In Qt6 QWebEnginepage and QWebEngineView can be imported separately before constructing the QApplication

src/calibre/ebooks/oeb/polish/check/css.py

@@ -16,7 +16,7 @@ from qt.webengine import (
 from calibre import detect_ncpus as cpu_count, prints
 from calibre.ebooks.oeb.polish.check.base import ERROR, WARN, BaseError
 from calibre.gui2 import must_use_qt
-from calibre.gui2.webengine import secure_webengine
+from calibre.utils.webengine import secure_webengine
 
 
 class CSSParseError(BaseError):

src/calibre/ebooks/pdf/html_writer.py

@@ -31,7 +31,7 @@ from calibre.ebooks.pdf.image_writer import (
 )
 from calibre.ebooks.pdf.render.serialize import PDFStream
 from calibre.gui2 import setup_unix_signals
-from calibre.gui2.webengine import secure_webengine
+from calibre.utils.webengine import secure_webengine
 from calibre.srv.render_book import check_for_maths
 from calibre.utils.fonts.sfnt.container import Sfnt, UnsupportedFont
 from calibre.utils.fonts.sfnt.errors import NoGlyphs

src/calibre/ebooks/render_html.py

@@ -12,7 +12,7 @@ from qt.webengine import QWebEnginePage, QWebEngineScript
 
 from calibre.ebooks.metadata.pdf import page_images
 from calibre.gui2 import must_use_qt
-from calibre.gui2.webengine import secure_webengine
+from calibre.utils.webengine import secure_webengine
 from calibre.utils.filenames import atomic_rename
 from calibre.utils.monotonic import monotonic
 

src/calibre/gui2/toc/location.py

@@ -11,7 +11,7 @@ from qt.webengine import QWebEnginePage, QWebEngineScript, QWebEngineView
 
 from calibre.gui2 import error_dialog, gprefs, is_dark_theme, question_dialog
 from calibre.gui2.palette import dark_color, dark_link_color, dark_text_color
-from calibre.gui2.webengine import secure_webengine
+from calibre.utils.webengine import secure_webengine
 from calibre.utils.logging import default_log
 from calibre.utils.short_uuid import uuid4
 

src/calibre/gui2/tweak_book/preview.py

@@ -33,10 +33,11 @@ from calibre.gui2.palette import dark_color, dark_link_color, dark_text_color
 from calibre.gui2.tweak_book import TOP, actions, current_container, editors, tprefs
 from calibre.gui2.tweak_book.file_list import OpenWithHandler
 from calibre.gui2.viewer.web_view import handle_mathjax_request, send_reply
-from calibre.gui2.webengine import (
+from calibre.utils.webengine import (
-    Bridge, RestartingWebEngineView, create_script, from_js, insert_scripts,
+    Bridge, create_script, from_js, insert_scripts,
     secure_webengine, to_js
 )
+from calibre.gui2.webengine import RestartingWebEngineView
 from calibre.gui2.widgets2 import HistoryLineEdit2
 from calibre.utils.ipc.simple_worker import offload_worker
 from polyglot.builtins import iteritems

src/calibre/gui2/tweak_book/reports.py

@@ -28,7 +28,8 @@ from calibre.ebooks.oeb.polish.report import (
     gather_data, CSSEntry, CSSFileMatch, MatchLocation, ClassEntry,
     ClassFileMatch, ClassElement, CSSRule, LinkLocation)
 from calibre.gui2 import error_dialog, question_dialog, choose_save_file, open_url
-from calibre.gui2.webengine import secure_webengine, RestartingWebEngineView
+from calibre.utils.webengine import secure_webengine
+from calibre.gui2.webengine import RestartingWebEngineView
 from calibre.gui2.tweak_book import current_container, tprefs, dictionaries
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.progress_indicator import ProgressIndicator

src/calibre/gui2/viewer/lookup.py

@@ -18,7 +18,7 @@ from calibre import prints, random_user_agent
 from calibre.constants import cache_dir
 from calibre.gui2 import error_dialog
 from calibre.gui2.viewer.web_view import apply_font_settings, vprefs
-from calibre.gui2.webengine import create_script, insert_scripts, secure_webengine
+from calibre.utils.webengine import create_script, insert_scripts, secure_webengine
 from calibre.gui2.widgets2 import Dialog
 
