插件如何增强Anki的JavaScript?

2024-03-29 15:27:22 发布

您现在位置:Python中文网/ 问答频道 /正文

Anki允许卡片使用JavaScript。例如,卡片可以包含以下内容:

<script>
//JavaScript code here
</script>

当显示卡片时,JavaScript代码将被执行。在

为了使这些脚本能够与Anki后端交互(例如,为了更改注释字段的值、添加标记、影响调度等),允许更大的灵活性,我想为Anki(版本2)编写一个插件,它将实现一些后端函数,并使卡的JavaScript脚本能够调用它们。在

例如,假设我的插件中有一个(Python)函数,它与Anki的对象交互:

^{pr2}$

我希望能够允许cards的JavaScript调用该函数,例如在一个card中有这样的内容:

<script>
myFunc(); // This should invoke the plug-in's myFunc().
</script>

我知道如何添加钩子,以便各种Anki事件调用插件的函数,但我希望允许卡中的JavaScript这样做。这到底能做到吗?如果可以,那怎么办?谢谢!在


Tags: 对象函数代码标记版本脚本插件here
1条回答
网友
1楼 · 发布于 2024-03-29 15:27:22

在阅读了@Louis链接的post之后,我与一些同事讨论了这个问题,并尝试了各种各样的方法,我终于想出了一个解决方案:

这个想法可以概括为以下两个要点(和两个次关键点):

  • 插件可以创建一个或多个对象,这些对象将“公开”给cards的JavaScript脚本,这样card脚本就可以访问这些对象——它们的字段和方法——就好像它们是脚本作用域的一部分一样。在

    • 为了做到这一点,对象必须是特定类(或其子类)的实例,并且必须使用适当的PyQt修饰符声明要公开给card脚本的每个方法和属性。在

以及

  • PyQt提供了将此类对象“注入”到webview的功能。在

    • 插件必须确保每次初始化Anki的reviewer的webview时都会发生这种注入。在

下面的代码演示了如何实现这一点。它为卡片脚本提供了一种检查当前状态(“问题”或“答案”)以及访问(读取,更重要的是写入)注释字段的方法。在

from aqt import mw              # Anki's main window object
from aqt import mw QObject      # Our exposed object will be an instance of a subclass of QObject.
from aqt import mw pyqtSlot     # a decorator for exposed methods
from aqt import mw pyqtProperty # a decorator for exposed properties

from anki.hooks import wrap     # We will need this to hook to specific Anki functions in order to make sure the injection happens in time.

# a class whose instance(s) we can expose to card scripts
class CardScriptObject(QObject):
    # some "private" fields - card scripts cannot access these directly 
    _state = None
    _card = None
    _note = None

    # Using pyqtProperty we create a property accessible from the card script.
    # We have to provide the type of the property (in this case str).
    # The second argument is a getter method.
    # This property is read-only. To make it writeable we would add a setter method as a third argument.
    state = pyqtProperty(str, lambda self: self._state)

    # The following methods are exposed to the card script owing to the pyqtSlot decorator.
    # Without it they would be "private".
    @pyqtSlot(str, result = str) # We have to provide the argument type(s) (excluding self),
                                 # as well as the type of the return value - with the named result argument, if a value is to be returned.
    def getField(self, name):
        return self._note[name]

    # Another method, without a return value:
    @pyqtSlot(str, str)
    def setField(self, name, value):
        self._note[name] = value
        self._note.flush()

    # An example of a method that can be invoked with two different signatures -
    # pyqtSlot has to be used for each possible signature:
    # (This method replaces the above two.
    # All three have been included here for the sake of the example.)
    @pyqtSlot(str, result = str)
    @pyqtSlot(str, str)
    def field(self, name, value = None): # sets a field if value given, gets a field otherwise
        if value is None: return self._note[name]
        self._note[name] = value
        self._note.flush()

cardScriptObject = CardScriptObject() # the object to expose to card scripts
flag = None # This flag is used in the injection process, which follows.

# This is a hook to Anki's reviewer's _initWeb method.
# It lets the plug-in know the reviewer's webview is being initialised.
# (It would be too early to perform the injection here, as this method is called before the webview is initialised.
# And it would be too late to do it after _initWeb, as the first card would have already been shown.
# Hence this mechanism.)
def _initWeb():
    global flag
    flag = True

# This is a hook to Anki's reviewer's _showQuestion method.
# It populates our cardScriptObject's "private" fields with the relevant values,
# and more importantly, it exposes ("injects") the object to the webview's JavaScript scope -
# but only if this is the first card since the last initialisation, otherwise the object is already exposed.
def _showQuestion():
    global cardScriptObject, flag
    if flag:
        flag = False
        # The following line does the injection.
        # In this example our cardScriptObject will be accessible from card scripts
        # using the name pluginObject.
        mw.web.page().mainFrame().addToJavaScriptWindowObject("pluginObject", cardScriptObject)
    cardScriptObject._state = "question"
    cardScriptObject._card = mw.reviewer.card
    cardScriptObject._note = mw.reviewer.card.note()

# The following hook to Anki's reviewer's _showAnswer is not necessary for the injection,
# but in this example it serves to update the state.
def _showAnswer():
    global cardScriptObject
    cardScriptObject._state = "answer"

# adding our hooks
# In order to already have our object injected when the first card is shown (so that its scripts can "enjoy" this plug-in),
# and in order for the card scripts to have access to up-to-date information,
# our hooks must be executed _before_ the relevant Anki methods.
mw.reviewer._initWeb = wrap(mw.reviewer._initWeb, _initWeb, "before")
mw.reviewer._showQuestion = wrap(mw.reviewer._showQuestion, _showQuestion, "before")
mw.reviewer._showAnswer = wrap(mw.reviewer._showAnswer, _showAnswer, "before")

就这样!安装了这样一个插件后,从卡中的JavaScript脚本可以使用插件对象状态检查它是作为问题的一部分运行还是作为答案的一部分运行(也可以通过用设置变量的脚本将问题部分包装在答案模板中来实现,但这样更简洁),pluginObject.field(name)从注释中获取字段的值(也可以通过使用Anki的预处理器将字段直接注入JavaScript代码来实现)和pluginObject.field(name,value)设置注释中某个字段的值(据我所知,目前还无法完成)。当然,许多其他功能可以被编程到我们的CardScriptObject中,以允许卡片脚本执行更多操作(读取/更改配置、实现另一个问答机制、与调度器交互等等)。在

如果有人能提出改进的建议,我很想听听。具体来说,我感兴趣的是:

  • 是否有更简洁的方法来公开方法和属性,以允许更大的签名灵活性;以及
  • 是否有一种不那么麻烦的方法来执行注射。在

相关问题 更多 >