: windows/test_webview2_embed.py, test_webview2_navigation.py and
test_webview2_offline.py all pass (a locally served page renders with all
internet traffic disabled), and the packaged exe reports
"weblink_launch engine=webview2-embedded" -> "weblink_launched" on every cycle
with no leaked browser processes.
This commit is contained in:
ske087
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"""Closed-network test: does a WebView2 page still load with no internet?
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The signage player lives on an isolated LAN, so the important question is not
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"does example.com load" but "does a page on a reachable *local* host still
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render when there is no internet at all".
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This test simulates that properly:
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1. Start a tiny HTTP server on 127.0.0.1 serving a known marker page.
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2. Create the WebView2 environment **with the same offline browser arguments
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the player uses** (webview2_browser._build_environment_options).
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3. Navigate to the local page and confirm the page's actual content arrives —
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not merely that the controller came up.
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It also blocks real internet resolution for the browser by pointing it at the
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local server only, so a pass here means offline playback genuinely works.
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Run: windows\\venv\\Scripts\\python.exe windows\\test_webview2_offline.py
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Exit code 0 = PASS.
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"""
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import ctypes
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import http.server
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import os
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import socketserver
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import sys
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import threading
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import time
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import urllib.request
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from pathlib import Path
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sys.path.insert(0, str(Path(__file__).resolve().parent))
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MARKER = 'KIWY-OFFLINE-LAN-OK'
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PORT = 18765
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PAGE = f"""<!doctype html>
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<html><head><meta charset="utf-8"><title>pc</title></head>
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<body style="background:#123;color:#fff;font:48px sans-serif">
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<div id="m">{MARKER}</div>
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</body></html>"""
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class _Handler(http.server.BaseHTTPRequestHandler):
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def do_GET(self):
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body = PAGE.encode('utf-8')
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self.send_response(200)
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self.send_header('Content-Type', 'text/html; charset=utf-8')
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self.send_header('Content-Length', str(len(body)))
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self.end_headers()
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self.wfile.write(body)
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def log_message(self, *args):
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pass # keep the test output clean
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def _start_server():
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socketserver.TCPServer.allow_reuse_address = True
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httpd = socketserver.TCPServer(('127.0.0.1', PORT), _Handler)
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thread = threading.Thread(target=httpd.serve_forever, daemon=True)
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thread.start()
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return httpd
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# ── Win32 window (same approach as test_webview2_embed.py) ──────────
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user32 = ctypes.windll.user32
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kernel32 = ctypes.windll.kernel32
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WNDPROC = ctypes.WINFUNCTYPE(
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ctypes.c_int64, ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p, ctypes.c_void_p
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)
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@WNDPROC
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def _wnd_proc(hwnd, msg, wparam, lparam):
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if msg == 0x0002: # WM_DESTROY
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user32.PostQuitMessage(0)
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return 0
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user32.DefWindowProcW.restype = ctypes.c_int64
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user32.DefWindowProcW.argtypes = [
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ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p, ctypes.c_void_p,
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]
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return user32.DefWindowProcW(hwnd, msg, wparam, lparam)
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def _make_window(width=1280, height=720):
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hinstance = kernel32.GetModuleHandleW(None)
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class_name = 'KiwyWebView2OfflineTest'
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class WNDCLASSEX(ctypes.Structure):
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_fields_ = [
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('cbSize', ctypes.c_uint), ('style', ctypes.c_uint),
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('lpfnWndProc', WNDPROC), ('cbClsExtra', ctypes.c_int),
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('cbWndExtra', ctypes.c_int), ('hInstance', ctypes.c_void_p),
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('hIcon', ctypes.c_void_p), ('hCursor', ctypes.c_void_p),
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('hbrBackground', ctypes.c_void_p), ('lpszMenuName', ctypes.c_wchar_p),
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('lpszClassName', ctypes.c_wchar_p), ('hIconSm', ctypes.c_void_p),
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]
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wc = WNDCLASSEX()
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wc.cbSize = ctypes.sizeof(WNDCLASSEX)
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wc.style = 0x0002 | 0x0001
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wc.lpfnWndProc = _wnd_proc
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wc.hInstance = hinstance
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wc.hbrBackground = ctypes.c_void_p(6)
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wc.lpszClassName = class_name
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user32.RegisterClassExW(ctypes.byref(wc))
