Ignore mouse events going to non-main widgets

When we hide the context menu on QtWebEngine, we get a mouse event
relative to the QMenu in the filter, which means tab.elements.at_pos
will get called with a negative position (and thus assert) or at least a
wrong position.

qutebrowser/browser/browsertab.py

@@ -470,6 +470,10 @@ class AbstractTab(QWidget):
 
     We use this to unify QWebView and QWebEngineView.
 
+    Class attributes:
+        WIDGET_CLASS: The class of the main widget recieving events.
+                      Needs to be overridden by subclasses.
+
     Attributes:
         history: The AbstractHistory for the current tab.
         registry: The ObjectRegistry associated with this tab.
@@ -503,6 +507,8 @@ class AbstractTab(QWidget):
     contents_size_changed = pyqtSignal(QSizeF)
     add_history_item = pyqtSignal(QUrl, QUrl, str)  # url, requested url, title
 
+    WIDGET_CLASS = None
+
     def __init__(self, win_id, parent=None):
         self.win_id = win_id
         self.tab_id = next(tab_id_gen)
@@ -529,7 +535,8 @@ class AbstractTab(QWidget):
         self._progress = 0
         self._has_ssl_errors = False
         self._load_status = usertypes.LoadStatus.none
-        self._mouse_event_filter = mouse.MouseEventFilter(self, parent=self)
+        self._mouse_event_filter = mouse.MouseEventFilter(
+            self, widget_class=self.WIDGET_CLASS, parent=self)
         self.backend = None
 
         # FIXME:qtwebengine  Should this be public api via self.hints?

qutebrowser/browser/mouse.py

@@ -64,6 +64,8 @@ class MouseEventFilter(QObject):
     """Handle mouse events on a tab.
 
     Attributes:
+        _widget_class: The class of the main widget getting the events.
+                       All other events are ignored.
         _tab: The browsertab object this filter is installed on.
         _handlers: A dict of handler functions for the handled events.
         _ignore_wheel_event: Whether to ignore the next wheelEvent.
@@ -71,8 +73,9 @@ class MouseEventFilter(QObject):
                                       done when the mouse is released.
     """
 
-    def __init__(self, tab, parent=None):
+    def __init__(self, tab, *, widget_class, parent=None):
         super().__init__(parent)
+        self._widget_class = widget_class
         self._tab = tab
         self._handlers = {
             QEvent.MouseButtonPress: self._handle_mouse_press,
@@ -219,9 +222,14 @@ class MouseEventFilter(QObject):
             self._tab.data.open_target = usertypes.ClickTarget.normal
             log.mouse.debug("Normal click, setting normal target")
 
-    def eventFilter(self, _obj, event):
+    def eventFilter(self, obj, event):
         """Filter events going to a QWeb(Engine)View."""
         evtype = event.type()
         if evtype not in self._handlers:
             return False
+        if not isinstance(obj, self._widget_class):
+            log.mouse.debug("Ignoring {} to {} which is not an instance of "
+                            "{}".format(event.__class__.__name__, obj,
+                                        self._widget_class))
+            return False
         return self._handlers[evtype](event)

qutebrowser/browser/webengine/webenginetab.py

@@ -27,6 +27,7 @@ import functools
 from PyQt5.QtCore import pyqtSlot, Qt, QEvent, QPoint, QUrl
 from PyQt5.QtGui import QKeyEvent, QIcon
 # pylint: disable=no-name-in-module,import-error,useless-suppression
+from PyQt5.QtWidgets import QOpenGLWidget
 from PyQt5.QtWebEngineWidgets import QWebEnginePage, QWebEngineScript
 # pylint: enable=no-name-in-module,import-error,useless-suppression
 
@@ -376,6 +377,8 @@ class WebEngineTab(browsertab.AbstractTab):
 
     """A QtWebEngine tab in the browser."""
 
+    WIDGET_CLASS = QOpenGLWidget
+
     def __init__(self, win_id, mode_manager, parent=None):
         super().__init__(win_id)
         widget = webview.WebEngineView(tabdata=self.data)

qutebrowser/browser/webkit/webkittab.py

@@ -574,6 +574,8 @@ class WebKitTab(browsertab.AbstractTab):
 
     """A QtWebKit tab in the browser."""
 
+    WIDGET_CLASS = webview.WebView
+
     def __init__(self, win_id, mode_manager, parent=None):
         super().__init__(win_id)
         widget = webview.WebView(win_id, self.tab_id, tab=self)