qt6: Add a Qt 5 warning

Closes #7742

3 files changed, 43 insertions, 0 deletions

diff --git a/qutebrowser/app.py b/qutebrowser/app.py
index bb2ff56e7..fbfa3df12 100644
--- a/qutebrowser/app.py
+++ b/qutebrowser/app.py
@@ -367,6 +367,14 @@ def _open_special_pages(args):
              os.environ.get("QTWEBENGINE_DISABLE_SANDBOX") == "1"
          ),
          'qute://warning/sandboxing'),
+
+        ('qt5-warning-shown',
+         (
+             machinery.IS_QT5 and
+             machinery.INFO.reason == machinery.SelectionReason.auto and
+             objects.backend != usertypes.Backend.QtWebKit,
+         ),
+         'qute://warning/qt5'),
     ]
 
     if 'quickstart-done' not in general_sect:
diff --git a/qutebrowser/browser/qutescheme.py b/qutebrowser/browser/qutescheme.py
index 25834670b..0073f9bd2 100644
--- a/qutebrowser/browser/qutescheme.py
+++ b/qutebrowser/browser/qutescheme.py
@@ -22,6 +22,7 @@ Module attributes:
     _HANDLERS: The handlers registered via decorators.
 """
 
+import sys
 import html
 import json
 import os
@@ -583,6 +584,12 @@ def qute_warning(url: QUrl) -> _HandlerRet:
     elif path == '/sandboxing':
         src = jinja.render('warning-sandboxing.html',
                            title='Qt 6 macOS sandboxing warning')
+    elif path == '/qt5':
+        is_venv = hasattr(sys, 'real_prefix') or sys.base_prefix != sys.prefix
+        src = jinja.render('warning-qt5.html',
+                           title='Switch to Qt 6',
+                           is_venv=is_venv,
+                           prefix=sys.prefix)
     else:
         raise NotFoundError("Invalid warning page {}".format(path))
     return 'text/html', src
diff --git a/qutebrowser/html/warning-qt5.html b/qutebrowser/html/warning-qt5.html
new file mode 100644
index 000000000..17af2f72c
--- /dev/null
+++ b/qutebrowser/html/warning-qt5.html
@@ -0,0 +1,28 @@
+{% extends "styled.html" %}
+
+{% block content %}
+<h1>{{ title }}</h1>
+<span class="note">Note this warning will only appear once. Use <span class="mono">:open
+qute://warning/qt5</span> to show it again at a later time.</span>
+
+<p>
+    qutebrowser <b>now supports Qt 6</b>.
+</p>
+<p>
+    However, in your environment, <b>Qt 6 is not installed</b>. Thus, qutebrowser is still using Qt 5 instead.
+
+    Qt 5.15 based on a very old Chromium version (83 or 87, from mid/late 2020).
+</p>
+{% if is_venv %}
+<p>
+    You are using a virtualenv. If you want to use Qt 6, you need to create a new
+    virtualenv with PyQt6 installed.
+
+    If using <span class="mono">mkvenv.py</span>, <b>rerun the script</b> to create a
+    new virtualenv with Qt 6.
+</p>
+{% endif %}
+<p>
+    <span class="note">Python installation prefix: <span class="mono">{{ prefix }}</span></span>
+</p>
+{% endblock %}