Micro-optimize global eventFilter

Might not make a big difference, but probably worth it, given that this can be
called a lot when there are events coming to Qt.

Based on a couple of assumptions:

- We won't be interested in most events
- Very often, events are not going to a QWindow, so we discard them as early as
  possible.
- Very often, it's an event of a type we're not interested in, so we also
  discard those as early as possible.
- "not self._activated" happens rarely.
- "if typ not in self._handlers:" is significantly faster than try/except
  KeyError
- try:/except: is only needed around the handler call itself, as we can be
  reasonably certain the code above won't raise an exception.

See #5376

1 files changed, 15 insertions, 12 deletions

diff --git a/qutebrowser/keyinput/eventfilter.py b/qutebrowser/keyinput/eventfilter.py
index 7916f16fe..992d9f4ce 100644
--- a/qutebrowser/keyinput/eventfilter.py
+++ b/qutebrowser/keyinput/eventfilter.py
@@ -85,19 +85,22 @@ class EventFilter(QObject):
         Return:
             True if the event should be filtered, False if it's passed through.
         """
+        if not isinstance(obj, QWindow):
+            # We already handled this same event at some point earlier, so
+            # we're not interested in it anymore.
+            return False
+
+        typ = event.type()
+
+        if typ not in self._handlers:
+            return False
+
+        if not self._activated:
+            return False
+
+        handler = self._handlers[typ]
         try:
-            if not self._activated:
-                return False
-            if not isinstance(obj, QWindow):
-                # We already handled this same event at some point earlier, so
-                # we're not interested in it anymore.
-                return False
-            try:
-                handler = self._handlers[event.type()]
-            except KeyError:
-                return False
-            else:
-                return handler(event)
+            return handler(event)
         except:
             # If there is an exception in here and we leave the eventfilter
             # activated, we'll get an infinite loop and a stack overflow.