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hwnd = user32.CreateWindowExW(
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0, class_name, 'Kiwy Offline LAN Test',
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0x00CF0000 | 0x10000000, 60, 60, width, height, 0, 0, hinstance, 0,
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)
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if not hwnd:
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raise RuntimeError('CreateWindowExW failed')
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user32.UpdateWindow(hwnd)
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return hwnd
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def _pump(seconds):
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import ctypes.wintypes as wt
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deadline = time.monotonic() + seconds
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while time.monotonic() < deadline:
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msg = wt.MSG()
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while user32.PeekMessageW(ctypes.byref(msg), None, 0, 0, 1):
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user32.TranslateMessage(ctypes.byref(msg))
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user32.DispatchMessageW(ctypes.byref(msg))
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time.sleep(0.02)
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def main():
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print('=' * 68)
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print(' WebView2 closed-network (LAN-only) test')
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print('=' * 68)
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from webview2_browser import (
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WebView2Browser, _build_environment_options, _offline_browser_arguments,
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)
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if not WebView2Browser.is_available():
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print('FAIL: WebView2 unavailable:', WebView2Browser._import_error)
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return 1
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print('offline browser args:')
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for flag in _offline_browser_arguments().split():
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print(f' {flag}')
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options = _build_environment_options()
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if options is None:
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print('\nFAIL: could not build offline environment options')
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return 1
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print(f'\nAdditionalBrowserArguments set: '
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f'{bool(options.AdditionalBrowserArguments)}')
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httpd = _start_server()
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url = f'http://127.0.0.1:{PORT}/dashboard'
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print(f'\nlocal server: {url}')
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hwnd = _make_window()
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browser = WebView2Browser(hwnd_provider=lambda: hwnd)
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started = time.monotonic()
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if not browser.show(url):
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print('FAIL: show() returned False:', browser.failed_reason)
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httpd.shutdown()
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return 1
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visible = False
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deadline = time.monotonic() + 25
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while time.monotonic() < deadline:
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browser._tick(0)
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_pump(0.1)
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if browser.failed_reason:
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print('FAIL:', browser.failed_reason)
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httpd.shutdown()
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return 1
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if browser.is_showing():
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visible = True
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break
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print(f'page visible : {visible} after {time.monotonic() - started:.1f}s')
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# Confirm the page's REAL CONTENT arrived, not just the controller.
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#
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# NOTE: ExecuteScriptAsync also returns a .NET Task. Calling .Result here
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# would deadlock — the continuation needs this thread's message pump, which
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# is exactly the mistake this file otherwise exists to catch. Poll it while
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# pumping messages instead.
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body = ''
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if visible:
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try:
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task = browser._webview.ExecuteScriptAsync(
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"document.getElementById('m').innerText"
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)
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deadline = time.monotonic() + 10
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while time.monotonic() < deadline:
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_pump(0.05)
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if task.IsCompleted:
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body = task.Result
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break
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except Exception as exc:
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print(f'note: script eval failed ({exc})')
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got_marker = MARKER in (body or '')
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print(f'page content : {"marker found" if got_marker else "MARKER MISSING"} '
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f'({(body or "")[:60]})')
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browser.shutdown()
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httpd.shutdown()
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httpd.server_close()
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ok = visible and got_marker
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print('=' * 68)
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print(' RESULT:', 'PASS' if ok else 'FAIL')
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if ok:
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print(' A local page renders with all internet traffic disabled —')
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print(' web links work on a closed network.')
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print('=' * 68)
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return 0 if ok else 1
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if __name__ == '__main__':
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sys.exit(main())
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Block a user