##// END OF EJS Templates
Backport PR #2294: inputhook_qt4: Use QEventLoop instead of starting up the QCoreApplication...
Backport PR #2294: inputhook_qt4: Use QEventLoop instead of starting up the QCoreApplication I referenced this branch in #2080 and was letting it sit for a little while, but I have decided to make it a full pull request to get some additional visibility. Essentially our Qt event loop mechanism repeatedly starts and quits a `QCoreApplication` object. Unfortunately the `QCoreApplication::quit` slot has a lot of unintended side effects (like emitting an `aboutToQuit` signal which closes all open file dialogs). For our input hook, we _might_ be able to get by with just using a `QEventLoop` whose quit slot is much simpler and less destructive. For a little bit of background on why one might want to just use `QEventLoop::exec`, let's examine what `QCoreApplication::exec` does: ```c++ int QCoreApplication::exec() { if (!QCoreApplicationPrivate::checkInstance("exec")) return -1; // ... [some assertions] threadData->quitNow = false; QEventLoop eventLoop; self->d_func()->in_exec = true; self->d_func()->aboutToQuitEmitted = false; int returnCode = eventLoop.exec(); threadData->quitNow = false; if (self) { self->d_func()->in_exec = false; if (!self->d_func()->aboutToQuitEmitted) emit self->aboutToQuit(); self->d_func()->aboutToQuitEmitted = true; sendPostedEvents(0, QEvent::DeferredDelete); } return returnCode; } ``` As far as I can tell, it's a small wrapper around `QEventLoop::exec` which also: * Sets some variables regarding the current status * Emits an `aboutToQuit` signal right before the function returns (which is the root cause of @denisri's problem in #2080). Historically, our Qt event loop is a python implementation of the (win 32) input hook supplied with the PyQt4 source (see qtcore_input_hook` in `python-qt4/sip/QtCore/qcoreapplication.sip`), which more or less dates to a [mailing list post](http://www.riverbankcomputing.com/pipermail/pyqt/2007-July/016512.html) from July 2007.

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completion_plain.py
62 lines | 2.3 KiB | text/x-python | PythonLexer
"""a simple completer for the qtconsole"""
#-----------------------------------------------------------------------------
# Copyright (c) 2012, IPython Development Team.$
#
# Distributed under the terms of the Modified BSD License.$
#
# The full license is in the file COPYING.txt, distributed with this software.
#-------------------------------------------------------------------
# System library imports
from IPython.external.qt import QtCore, QtGui
import IPython.utils.text as text
class CompletionPlain(QtGui.QWidget):
""" A widget for tab completion, navigable by arrow keys """
#--------------------------------------------------------------------------
# 'QObject' interface
#--------------------------------------------------------------------------
def __init__(self, console_widget):
""" Create a completion widget that is attached to the specified Qt
text edit widget.
"""
assert isinstance(console_widget._control, (QtGui.QTextEdit, QtGui.QPlainTextEdit))
super(CompletionPlain, self).__init__()
self._text_edit = console_widget._control
self._console_widget = console_widget
self._text_edit.installEventFilter(self)
def eventFilter(self, obj, event):
""" Reimplemented to handle keyboard input and to auto-hide when the
text edit loses focus.
"""
if obj == self._text_edit:
etype = event.type()
if etype in( QtCore.QEvent.KeyPress, QtCore.QEvent.FocusOut ):
self.cancel_completion()
return super(CompletionPlain, self).eventFilter(obj, event)
#--------------------------------------------------------------------------
# 'CompletionPlain' interface
#--------------------------------------------------------------------------
def cancel_completion(self):
"""Cancel the completion, reseting internal variable, clearing buffer """
self._console_widget._clear_temporary_buffer()
def show_items(self, cursor, items):
""" Shows the completion widget with 'items' at the position specified
by 'cursor'.
"""
if not items :
return
self.cancel_completion()
strng = text.columnize(items)
self._console_widget._fill_temporary_buffer(cursor, strng, html=False)