cefpython.md

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cefpython

Functions in the cefpython module.

Table of contents:

• Functions
  • CreateBrowser
  • CreateBrowserSync
  • ExceptHook
  • GetAppSetting
  • GetAppPath
  • GetBrowserByWindowHandle
  • GetCommandLineSwitch
  • GetGlobalClientCallback
  • GetModuleDirectory
  • GetVersion
  • Initialize
  • IsThread
  • MessageLoop
  • MessageLoopWork
  • PostTask
  • PostDelayedTask
  • QuitMessageLoop
  • SetGlobalClientCallback
  • SetOsModalLoop
  • Shutdown

Functions

CreateBrowser

Not yet implemented - currently this method just calls CreateBrowserSync. In upstream CEF this method creates browser asynchronously. Currently CEF Python depends on browser being created synchronously in a few parts of code.

CreateBrowserSync

Parameter	Type
window_info	WindowInfo
settings	BrowserSettings
url	string
window_title	string
Return	Browser

All parameters are optional.

This function can only be called on the UI thread.

The "window_title" parameter will be used only when parent window provided in window_info was set to 0. This is for use with hello_world.py and tutorial.py examples which don't use any third party GUI framework for creation of top-level window.

After the call to CreateBrowserSync() the page is not yet loaded, if you want your next lines of code to do some stuff on the webpage you will have to implement LoadHandler.OnLoadingStateChange callback.

ExceptHook

Parameter	Type
exc_type	-
exc_value	-
exc_trace	-
Return	void

Global except hook to exit app cleanly on error. CEF has a multiprocess architecture and when exiting you need to close all processes (main Browser process, Renderer process, GPU process, etc.) by calling Shutdown(). This hook does the following: in case of exception write it to the "error.log" file, display it to the console, shutdown CEF and exit application immediately by ignoring "finally" (_exit()).

See also Tutorial: Handling Python exceptions.

GetAppSetting

Parameter	Type
key	string
Return	object

Returns ApplicationSettings option that was passed to Initialize(). Returns None if key is not found.

GetAppPath

file_ (optional)	string
Return	string

Get path to where application resides.

GetBrowserByWindowHandle

Parameter	Type
windowHandle	long
Return	void

Get browser by outer or inner window handle. An outer window handle is the one that was passed to CreateBrowserSync(). An inner window handle is a CEF internal window handle.

GetCommandLineSwitch

Parameter	Type
key	string
Return	object

Returns the CommandLineSwitches switch that was passed to Initialize(). Returns None if key is not found.

GetGlobalClientCallback

Parameter	Type
name	string
Return	object

Returns a global client callback that was set using SetGlobalClientCallback(). Returns None if callback was not set.

GetModuleDirectory

Return	string

Get the cefpython module directory. This method is useful to get full path to CEF binaries. This is required when setting ApplicationSettings options like: 'browser_subprocess_path', 'resources_dir_pat' and 'locales_dir_path'.

GetVersion

Return	dict

Return CEF Python and CEF versions dictionary with keys:

• version
• chrome_version
• cef_version
• cef_api_hash_platform
• cef_api_hash_universal
• cef_commit_hash
• cef_commit_number

Initialize

Parameter	Type
settings (optional)	ApplicationSettings
switches (optional)	CommandLineSwitches
Return	bool

This function should be called on the main application thread (UI thread) to initialize CEF when the application is started. A call to Initialize() must have a corresponding call to Shutdown() so that CEF exits cleanly. Otherwise when application closes data (eg. storage, cookies) might not be saved to disk or the process might freeze (experienced on Windows XP).

IsThread

Parameter	Type
threadID	int
Return	bool

Returns true if called on the specified thread.

CEF maintains multiple internal threads that are used for handling different types of tasks. The UI thread creates the browser window and is used for all interaction with the webkit rendering engine and V8 Javascript engine. The UI thread will be the same as the main application thread if CefInitialize() is called with an ApplicationSettings 'multi_threaded_message_loop' option set to false. The IO thread is used for handling schema and network requests. The FILE thread is used for the application cache and other miscellaneous activities.

