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Migration guide

This migration guide will get you through to make your code work with latest CEF Python. This document includes notable changes that were introduced to cefpython and each topic is prefixed with version number in which a change was introduced. This migration guide doesn't cover all changes required for your software to run smoothly. Some changes depend on the GUI framework you are using and this guide doesn't cover these. You will have to go to the examples/ root directory and see the example for your GUI framework. The new examples are very straightforward and include many useful comments explaining whys. You will have to get through its code and see if anything changed that also requires changes in your application.

Table of contents:

v49+ Distribution packages

In latest CEF Python there is only one distribution package available: a wheel package. Wheel packages are distributed on PyPI and you can install it using the pip tool (8.1+ required on Linux). You can also download wheel packages from GitHub Releases.

Windows

On Windows many of the distribution packages such as MSI, EXE, ZIP and InnoSetup files, are no more available. It is too much hassle to support these.

Linux debian package

On Linux the debian package is not supported anymore. Since pip 8.1+ added support for manylinux1 wheel packages, you can now easily install cefpython on Linux using the pip tool. Installing cefpython on Ubuntu using pip should work out of the box, all OS dependencies on Ubuntu should be satisfied by default. However since upstream CEF has OS dependencies that might not be installed by default on other OSes like e.g. Fedora, and since debian packages allow to list these and install in an automated manner, it might be reconsidered in the future to provide debian packages again.

v49+ cefbuilds.com is deprected, use Spotify Automated CEF Builds

The cefbuilds.com site with CEF prebuilt binaries is now deprecated. From now on download prebuilt CEF binaries from the Spotify Automated CEF Builds:

http://opensource.spotify.com/cefbuilds/index.html

v49+ Build instructions and build tools

There were many changes in regards to building CEF and CEF Python. There are now new tools in the tools/ root directory that fully automate building CEF and CEF Python. CEF Python now provides upstream CEF prebuilt binaries and libraries on GitHub Releases tagged eg. "v49-upstream". With these binaries you can build CEF Python from sources in less than 10 minutes. See the new Build instructions document.

v49: GPU acceleration should be disabled on Windows XP

On XP you should disable GPU acceleration by setting the --disable-gpu and --disable-gpu-compositing switches. These switches can be passed programmatically to cef.Initialize, see api/Command Line Switches.

v49 (Win) Handlers' callbacks and other interfaces

In v49.0 release for Windows all handlers' callbacks and other interfaces such as CookieVisitor, StringVisitor and WebRequestClient, are now called using keyword arguments (Issue #291). This will cause many of existing code to break. This is how you should declare callbacks using the new style:

def OnLoadStart(self, browser, **_):
	pass

def OnLoadStart(self, **kwargs):
	browser = kwargs["browser"]

In the first declaration you see that only one argument is declared, the browser, the others unused will be in the "_" variable (the name of the variable is so that PyCharm doesn't warn about unused variable).

Even if you specify and use all arguments, always add the unused kwargs (**_) at the end:

def OnLoadStart(self, browser, frame, **_):
	pass

This will be handy in the future, in a case when upstream CEF adds a new argument to the API, your code won't break. When an argument is removed in upstream CEF API, if it's possible CEF Python will try to keep backward compatibility by emulating behavior of the old argument.

In case of OnLoadStart, when you've used "browser" and "frame" names for the arguments, your code won't break. However in many other callbacks, where you've used argument names that differed from how they were named in API docs, your code will break. Also argument names were changed from camelCase to underscores. For example the OnLoadEnd callback has renamed the httpStatusCode argument to http_code. So in this case your code will definitely break, unless you've also used "http_code" for argument name.

v49+ High DPI support on Windows

It is recommended to embed a DPI awareness manifest in both the main process and the subprocesses (the subprocess.exe executable) instead of calling DpiAware.SetProcessDpiAware which sets DPI awareness only for the main process.

The ApplicationSettings.auto_zooming option has a default value of an empty string now. Previously the default was "system_dpi". When enabling High DPI support you should set it to "system_dpi" explicitilly.

