Porting add-ons to Anki 2.1
---------------------------

2.1 is still in alpha and prone to change, so you may wish to wait until it
hits beta before starting to update add-ons. But if you'd like to dive in
straight away, here are some tips on porting.

Python 3
---------

Anki 2.1 requires Python 3.5 or later. After installing Python 3 on your
machine, you can use the 2to3 tool to automatically convert your existing
scripts to Python 3 code on a folder by folder basis, like:

2to3-3.5 --output-dir=aqt3 -W -n aqt
mv aqt aqt-old
mv aqt3 aqt

Most simple code can be converted automatically, but there may be parts of the
code that you need to manually modify.

Qt5 / PyQt5
------------

The syntax for connecting signals and slots has changed in PyQt5. Recent PyQt4
versions support the new syntax as well, so after updating your add-ons you
may find they still work in Anki 2.0.x as well.

More info is available at
http://pyqt.sourceforge.net/Docs/PyQt4/new_style_signals_slots.html

One add-on author reported that the following tool was useful to automatically
convert the code:
https://github.com/rferrazz/pyqt4topyqt5

Compatibility with Anki 2.0
----------------------------

It should be possible for many add-ons to support both Anki 2.0 and 2.1 at the
same time.

Most Python 3 code will run on Python 2 as well, though extra work may be
required when dealing with file access and byte strings.

The Qt modules are in 'PyQt5' instead of 'PyQt4'. You can do a conditional
import, but an easier way is to import from aqt.qt - eg "from aqt.qt import *"

The most difficult part is the change from the unsupported QtWebKit to
QtWebEngine. If you do any non-trivial work with webviews, some work will be
required to port your code to Anki 2.1, and you may find it not worth the effort
of maintaining compatibility with 2.0.

Webview changes
----------------

Qt 5 has dropped WebKit in favour of the Chromium-based WebEngine, so
Anki's webviews are now using WebEngine. Of note:

- WebEngine uses a different method of communicating back to Python.
  AnkiWebView() is a wrapper for webviews which provides a pycmd(str) function in
  Javascript which will call the ankiwebview's onBridgeCmd(str) method. Various
  parts of Anki's UI like reviewer.py and deckbrowser.py have had to be
  modified to use this.
- Javascript is evaluated asynchronously, so if you need the result of a JS
  expression you can use ankiwebview's evalWithCallback().
- As a result of this asynchronous behaviour, editor.saveNow() now requires a
  callback. If your add-on performs actions in the browser, you likely need to
  call editor.saveNow() first and then run the rest of your code in the callback.
  Calls to .onSearch() will need to be changed to .search()/.onSearchActivated()
  as well. See the browser's .deleteNotes() for an example.
- You can now debug the webviews using an external Chrome instance, by setting
  the env var QTWEBENGINE_REMOTE_DEBUGGING to 8080 prior to starting Anki,
  then surfing to localhost:8080 in Chrome.
- Various operations that were supported by WebKit like setScrollPosition() now
need to be implemented in javascript.
- Page actions like mw.web.triggerPageAction(QWebEnginePage.Copy) are also
asynchronous, and need to be rewritten to use javascript or a delay.

Add-ons without a top level file
---------------------------------

Add-ons no longer require a top level file - if you just distribute a single
folder, the folder's __init__.py file will form the entry point. This will not
work in 2.0.x however.

Sharing updated add-ons
------------------------

If you've succeeded in making an add-on that supports both 2.0.x and 2.1.x at
the same time, please feel free to upload it to the shared add-ons area. If
you've decided to make a separate 2.1.x version, it's probably best to just
post a link to it in your current add-on description or upload it separately.
When we get closer to a release I'll look into adding separate uploads for the
two versions.