 vprefs.defaults['lookup_locations'] = [

src/calibre/gui2/viewer/web_view.py

@@ -30,10 +30,11 @@ from calibre.gui2 import choose_images, error_dialog, safe_open_url, config
 from calibre.gui2.viewer import link_prefix_for_location_links, performance_monitor
 from calibre.gui2.viewer.config import viewer_config_dir, vprefs
 from calibre.gui2.viewer.tts import TTS
-from calibre.gui2.webengine import (
+from calibre.utils.webengine import (
-    Bridge, RestartingWebEngineView, create_script, from_js, insert_scripts,
+    Bridge, create_script, from_js, insert_scripts,
     secure_webengine, to_js
 )
+from calibre.gui2.webengine import RestartingWebEngineView
 from calibre.srv.code import get_translations_data
 from calibre.utils.localization import localize_user_manual_link
 from calibre.utils.serialize import json_loads

src/calibre/gui2/webengine.py

@@ -1,140 +1,11 @@
 #!/usr/bin/env python
 # License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
 
-
+from qt.core import Qt, pyqtSignal
-import json
+from qt.webengine import QWebEnginePage, QWebEngineView
-
-from qt.core import QObject, Qt, pyqtSignal
-from qt.webengine import QWebEnginePage, QWebEngineScript, QWebEngineView, QWebEngineSettings
 
 from calibre import prints
 from calibre.utils.monotonic import monotonic
-from calibre.utils.rapydscript import special_title
-from polyglot.builtins import iteritems
-
-
-def secure_webengine(view_or_page_or_settings, for_viewer=False):
-    s = view_or_page_or_settings.settings() if hasattr(
-        view_or_page_or_settings, 'settings') else view_or_page_or_settings
-    a = s.setAttribute
-    a(QWebEngineSettings.WebAttribute.PluginsEnabled, False)
-    if not for_viewer:
-        a(QWebEngineSettings.WebAttribute.JavascriptEnabled, False)
-        s.setUnknownUrlSchemePolicy(QWebEngineSettings.UnknownUrlSchemePolicy.DisallowUnknownUrlSchemes)
-        if hasattr(view_or_page_or_settings, 'setAudioMuted'):
-            view_or_page_or_settings.setAudioMuted(True)
-    a(QWebEngineSettings.WebAttribute.JavascriptCanOpenWindows, False)
-    a(QWebEngineSettings.WebAttribute.JavascriptCanAccessClipboard, False)
-    # ensure javascript cannot read from local files
-    a(QWebEngineSettings.WebAttribute.LocalContentCanAccessFileUrls, False)
-    a(QWebEngineSettings.WebAttribute.AllowWindowActivationFromJavaScript, False)
-    return s
-
-
-def insert_scripts(profile, *scripts):
-    sc = profile.scripts()
-    for script in scripts:
-        for existing in sc.find(script.name()):
-            sc.remove(existing)
-    for script in scripts:
-        sc.insert(script)
-
-
-def create_script(
-    name, src, world=QWebEngineScript.ScriptWorldId.ApplicationWorld,
-    injection_point=QWebEngineScript.InjectionPoint.DocumentReady,
-    on_subframes=True
-):
-    script = QWebEngineScript()
-    if isinstance(src, bytes):
-        src = src.decode('utf-8')
-    script.setSourceCode(src)
-    script.setName(name)
-    script.setWorldId(world)
-    script.setInjectionPoint(injection_point)
-    script.setRunsOnSubFrames(on_subframes)
-    return script
-
-
-from_js = pyqtSignal
-
-
-class to_js(str):
-
-    def __call__(self, *a):
-        prints(f'WARNING: Calling {self.name}() before the javascript bridge is ready')
-    emit = __call__
-
-
-class to_js_bound(QObject):
-
-    def __init__(self, bridge, name):
-        QObject.__init__(self, bridge)
-        self.name = name
-
-    def __call__(self, *args):
-        self.parent().page.runJavaScript('if (window.python_comm) python_comm._from_python({}, {})'.format(
-            json.dumps(self.name), json.dumps(args)), QWebEngineScript.ScriptWorldId.ApplicationWorld)
-    emit = __call__
-
-
-class Bridge(QObject):
-
-    bridge_ready = pyqtSignal()
-
-    def __init__(self, page):
-        QObject.__init__(self, page)
-        self._signals = json.dumps(tuple({k for k, v in iteritems(self.__class__.__dict__) if isinstance(v, pyqtSignal)}))
-        self._signals_registered = False
-        page.titleChanged.connect(self._title_changed)
-        for k, v in iteritems(self.__class__.__dict__):
-            if isinstance(v, to_js):
-                v.name = k
-
-    @property
-    def page(self):
-        return self.parent()
-
-    @property
-    def ready(self):
-        return self._signals_registered
-
-    def _title_changed(self, title):
-        if title.startswith(special_title):
-            self._poll_for_messages()
-
-    def _register_signals(self):
-        self._signals_registered = True
-        for k, v in iteritems(self.__class__.__dict__):
-            if isinstance(v, to_js):
-                setattr(self, k, to_js_bound(self, k))
-        self.page.runJavaScript('python_comm._register_signals(' + self._signals + ')', QWebEngineScript.ScriptWorldId.ApplicationWorld)
-        self.bridge_ready.emit()
-
-    def _poll_for_messages(self):
-        self.page.runJavaScript('python_comm._poll()', QWebEngineScript.ScriptWorldId.ApplicationWorld, self._dispatch_messages)
-
-    def _dispatch_messages(self, messages):
-        try:
-            for msg in messages:
-                if isinstance(msg, dict):
-                    mt = msg.get('type')
-                    if mt == 'signal':
-                        signal = getattr(self, msg['name'], None)
-                        if signal is None:
-                            prints('WARNING: No js-to-python signal named: ' + msg['name'])
-                        else:
-                            args = msg['args']
-                            if args:
-                                signal.emit(*args)
-                            else:
-                                signal.emit()
-                    elif mt == 'qt-ready':
-                        self._register_signals()
-        except Exception:
-            if messages:
-                import traceback
-                traceback.print_exc()
 