Note that DpiAware.CalculateWindowSize does not handle all DPI settings (e.g. 132% on Windows 10). In newer CEF Python there is available DpiAwareScale which is more reliable and can handle all DPI resolutions. You can copy see its implementation in src/dpi_aware_win.pyx.

v49 (Win) Do not call the 'WindowUtils.OnSize' function

This function can sometimes cause app hanging during window resize. Call instead the new WindowUtils.UpdateBrowserSize function. Except when you use the pywin32.py example, in such case WindowUtils.OnSize must be called. See Issue #464 for more details.

v49+ Notify CEF on move or resize events

It is required to notify the browser on move or resize events so that popup widgets (e.g. <select>) are displayed in the correct location and dismissed when the window moves. Also so that drag & drop areas are updated accordingly. Call Browser.NotifyMoveOrResizeStarted() during a move or resize event in your app window.

v49+ Flash support

See Issue #235 ("Flash support in CEF v49+") for instructions on how to enable Flash.

v49+ Off-screen-rendering: new option "windowless_rendering_enabled"

When using off-screen-rendering you must set the ApplicationSettings "windowless_rendering_enabled" option to True. This applies to examples such as: Kivy, Panda3D, PySDL2 and screenshot example.

API ref: ApplicationSettings.windowless_rendering_enabled

v49+ BrowserSettings options removed

The following options were removed from BrowserSettings:

  • user_style_sheet_location
  • java_disabled
  • accelerated_compositing
  • author_and_user_styles_disabled

v49+ cef.Request.Flags changed

The following flags were removed from cef.Request.Flags:

  • AllowCookies
  • ReportLoadTiming
  • ReportRawHeaders

API ref: Request.GetFlags

v49+ Request.GetHeaderMap and SetHeaderMap change

GetHeaderMap() will not include the Referer value if any and SetHeaderMap() will ignore the Referer value.

API ref: Request.GetHeaderMap

v49+ (Win) HTTPS cache problems on pages with certificate errors

The fix for HTTPS cache problems on pages with certificate errors (and that includes self-signed certificates) is no more applied on Windows.

See Issue #125 for more details.

v50+ Importing the cefpython3 package on Linux

In the past on Linux it was required for the cefpython3 package to be imported before any other packages due to tcmalloc global hook being loaded. This is not required anymore, tcmalloc is disabled by default.

v50+ Install X11 error handlers on Linux

It is required to install X11 error handlers on Linux, otherwise you will see 'BadWindow' errors happening - sometimes randomly - which will cause application to terminate. Since v56+ x11 error handlers are installed automatically by default during the call to cef.Initialize(). However sometimes that is not enough like for example in the wxpython.py example which requires the x11 error handlers to be installed manually after wx was initialized, and that is because wx initialization had reset x11 error handlers that were installed earlier during cef initialization (Issue #334).

You can install X11 error handlers by calling:

WindowUtils = cef.WindowUtils()
WindowUtils.InstallX11ErrorHandlers()

API ref: WindowUtils.InstallX11ErrorHandlers()

v50+ Set window bounds on Linux

It is now required to set window bounds during window "resize", "move" and "configure" events on Linux. You can do so by calling:

browser.SetBounds(x, y, width, height)

API ref: Browser.SetBounds()

v50+ Keyboard focus issues on Linux

There several keyboard focus issues on Linux since CEF library replaced GTK library with X11 library. Most of these issues are fixed in examples by calling SetFocus in LoadHandler.OnLoadStart during initial app loading and/or by calling SetFocus in FocusHandler.OnGotFocus. This keyboard focus issues need to be fixed in usptream CEF. For more details see Issue #284.

v50+ Windows XP and Vista are no more supported

CEF Python v49.0 was the last version to support Windows XP. This is due to Chromium/CEF dropping XP support, last version that supported XP was CEF v49.

v50+ Mac 32-bit is no more supported

CEF Python v31.2 was the last version to support Mac 32-bit. This is due to CEF/Chromium dropping 32-bit support, last version that supported 32-bit was CEF v38.

v51+ Remove LifespanHandler.RunModal

LifespanHandler.RunModal callback is no more available.

v54+ libcef.so library is stripped from symbols on Linux

Symbols useful for debugging are no more available in libcef.so shipped with distribution packages on Linux. This is explained in details in Issue #262.

v55.3+ Handlers' callbacks and other interfaces

Since v55.3 all handlers' callbacks and other interfaces such as CookieVisitor, StringVisitor and WebRequestClient, are now called using keyword arguments (Issue #291). This will cause many of existing code to break. This is how you should declare callbacks using the new style:

def OnLoadStart(self, browser, **_):
	pass

def OnLoadStart(self, **kwargs):
	browser = kwargs["browser"]

In the first declaration you see that only one argument is declared, the browser, the others unused will be in the "_" variable (the name of the variable is so that PyCharm doesn't warn about unused variable).

