Support disabling a lifecycle state by setting a delay of -1

This is inspired by previous iterations of this feature. Discarding a
page can lose information on the page, for example, if you go to
duckduckgo.com and put some text in the search box, then switch to a
different tab and wait for the ddg tab to be discarded, when you switch
back to the ddg tab the search box will be empty.

Until a point where we have more sophisticated controls of what sites
these transitions apply to, it may be useful for users to disable the
discard state completely. I know that's how I've had the lazier loading
implementation set up for years.

Negative numbers would previously have raised a warning on every state
transition where the time complained that negative numbers weren't
supported.

qutebrowser/browser/webengine/webenginetab.py

@@ -1761,6 +1761,9 @@ class WebEngineTab(browsertab.AbstractTab):
         if self._widget.page().lifecycleState() == recommended_state:
             return
 
+        if delay < 0:
+            return
+
         log.webview.debug(f"Scheduling recommended lifecycle change {delay=} {recommended_state=} tab={self}")
         self._lifecycle_timer.timeout.connect(lambda: self._set_lifecycle_state(recommended_state))
         self._lifecycle_timer.start(delay)

qutebrowser/config/configdata.yml

@@ -349,6 +349,7 @@ qt.chromium.use_recommended_page_lifecycle_state:
   type: Bool
   default: false
   backend: QtWebEngine
+  # yamllint disable rule:line-length
   desc: >-
     Use recommended page lifecycle state.
 
@@ -361,6 +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.
 
+    See the Qt documentation for more details: https://doc.qt.io/qt-6/qtwebengine-features.html#page-lifecycle-api
+  # yamllint enable rule:line-length
+
 qt.chromium.lifecycle_state_freeze_delay:
   type: Int
   default: 0
@@ -369,6 +373,8 @@ qt.chromium.lifecycle_state_freeze_delay:
     The amount of time (in milliseconds) to wait before transitioning a page to
     the frozen lifecycle state.
 
+    Set to -1 to disable this state (will also disable the discard state).
+
 qt.chromium.lifecycle_state_discard_delay:
   type: Int
   default: 0
@@ -377,6 +383,8 @@ qt.chromium.lifecycle_state_discard_delay:
     The amount of time (in milliseconds) to wait before transitioning a page to
     the discarded lifecycle state.
 
+    Set to -1 to disable this state.
+
 qt.highdpi:
   type: Bool
   default: false

tests/unit/browser/webengine/test_webenginetab.py

@@ -333,6 +333,20 @@ class TestPageLifecycle:
             pass
         set_state_spy.assert_called_once_with(new_state)
 
+    def test_state_disabled(
+        self,
+        webengine_tab: webenginetab.WebEngineTab,
+        monkeypatch,
+        config_stub,
+    ):
+        """For negative delay values, the timer shouldn't be scheduled."""
+        self.set_config(
+            config_stub,
+            freeze_delay=-1,
+        )
+        webengine_tab._on_recommended_state_changed(QWebEnginePage.LifecycleState.Frozen)
+        assert not webengine_tab._lifecycle_timer.isActive()
+
     def test_timer_interrupted(
         self,
         webengine_tab: webenginetab.WebEngineTab,