 
 class RestartingWebEngineView(QWebEngineView):
@@ -161,29 +32,3 @@ class RestartingWebEngineView(QWebEngineView):
             self._last_reload_at = monotonic()
             self.render_process_restarted.emit()
             prints('Restarting Qt WebEngine')
-
-
-if __name__ == '__main__':
-    from calibre.gui2 import Application
-    from calibre.gui2.tweak_book.preview import WebPage
-    from qt.core import QMainWindow
-    app = Application([])
-    view = QWebEngineView()
-    page = WebPage(view)
-    view.setPage(page)
-    w = QMainWindow()
-    w.setCentralWidget(view)
-
-    class Test(Bridge):
-        s1 = from_js(object)
-        j1 = to_js()
-    t = Test(view.page())
-    t.s1.connect(print)
-    w.show()
-    view.setHtml('''
-<p>hello</p>
-    ''')
-    app.exec()
-    del t
-    del page
-    del app

src/calibre/utils/rapydscript.py

@@ -59,7 +59,7 @@ def compiler():
 
     from calibre import walk
     from calibre.gui2 import must_use_qt
-    from calibre.gui2.webengine import secure_webengine
+    from calibre.utils.webengine import secure_webengine
     must_use_qt()
 
     with lzma.open(P(COMPILER_PATH, allow_user_override=False)) as lzf:
@@ -340,7 +340,7 @@ def run_rapydscript_tests():
     from calibre.constants import FAKE_HOST, FAKE_PROTOCOL
     from calibre.gui2 import must_use_qt
     from calibre.gui2.viewer.web_view import send_reply
-    from calibre.gui2.webengine import secure_webengine, insert_scripts, create_script
+    from calibre.utils.webengine import secure_webengine, insert_scripts, create_script
     must_use_qt()
     scheme = QWebEngineUrlScheme(FAKE_PROTOCOL.encode('ascii'))
     scheme.setSyntax(QWebEngineUrlScheme.Syntax.Host)