Even if you specify and use all arguments, always add the unused kwargs (**_) at the end:

def OnLoadStart(self, browser, frame, **_):
	pass

This will be handy in the future, in a case when upstream CEF adds a new argument to the API, your code won't break. When an argument is removed in upstream CEF API, if it's possible CEF Python will try to keep backward compatibility by emulating behavior of the old argument.

In case of OnLoadStart, when you've used "browser" and "frame" names for the arguments, your code won't break. However in many other callbacks, where you've used argument names that differed from how they were named in API docs, your code will break. Also argument names were changed from camelCase to underscores. For example the OnLoadEnd callback has renamed the httpStatusCode argument to http_code. So in this case your code will definitely break, unless you've also used "http_code" for argument name.

v56+ MacOS 10.9+ required to run

CEF v55 was the last version to support MacOS 10.7.

v57.1+ High DPI support on Windows

The cef.DpiAware.SetProcessDpiAware function is now deprecated. Use cef.DpiAware.EnableHighDpiSupport function instead.

The ApplicationSettings.auto_zooming option should have its value set to an empty string (a default now) for High DPI support. In previous versions the default value was "system_dpi" and if you have set it explicitilly in your application, then you should change it to an empty string now.

v66+ Linux patch that fixed HTTPS cache problems on pages with certificate errors was disabled

That patch allowed for HTTPS caching to work when using self-signed certificates (or any invalid certificate). This doesn't work anymore. If you need this feature then you can build from sources and apply the patch yourself. See Issue #125 for more details.

v66+ DisplayHandler.OnConsoleMessage has a new param 'level'

The DisplayHandler.OnConsoleMessage callback has a new param level.

v66+ LifespanHandler.OnBeforePopup is now called on UI thread

The LifespanHandler.OnBeforePopup callback is now called on UI thread. Previously it was called on IO thread.

v66+ RequestHandler.OnBeforeBrowse has a new param 'user_gesture'

The RequestHandler.OnBeforeBrowse callback has a new param user_gesture.

v66+ Window transparency changes

  1. OSR windows (off-screen rendering, also known as windowless) are now transparent by default. You can control its transperency with ApplicationSettings.background_color and BrowserSettings.background_color options. The WindowInfo.SetTransparentPainting method is now deprecated. Calling it with True will do nothing, and calling it with False will result in exception.

  2. It is now possible to have transparent windows also in windowed mode. This seems to be working only on Linux (got it working on Fedora with just a change in window setting).

v66+ BrowserSettings.javascript_open_windows_disallowed option was removed

The BrowserSettings.javascript_open_windows_disallowed option was removed (setting it will do nothing).

v66+ Threads removed: TID_DB, TID_PROCESS_LAUNCHER, TID_CACHE

These threads and their corresponding constants in the cefpython module were removed: TID_DB, TID_PROCESS_LAUNCHER, TID_CACHE.

New threads were added, see cefpython.PostTask description for a complete list of threads.

v66+ cef.Request.Flags changed

Flags removed:

  • AllowCachedCredentials

Flags added:

  • OnlyFromCache
  • AllowStoredCredentials
  • StopOnRedirect

See a complete list of flags in the description of cef.Request.GetFlags method.

v66+ RequestHandler.GetCookieManager not getting called in some cases

In some cases the RequestHandler.GetCookieManager callback is not getting called due to a race condition. This bug is to be fixed in Issue #429.

v66+ Changes to Mac apps that integrate into existing message loop (Qt, wxPython)

In Qt apps calling message loop work in a timer doesn't work anymore. You have to enable external message pump by setting ApplicationSettings.external_message_pump to True. The qt.py example was updated to disable calling message loop work in a timer. External message pump is a recommended way over calling message loop work in a timer on Mac, so this should make Qt apps work smoothly.

In wxPython apps you have to implement both approaches for integrating with existing message loop at the same time:

  1. Call cef.DoMessageLoopWork in a 10ms timer
  2. Set ApplicationSettings.external_message_pump to True

This is not a correct approach and is only a temporary fix for wxPython apps. More testing is required to check if that resolves all the issues with message loop freezing. Only basic testing was performed. It was not tested of how this change affects performance.

See Issue #442 for more details on the issues.

v67+ Do not call the 'WindowUtils.OnSize' function

This function can sometimes cause app hanging during window resize. Call instead the new WindowUtils.UpdateBrowserSize function. Except when you use the pywin32.py example, in such case WindowUtils.OnSize must be called. See Issue #464 for more details.