Adding upstream version 3.0.43.upstream/3.0.43

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 41 insertions, 0 deletions

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+.. _input_hooks:
+
+
+Input hooks
+===========
+
+Input hooks are a tool for inserting an external event loop into the
+prompt_toolkit event loop, so that the other loop can run as long as
+prompt_toolkit (actually asyncio) is idle. This is used in applications like
+`IPython <https://ipython.org/>`_, so that GUI toolkits can display their
+windows while we wait at the prompt for user input.
+
+As a consequence, we will "trampoline" back and forth between two event loops.
+
+.. note::
+
+    This will use a :class:`~asyncio.SelectorEventLoop`, not the :class:
+    :class:`~asyncio.ProactorEventLoop` (on Windows) due to the way the
+    implementation works (contributions are welcome to make that work).
+
+
+.. code:: python
+
+    from prompt_toolkit.eventloop.inputhook import set_eventloop_with_inputhook
+
+    def inputhook(inputhook_context):
+        # At this point, we run the other loop. This loop is supposed to run
+        # until either `inputhook_context.fileno` becomes ready for reading or
+        # `inputhook_context.input_is_ready()` returns True.
+
+        # A good way is to register this file descriptor in this other event
+        # loop with a callback that stops this loop when this FD becomes ready.
+        # There is no need to actually read anything from the FD.
+
+        while True:
+            ...
+
+    set_eventloop_with_inputhook(inputhook)
+
+    # Any asyncio code at this point will now use this new loop, with input
+    # hook installed.