cef/libcef/common/extensions/api/README.txt
2018-10-25 12:57:05 -04:00

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This directory provides API definitions for CEF. Some extensions are implemented
using Mojo and others use an older JSON-based format.
<api> is the name of the API definition (e.g. 'alarms').
<class> is the name of the class implementation (e.g. 'AlarmManager').
To add a new extension API implemented only in CEF ***:
1. Add libcef/common/extensions/api/<api>.idl or .json file which defines the
API.
2. Add <api>.idl or .json to the 'schema_sources' list in
libcef/common/extensions/api/BUILD.gn. Serialization code will be
generated based on this list in step 4.
3. Add libcef/browser/extensions/api/<api>/<api>_api.[h|cc] class implementation
files and associated entries to the 'libcef_static' target in BUILD.gn.
4. Run the cef_create_projects script and build to generate the
cef/libcef/common/extensions/api/<api>.h file and other serialization code
required by the extensions system.
5. Add an entry in the libcef/common/extensions/api/_*_features.json files if
necessary [1].
6. Add an entry in the libcef/common/extensions/api/*_manifest_overlay.json
files if necessary [2].
7. Call `<class>::GetInstance();` or `<class>Factory::GetFactoryInstance();` [3]
from EnsureBrowserContextKeyedServiceFactoriesBuilt in
libcef/browser/extensions/browser_context_keyed_service_factories.cc.
8. Call `DependsOn(<class>Factory::GetInstance());` from
CefExtensionSystemFactory::CefExtensionSystemFactory in
libcef/browser/extensions/extension_system_factory.cc if necessary [3].
*** Note that CEF does not currently expose its own Mojo APIs. Related code is
commented out in:
cef/BUILD.gn
cef/libcef/common/extensions/api/BUILD.gn
CefExtensionsBrowserClient::RegisterExtensionFunctions
CefExtensionsClient::IsAPISchemaGenerated
CefExtensionsClient::GetAPISchema
To add a new extension API implemented in Chrome:
1. Register the API in libcef/browser/extensions/chrome_api_registration.cc
2. Perform steps 5 through 8 above.
See https://www.chromium.org/developers/design-documents/mojo for more
information.
[1] A feature can optionally express requirements for where it can be accessed.
See the _api_features.json and _permission_features.json files for
additional details. For Chrome extensions this should match the definitions
in the chrome/common/extensions/api/_*_features.json files.
[2] Service Manifest InterfaceProviderSpecs control interfaces exposed between
processes. Mojo interfaces exposed at the frame level are controlled by the
"navigation:frame" dictionary. Those exposed at the process level are
controlled by the "service_manager:connector" dictionary. Failure to specify
this correctly may result in a console error like the following:
InterfaceProviderSpec "navigation:frame" prevented service:
service:content_renderer from binding interface:
mojom::Foo exposed by: service:content_browser
[3] Some Mojo APIs use singleton Factory objects that create a one-to-one
relationship between a service and a BrowserContext. This is used primarily
to control shutdown/destruction order and implementors must explicitly state
which services are depended on. See comments in
components/keyed_service/content/browser_context_keyed_service_factory.h
for additional details.