See PostTask() for a list of threads.

MessageLoop

Return	void

Run the CEF message loop. Use this function instead of an application- provided message loop to get the best balance between performance and CPU usage. This function should only be called on the main application thread (UI thread) and only if cefpython.Initialize() is called with a ApplicationSettings.multi_threaded_message_loop value of false. This function will block until a quit message is received by the system.

See also MessageLoopWork().

MessageLoopWork

Return	void

Call this function in a periodic timer (eg. 10ms).

Description from upstream CEF:

Perform a single iteration of CEF message loop processing. This function is provided for cases where the CEF message loop must be integrated into an existing application message loop. Use of this function is not recommended for most users; use either the CefRunMessageLoop() function or CefSettings.multi_threaded_message_loop if possible. When using this function care must be taken to balance performance against excessive CPU usage. It is recommended to enable the CefSettings.external_message_pump option when using this function so that CefBrowserProcessHandler::OnScheduleMessagePumpWork() callbacks can facilitate the scheduling process. This function should only be called on the main application thread and only if CefInitialize() is called with a CefSettings.multi_threaded_message_loop value of false. This function will not block.

PostTask

Parameter	Type
thread	int
func	object
[args..]	mixed
Return	void

Post a task for execution on the thread associated with this task runner. Execution will occur asynchronously. Only Browser process threads are allowed.

An example usage is in the wxpython.py example on Windows, in implementation of LifespanHandler.OnBeforePopup().

List of threads in the Browser process:

• cef.TID_UI: The main thread in the browser. This will be the same as the main application thread if cefpython.Initialize() is called with a ApplicationSettings.multi_threaded_message_loop value of false.
• cef.TID_DB: Used to interact with the database.
• cef.TID_FILE: Used to interact with the file system.
• cef.TID_FILE_USER_BLOCKING: Used for file system operations that block user interactions. Responsiveness of this thread affects users.
• cef.TID_PROCESS_LAUNCHER: Used to launch and terminate browser processes.
• cef.TID_CACHE: Used to handle slow HTTP cache operations.
• cef.TID_IO: Used to process IPC and network messages.

List of threads in the Renderer process:

• cef.TID_RENDERER: The main thread in the renderer. Used for all webkit and V8 interaction.

PostDelayedTask

Parameter	Type
thread	int
delay_ms	int
func	object
[args..]	mixed
Return	void

Post a task for delayed execution on the specified thread. This function behaves similarly to PostTask above, but with an additional |delay_ms| argument.

QuitMessageLoop

Return	void

Quit the CEF message loop that was started by calling cefpython.MessageLoop(). This function should only be called on the main application thread (UI thread) and only if cefpython.MessageLoop() was used.

SetGlobalClientCallback

Parameter	Type
name	string
callback	function
Return	void

Current CEF Python implementation is limited in handling callbacks that occur during browser creation, in such cases a callback set with Browser.SetClientCallback() or Browser.SetClientHandler() won't work, as this methods can be called only after browser was created. An example of such callback is LifespanHandler.OnAfterCreated().

Some client callbacks are not associated with any browser. In such case use this function instead of the SetClientCallback() and SetClientHandler() Browser methods. An example of such callback is OnCertificateError() in RequestHandler.

Example of using SetGlobalClientCallback() is provided in the wxpython.py example.

SetOsModalLoop

Parameter	Type
modalLoop	bool
Return	void

Set to true before calling Windows APIs like 'TrackPopupMenu' that enter a modal message loop. Set to false after exiting the modal message loop.

Shutdown

Return	void

This function should be called on the main application thread (UI thread) to shut down CEF before the application exits.

You must call this function so that CEF shuts down cleanly. Remember also to delete all CEF browsers references for the browsers to shut down cleanly. For an example see the wxpython.py example MainFrame.OnClose().