Use QApplication.sendEvent instead of postEvent

From the QApplication.postEvent docs:
http://doc.qt.io/qt-5/qcoreapplication.html#postEvent

  The event must be allocated on the heap since the post event queue
  will take ownership of the event and delete it once it has been
  posted. It is not safe to access the event after it has been posted.

We can't reliably guarantee that from Python, so we need to use
sendEvent instead.

qutebrowser/browser/browsertab.py

@@ -562,7 +562,7 @@ class AbstractTab(QWidget):
         self._load_status = val
         self.load_status_changed.emit(val.name)
 
-    def post_event(self, evt):
+    def send_event(self, evt):
         """Send the given event to the underlying widget."""
         raise NotImplementedError
 

qutebrowser/browser/commands.py

@@ -1953,8 +1953,8 @@ class CommandDispatcher:
                 window = QApplication.focusWindow()
                 if window is None:
                     raise cmdexc.CommandError("No focused window!")
-                QApplication.postEvent(window, press_event)
-                QApplication.postEvent(window, release_event)
+                QApplication.sendEvent(window, press_event)
+                QApplication.sendEvent(window, release_event)
             else:
                 try:
                     tab = objreg.get('tab', scope='tab', tab='current')
@@ -1962,8 +1962,8 @@ class CommandDispatcher:
                     raise cmdexc.CommandError("No focused webview!")
 
                 tab = self._current_widget()
-                tab.post_event(press_event)
-                tab.post_event(release_event)
+                tab.send_event(press_event)
+                tab.send_event(release_event)
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        debug=True)

qutebrowser/browser/webelem.py

@@ -384,7 +384,7 @@ class AbstractWebElement(collections.abc.MutableMapping):
         ]
 
         for evt in events:
-            self._tab.post_event(evt)
+            self._tab.send_event(evt)
 
         def after_click():
             """Move cursor to end and reset override_target after clicking."""
@@ -398,4 +398,4 @@ class AbstractWebElement(collections.abc.MutableMapping):
         pos = self._mouse_pos()
         event = QMouseEvent(QEvent.MouseMove, pos, Qt.NoButton, Qt.NoButton,
                             Qt.NoModifier)
-        self._tab.post_event(event)
+        self._tab.send_event(event)

qutebrowser/browser/webengine/webenginetab.py

@@ -201,8 +201,8 @@ class WebEngineScroller(browsertab.AbstractScroller):
         press_evt = QKeyEvent(QEvent.KeyPress, key, Qt.NoModifier, 0, 0, 0)
         release_evt = QKeyEvent(QEvent.KeyRelease, key, Qt.NoModifier, 0, 0, 0)
         for _ in range(count):
-            self._tab.post_event(press_evt)
-            self._tab.post_event(release_evt)
+            self._tab.send_event(press_evt)
+            self._tab.send_event(release_evt)
 
     @pyqtSlot()
     def _update_pos(self):
@@ -523,8 +523,6 @@ class WebEngineTab(browsertab.AbstractTab):
         except AttributeError:
             log.stub('contentsSizeChanged, on Qt < 5.7')
 
-    def post_event(self, evt):
-        # If we get a segfault here, we might want to try sendEvent
-        # instead.
+    def send_event(self, evt):
         recipient = self._widget.focusProxy()
-        QApplication.postEvent(recipient, evt)
+        QApplication.sendEvent(recipient, evt)

qutebrowser/browser/webkit/webkittab.py

@@ -696,7 +696,5 @@ class WebKitTab(browsertab.AbstractTab):
         frame.initialLayoutCompleted.connect(self._on_history_trigger)
         page.link_clicked.connect(self._on_link_clicked)
 
-    def post_event(self, evt):
-        # If we get a segfault here, we might want to try sendEvent
-        # instead.
-        QApplication.postEvent(self._widget, evt)
+    def send_event(self, evt):
+        QApplication.sendEvent(self._widget, evt)

tests/end2end/features/scroll.feature

@@ -72,6 +72,11 @@ Feature: Scrolling
         And I run :scroll left
         Then the page should not be scrolled
 
+    # causes segfault with postEvent instead of sendEvent
+    Scenario: Scrolling down with count 10
+        When I run :scroll down with count 10
+        Then no crash should happen
+
     Scenario: Scrolling with page down
         When I run :scroll page-down
         Then the page should be scrolled vertically

tests/unit/utils/test_debug.py

@@ -39,7 +39,7 @@ class EventObject(QObject):
 
 def test_log_events(qapp, caplog):
     obj = EventObject()
-    qapp.postEvent(obj, QEvent(QEvent.User))
+    qapp.sendEvent(obj, QEvent(QEvent.User))
     qapp.processEvents()
     assert len(caplog.records) == 1
     assert caplog.records[0].msg == 'Event in test_debug.EventObject: User'