NF: Improve typing of AnkiWebView action (#3475)

There are only two types of actions. The code does not seems to
consider this to be extandable, and the changed variable is private,
so I would expect it relatively acceptable to change the way it
work. This would improve the typing.

If this is rejected, at least, the callback should be noted as
optional, so that the IDE does not complain that `if cb` can not be
false.

qt/aqt/webview.py

@@ -8,9 +8,9 @@ import json
 import os
 import re
 import sys
-from collections.abc import Callable, Sequence
+from collections.abc import Callable
 from enum import Enum
-from typing import TYPE_CHECKING, Any, cast
+from typing import TYPE_CHECKING, Any, Optional, cast
 
 import anki
 import anki.lang
@@ -285,7 +285,7 @@ class AnkiWebView(QWebEngineView):
         self.onBridgeCmd: Callable[[str], Any] = self.defaultOnBridgeCmd
 
         self._domDone = True
-        self._pendingActions: list[tuple[str, Sequence[Any]]] = []
+        self._pendingActions: list[Callable[[], None]] = []
         self.requiresCol = True
         self.setPage(self._page)
         self._disable_zoom = False
@@ -395,14 +395,13 @@ class AnkiWebView(QWebEngineView):
     def setHtml(  #  type: ignore[override]
         self, html: str, context: PageContext | None = None
     ) -> None:
-        from aqt.mediasrv import PageContext
 
         # discard any previous pending actions
         self._pendingActions = []
         self._domDone = True
         if context is None:
             context = PageContext.UNKNOWN
-        self._queueAction("setHtml", html, context)
+        self._queueAction(lambda: self._setHtml(html, context))
         self.set_open_links_externally(True)
         self.allow_drops = False
         self.show()
@@ -631,10 +630,10 @@ html {{ {font} }}
     def eval(self, js: str) -> None:
         self.evalWithCallback(js, None)
 
-    def evalWithCallback(self, js: str, cb: Callable) -> None:
-        self._queueAction("eval", js, cb)
+    def evalWithCallback(self, js: str, cb: Optional[Callable]) -> None:
+        self._queueAction(lambda: self._evalWithCallback(js, cb))
 
-    def _evalWithCallback(self, js: str, cb: Callable[[Any], Any]) -> None:
+    def _evalWithCallback(self, js: str, cb: Optional[Callable[[Any], Any]]) -> None:
         if cb:
 
             def handler(val: Any) -> None:
@@ -647,22 +646,16 @@ html {{ {font} }}
         else:
             self.page().runJavaScript(js)
 
-    def _queueAction(self, name: str, *args: Any) -> None:
-        self._pendingActions.append((name, args))
+    def _queueAction(self, action: Callable[[], None]) -> None:
+        self._pendingActions.append(action)
         self._maybeRunActions()
 
     def _maybeRunActions(self) -> None:
         if sip.isdeleted(self):
             return
         while self._pendingActions and self._domDone:
-            name, args = self._pendingActions.pop(0)
-
-            if name == "eval":
-                self._evalWithCallback(*args)
-            elif name == "setHtml":
-                self._setHtml(*args)
-            else:
-                raise Exception(f"unknown action: {name}")
+            action = self._pendingActions.pop(0)
+            action()
 
     def _openLinksExternally(self, url: str) -> None:
         openLink(url)