src/calibre/utils/webengine.py

@@ -0,0 +1,134 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2021, Kovid Goyal <kovid at kovidgoyal.net>
+
+
+import json
+from qt.core import QObject, pyqtSignal
+from qt.webengine import QWebEngineScript, QWebEngineSettings
+
+from calibre.utils.rapydscript import special_title
+
+
+def secure_webengine(view_or_page_or_settings, for_viewer=False):
+    s = view_or_page_or_settings.settings() if hasattr(
+        view_or_page_or_settings, 'settings') else view_or_page_or_settings
+    a = s.setAttribute
+    a(QWebEngineSettings.WebAttribute.PluginsEnabled, False)
+    if not for_viewer:
+        a(QWebEngineSettings.WebAttribute.JavascriptEnabled, False)
+        s.setUnknownUrlSchemePolicy(QWebEngineSettings.UnknownUrlSchemePolicy.DisallowUnknownUrlSchemes)
+        if hasattr(view_or_page_or_settings, 'setAudioMuted'):
+            view_or_page_or_settings.setAudioMuted(True)
+    a(QWebEngineSettings.WebAttribute.JavascriptCanOpenWindows, False)
+    a(QWebEngineSettings.WebAttribute.JavascriptCanAccessClipboard, False)
+    # ensure javascript cannot read from local files
+    a(QWebEngineSettings.WebAttribute.LocalContentCanAccessFileUrls, False)
+    a(QWebEngineSettings.WebAttribute.AllowWindowActivationFromJavaScript, False)
+    return s
+
+
+def insert_scripts(profile, *scripts):
+    sc = profile.scripts()
+    for script in scripts:
+        for existing in sc.find(script.name()):
+            sc.remove(existing)
+    for script in scripts:
+        sc.insert(script)
+
+
+def create_script(
+    name, src, world=QWebEngineScript.ScriptWorldId.ApplicationWorld,
+    injection_point=QWebEngineScript.InjectionPoint.DocumentReady,
+    on_subframes=True
+):
+    script = QWebEngineScript()
+    if isinstance(src, bytes):
+        src = src.decode('utf-8')
+    script.setSourceCode(src)
+    script.setName(name)
+    script.setWorldId(world)
+    script.setInjectionPoint(injection_point)
+    script.setRunsOnSubFrames(on_subframes)
+    return script
+
+
+from_js = pyqtSignal
+
+
+class to_js(str):
+
+    def __call__(self, *a):
+        print(f'WARNING: Calling {self.name}() before the javascript bridge is ready')
+    emit = __call__
+
+
+class to_js_bound(QObject):
+
+    def __init__(self, bridge, name):
+        QObject.__init__(self, bridge)
+        self.name = name
+
+    def __call__(self, *args):
+        self.parent().page.runJavaScript('if (window.python_comm) python_comm._from_python({}, {})'.format(
+            json.dumps(self.name), json.dumps(args)), QWebEngineScript.ScriptWorldId.ApplicationWorld)
+    emit = __call__
+
+
+class Bridge(QObject):
+
+    bridge_ready = pyqtSignal()
+
+    def __init__(self, page):
+        QObject.__init__(self, page)
+        self._signals = json.dumps(tuple({k for k, v in self.__class__.__dict__.items() if isinstance(v, pyqtSignal)}))
+        self._signals_registered = False
+        page.titleChanged.connect(self._title_changed)
+        for k, v in self.__class__.__dict__.items():
+            if isinstance(v, to_js):
+                v.name = k
+
+    @property
+    def page(self):
+        return self.parent()
+
+    @property
+    def ready(self):
+        return self._signals_registered
+
+    def _title_changed(self, title):
+        if title.startswith(special_title):
+            self._poll_for_messages()
+
+    def _register_signals(self):
+        self._signals_registered = True
+        for k, v in self.__class__.__dict__.items():
+            if isinstance(v, to_js):
+                setattr(self, k, to_js_bound(self, k))
+        self.page.runJavaScript('python_comm._register_signals(' + self._signals + ')', QWebEngineScript.ScriptWorldId.ApplicationWorld)
+        self.bridge_ready.emit()
+
+    def _poll_for_messages(self):
+        self.page.runJavaScript('python_comm._poll()', QWebEngineScript.ScriptWorldId.ApplicationWorld, self._dispatch_messages)
+
+    def _dispatch_messages(self, messages):
+        try:
+            for msg in messages:
+                if isinstance(msg, dict):
+                    mt = msg.get('type')
+                    if mt == 'signal':
+                        signal = getattr(self, msg['name'], None)
+                        if signal is None:
+                            print('WARNING: No js-to-python signal named: ' + msg['name'])
+                        else:
+                            args = msg['args']
+                            if args:
+                                signal.emit(*args)
+                            else:
+                                signal.emit()
+                    elif mt == 'qt-ready':
+                        self._register_signals()
+        except Exception:
+            if messages:
+                import traceback
+                traceback.print_exc()