Extend Qt event relaying

Add an `open_handler()` ctx manager for wholesale handling event sets
with a passed in async func. Better document and implement the event
filtering core including adding support for key "auto repeat" filtering;
it turns out the events delivered when `trio` does its guest-most tick
are not the same (Qt has somehow consumed them or something) so we have
to do certain things (like getting the `.type()`, `.isAutoRepeat()`,
etc.) before shipping over the mem chan. The alt might be to copy the
event objects first but haven't tried it yet. For now just offer
auto-repeat filtering through a flag.

piker/ui/_event.py

@@ -19,27 +19,41 @@ Qt event proxying and processing using ``trio`` mem chans.
 
 """
 from contextlib import asynccontextmanager
+from typing import Callable
 
-from PyQt5 import QtCore, QtGui
+from PyQt5 import QtCore
 from PyQt5.QtCore import QEvent
+from PyQt5.QtGui import QWidget
 import trio
 
 
-class EventCloner(QtCore.QObject):
-    """Clone and forward keyboard events over a trio memory channel
-    for later async processing.
+class EventRelay(QtCore.QObject):
+    '''
+    Relay Qt events over a trio memory channel for async processing.
 
-    """
+    '''
     _event_types: set[QEvent] = set()
     _send_chan: trio.abc.SendChannel = None
+    _filter_auto_repeats: bool = True
 
     def eventFilter(
         self,
-        source: QtGui.QWidget,
+        source: QWidget,
         ev: QEvent,
     ) -> None:
+        '''
+        Qt global event filter: return `False` to pass through and `True`
+        to filter event out.
 
-        if ev.type() in self._event_types:
+        https://doc.qt.io/qt-5/qobject.html#eventFilter
+        https://doc.qt.io/qtforpython/overviews/eventsandfilters.html#event-filters
+
+        '''
+        etype = ev.type()
+        # print(f'etype: {etype}')
+
+        if etype in self._event_types:
+            # ev.accept()
 
             # TODO: what's the right way to allow this?
             # if ev.isAutoRepeat():
@@ -51,35 +65,54 @@ class EventCloner(QtCore.QObject):
             # something to do with Qt internals and calling the
             # parent handler?
 
+            if etype in {QEvent.KeyPress, QEvent.KeyRelease}:
+
+                # TODO: is there a global setting for this?
+                if ev.isAutoRepeat() and self._filter_auto_repeats:
+                    ev.ignore()
+                    return True
+
                 key = ev.key()
                 mods = ev.modifiers()
                 txt = ev.text()
 
-            # run async processing
-            self._send_chan.send_nowait((ev, key, mods, txt))
+                # NOTE: the event object instance coming out
+                # the other side is mutated since Qt resumes event
+                # processing **before** running a ``trio`` guest mode
+                # tick, thus special handling or copying must be done.
 
-        # never intercept the event
+                # send elements to async handler
+                self._send_chan.send_nowait((ev, etype, key, mods, txt))
+
+            else:
+                # send event to async handler
+                self._send_chan.send_nowait(ev)
+
+            # **do not** filter out this event
+            # and instead forward to the source widget
+            return False
+
+        # filter out this event
+        # https://doc.qt.io/qt-5/qobject.html#installEventFilter
         return False
 
 
 @asynccontextmanager
-async def open_key_stream(
+async def open_event_stream(
 
-    source_widget: QtGui.QWidget,
+    source_widget: QWidget,
     event_types: set[QEvent] = {QEvent.KeyPress},
-
-    # TODO: should we offer some kinda option for toggling releases?
-    # would it require a channel per event type?
-    # QEvent.KeyRelease,
+    filter_auto_repeats: bool = True,
 
 ) -> trio.abc.ReceiveChannel:
 
     # 1 to force eager sending
     send, recv = trio.open_memory_channel(16)
 
-    kc = EventCloner()
+    kc = EventRelay()
     kc._send_chan = send
     kc._event_types = event_types
+    kc._filter_auto_repeats = filter_auto_repeats
 
     source_widget.installEventFilter(kc)
 
@@ -89,3 +122,22 @@ async def open_key_stream(
     finally:
         await send.aclose()
         source_widget.removeEventFilter(kc)
+
+
+@asynccontextmanager
+async def open_handler(
+
+    source_widget: QWidget,
+    event_types: set[QEvent],
+    async_handler: Callable[[QWidget, trio.abc.ReceiveChannel], None],
+    **kwargs,
+
+) -> None:
+
+    async with (
+        trio.open_nursery() as n,
+        open_event_stream(source_widget, event_types, **kwargs) as event_recv_stream,
+    ):
+        n.start_soon(async_handler, source_widget, event_recv_stream)
+        yield
+        n.cancel_scope.cancel()