Ignore tab key presses if they'd switch focus.

If the mainwindow is focused but not the web view (e.g. in prompt mode), an
unbound tab key should be filtered so it doesn't change keyboard focus.

Fixes #504.

qutebrowser/keyinput/modeman.py

@@ -26,8 +26,9 @@
 import functools
 
 from PyQt5.QtGui import QWindow
-from PyQt5.QtCore import pyqtSignal, QObject, QEvent
+from PyQt5.QtCore import pyqtSignal, Qt, QObject, QEvent
 from PyQt5.QtWidgets import QApplication
+from PyQt5.QtWebKitWidgets import QWebView
 
 from qutebrowser.keyinput import modeparsers, keyparser
 from qutebrowser.config import config
@@ -181,9 +182,13 @@ def _eventFilter_keypress(self, event):
         handled = handler(event) if handler is not None else False
 
         is_non_alnum = bool(event.modifiers()) or not event.text().strip()
+        focus_widget = QApplication.instance().focusWidget()
+        is_tab = event.key() in (Qt.Key_Tab, Qt.Key_Backtab)
 
         if handled:
             filter_this = True
+        elif is_tab and not isinstance(focus_widget, QWebView):
+            filter_this = True
         elif (curmode in self.passthrough or
                 self._forward_unbound_keys == 'all' or
                 (self._forward_unbound_keys == 'auto' and is_non_alnum)):
@@ -196,12 +201,11 @@ def _eventFilter_keypress(self, event):
 
         if curmode != usertypes.KeyMode.insert:
             log.modes.debug("handled: {}, forward-unbound-keys: {}, "
-                            "passthrough: {}, is_non_alnum: {} --> filter: "
-                            "{} (focused: {!r})".format(
+                            "passthrough: {}, is_non_alnum: {}, is_tab {} --> "
+                            "filter: {} (focused: {!r})".format(
                                 handled, self._forward_unbound_keys,
-                                curmode in self.passthrough,
-                                is_non_alnum, filter_this,
-                                QApplication.instance().focusWidget()))
+                                curmode in self.passthrough, is_non_alnum,
+                                is_tab, filter_this, focus_widget))
         return filter_this
 
     def _eventFilter_keyrelease(self, event):