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API categories | API index

cefpython

Functions in the cefpython module.

Table of contents:

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.

If the url is a local path it needs to start with the file:// prefix. If the url contains special characters it may need proper handling. Starting with v66.1+ it is required for the app code to encode the url properly. You can use the pathlib.PurePath.as_uri in Python 3 or urllib.pathname2url in Python 2 (urllib.request.pathname2url in Python 3) depending on your case.

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.

GetBrowserByIdentifier

Parameter Type
identifier int
Return void

Get browser by identifier. Browser identifier can be obtained by calling Browser.GetIdentifier.

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.

GetDataUrl

Parameter Type
data string
mediatype="html" (optional) string
Return object

Convert data to a Data URL. Only "html" media type is currently supported.

See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URIs

GetGlobalClientCallback

Parameter Type
name string
Return object

Returns a global client callback that was set using SetGlobalClientCallback() or SetGlobalClientHandler. 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.

LoadCrlSetsFile

Parameter Type
path bytes
Return bool

Description from upstream CEF:

Loads the existing "Certificate Revocation Lists" file that is managed by Google Chrome. This file can generally be found in Chrome's User Data directory (e.g. "C:\Users[User]\AppData\Local\Google\Chrome\User Data" on Windows) and is updated periodically by Chrome's component updater service. Must be called in the browser process after the context has been initialized. See https://dev.chromium.org/Home/chromium-security/crlsets for background.

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.

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. Do not perform blocking tasks on this thread. All tasks posted after CefBrowserProcessHandler::OnContextInitialized() and before CefShutdown() are guaranteed to run. This thread will outlive all other CEF threads.
  • cef.TID_FILE (alias cef.TID_FILE_BACKGROUND): Used for blocking tasks (e.g. file system access) where the user won't notice if the task takes an arbitrarily long time to complete. All tasks posted after CefBrowserProcessHandler::OnContextInitialized() and before CefShutdown() are guaranteed to run.
  • cef.TID_FILE_USER_VISIBLE: Used for blocking tasks (e.g. file system access) that affect UI or responsiveness of future user interactions. Do not use if an immediate response to a user interaction is expected. All tasks posted after CefBrowserProcessHandler::OnContextInitialized() and before CefShutdown() are guaranteed to run. Examples:
    • Updating the UI to reflect progress on a long task.
    • Loading data that might be shown in the UI after a future user interaction.
  • cef.TID_FILE_USER_BLOCKING: Used for blocking tasks (e.g. file system access) that affect UI immediately after a user interaction. All tasks posted after CefBrowserProcessHandler::OnContextInitialized() and before CefShutdown() are guaranteed to run. Example: Generating data shown in the UI immediately after a click.
  • cef.TID_IO: Used to process IPC and network messages. Do not perform blocking tasks on this thread. All tasks posted after CefBrowserProcessHandler::OnContextInitialized() and before CefShutdown() are guaranteed to run.

List of threads in the Renderer process:

  • cef.TID_RENDERER: Tasks may be posted to this thread after CefRenderProcessHandler::OnRenderThreadCreated but are not guaranteed to run before sub-process termination (sub-processes may be killed at any time without warning).

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.

SetGlobalClientHandler

Parameter Type
handler object
Return void

Set client handler object (class instance). Its members will be inspected. Private methods that are not meant to be callbacks should have their names prepended with two underscores. Methods with single underscore or no underscore are treated the same as client callbacks.

You can call this method multiple times to set many handlers. For example you can create in your code several objects named AccessibilityHandler, RequestHandler etc.

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().