Restrict page lifecycle feature to Qt6.5+

There is some weirdness preventing us from connecting to the
`QWebEnginePage.recommendedStateChanged` on WebEngine 6.4 and below. We
get this message from QT:

    qt.core.qobject.connect: QObject::connect: No such signal WebEnginePage::recommendedStateChanged(QWebEnginePage::LifecycleState)

and this message from PyQt:

    TypeError: connect() failed between recommendedStateChanged(QWebEnginePage::LifecycleState) and _on_recommended_state_changed()

We couldn't get to the root of it, but we shouldn't have a pressing need
to support this on older versions anyway since later Qt versions are
already widespread.

qutebrowser/browser/webengine/webenginetab.py

@@ -1791,7 +1791,8 @@ class WebEngineTab(browsertab.AbstractTab):
         page.printRequested.connect(self._on_print_requested)
         page.selectClientCertificate.connect(self._on_select_client_certificate)
 
-        page.recommendedStateChanged.connect(self._on_recommended_state_changed)
+        if version.qtwebengine_versions().webengine >= utils.VersionNumber(6, 5):
+            page.recommendedStateChanged.connect(self._on_recommended_state_changed)
 
         view.titleChanged.connect(self.title_changed)
         view.urlChanged.connect(self._on_url_changed)

qutebrowser/config/configdata.yml

@@ -362,6 +362,9 @@ qt.chromium.use_recommended_page_lifecycle_state:
     Ongoing page activity is taken into account when determining the
     recommended lifecycle state, as to not disrupt your browsing.
 
+    This feature is only available on QtWebEngine 6.5+. On older versions
+    this setting is ignored.
+
     See the Qt documentation for more details: https://doc.qt.io/qt-6/qtwebengine-features.html#page-lifecycle-api
   # yamllint enable rule:line-length
 

tests/end2end/features/tabs.feature

@@ -1990,6 +1990,7 @@ Feature: Tab management
         And I run :tab-prev
         Then "Entering mode KeyMode.insert (reason: mode_override)" should be logged
 
+    @qt>=6.5
     Scenario: Lifecycle change on tab switch
         When I set qt.chromium.use_recommended_page_lifecycle_state to true
         And I open about:blank?1

tests/unit/browser/webengine/test_webenginetab.py

@@ -14,12 +14,14 @@ QWebEngineScriptCollection = QtWebEngineCore.QWebEngineScriptCollection
 QWebEngineScript = QtWebEngineCore.QWebEngineScript
 
 from qutebrowser.browser import greasemonkey
-from qutebrowser.utils import usertypes
+from qutebrowser.utils import usertypes, utils, version
 webenginetab = pytest.importorskip(
     "qutebrowser.browser.webengine.webenginetab")
 
 pytestmark = pytest.mark.usefixtures('greasemonkey_manager')
 
+versions = version.qtwebengine_versions(avoid_init=True)
+
 
 class ScriptsHelper:
 
@@ -248,6 +250,14 @@ class TestWebEnginePermissions:
 
 class TestPageLifecycle:
 
+    @pytest.fixture(autouse=True)
+    def check_version(self):
+        # While the lifecycle feature was introduced in 5.14, PyQt seems to
+        # have trouble connecting to the signal we require on 6.4 and prior.
+        # https://github.com/qutebrowser/qutebrowser/pull/8547#issuecomment-2890997662
+        if versions.webengine < utils.VersionNumber(6, 5):
+            pytest.skip("Lifecycle feature requires Webengine 6.5+")
+
     @pytest.fixture
     def set_state_spy(
         self,