Direct control over online/offline status

[magreenblatt]

Original report by me.

---

Original issue 245 created by magreenblatt on 2011-05-24T16:45:12.000Z:

Issue comment 23.4 added support for navigator.onLine and online/offline window events. It would be nice if client applications using features like HTML5 app cache could control online/offline mode directly based on application state information instead of just network status.

[magreenblatt]

Comment 1. originally posted by magreenblatt on 2011-12-15T13:21:55.000Z:

[magreenblatt]

• edited description
• set component to "Framework"

[magreenblatt]

The DevTools network tab has a “Throttling” option which supports modes such as Offline:

This is implemented for DevTools as follows:

1. Browser process DevTools code calls NetworkHandler::SetNetworkConditions which calls NetworkContext::SetNetworkConditions (ThrottlingController::SetConditions) in the network process.
2. ThrottlingController manages the registered state. Only requests that match a frame-specific identifier (devtools_frame_token a.k.a. throttling_profile_id) will be throttled.
3. ScopedThrottlingToken::MaybeCreate (scoped calls to ThrottlingController::RegisterProfileIDForNetLogSource/UnregisterNetLogSource) maps the throttling_profile_id to url_request_->net_log().source().id in the URLLoader constructor.
4. ThrottlingNetworkTransaction::Start (ThrottlingController::GetInterceptor) applies the actual throttling. For example, offline mode causes all requests to fail with net::ERR_INTERNET_DISCONNECTED.
5. Online/offline state needs to be configured separately for ServiceWorkers. See BackgroundSyncRestorer in the DevTools code.
6. Online/offline state in the renderer process (e.g. for navigator.onLine) is configured via InspectorNetworkAgent::emulateNetworkConditions using NetworkStateNotifier::SetNetworkConnectionInfoOverride/ClearOverride and retrieved via NavigatorOnLine.

CEF should support a mode that throttles all requests for the RequestContext (e.g. not requiring the frame-specific identifier).

‌

[magreenblatt]

It might be less complex to handle this through DevToolsAgentHost like in CefDevToolsFrontend::HandleMessageFromDevToolsFrontend (e.g. DevToolsAgentHost::GetOrCreateFor(inspected_contents)->DispatchProtocolMessage).

The message value for offline:

{"id":92,"method":"Network.emulateNetworkConditions","params":{"offline":true,"latency":0,"downloadThroughput":0,"uploadThroughput":0,"connectionType":"none"}}

The message value for online:

{"id":93,"method":"Network.emulateNetworkConditions","params":{"offline":false,"latency":0,"downloadThroughput":0,"uploadThroughput":0}}

DevTools protocol messages are documented at https://chromedevtools.github.io/devtools-protocol/

[magreenblatt]

Changing the network status via the DevTools protocol does not update the UI in an existing DevTools front-end instance. Consequently the best way to test offline mode is by (1) observing that all network requests fail with ERR_INTERNET_DISCONNECTED, and (2) by running javascript:alert(navigator.onLine) from the address bar in cefclient and seeing that it displays false (meaning offline). This mode is per-browser, so a newly created browser will have the default status (e.g. online unless the --offline command-line flag was specified on startup).

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset 39aed35644dc (bb)>>

[magreenblatt]

• changed state from "new" to "resolved"

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset 0fb8a5f1eada (bb)>>

[magreenblatt]

Add support for direct DevTools protocol messaging (fixes issue #2961).

This change allows the client to directly send and receive DevTools
protocol messages (send method calls, and receive method results and
events) without requiring a DevTools front-end or remote-debugging
session.

This change includes additional supporting changes:

• Add a new CefRequestHandler::OnDocumentAvailableInMainFrame
  callback (see issue Add callback for document element creation #1454).
• Add a CefParseJSON variant that accepts a UTF8-encoded buffer.
• Add a --devtools-protocol-log-file=<path> command-line flag for
  logging protocol messages sent to/from the DevTools front-end
  while it is displayed. This is useful for understanding existing
  DevTools protocol usage.
• Add a new "libcef_static_unittests" executable target to support
  light-weight unit tests of libcef_static internals (e.g. without
  requiring exposure via the CEF API). Files to be unittested are
  placed in the new "libcef_static_unittested" source_set which is
  then included by both the existing libcef_static library and the
  new unittests executable target.
• Linux: Remove use_bundled_fontconfig=false, which is no longer
  required and causes unittest build errors (see issue Linux Ubuntu 16.04: Hang during startup in FT_Load_Glyph #2424).

This change also adds a cefclient demo for configuring offline mode
using the DevTools protocol (fixes issue #245). This is controlled
by the "Offline mode" context menu option and the --offline
command-line switch which will launch cefclient in offline mode. When
cefclient is offline all network requests will fail with
ERR_INTERNET_DISCONNECTED and navigator.onLine will return false when
called from JavaScript in any frame. This mode is per-browser so
newly created browser windows will have the default mode. Note that
configuring offline mode in this way will not update the Network tab
UI ("Throtting" option) in a displayed DevTools front-end instance.

→ <<cset fd6631bd1812 (bb)>>