I want the output of a function that runs in a thread to be shown in a
QPlainTextEdit on the main window. Now this crashes with a message that
I sould use qRegisterMetaType. There are dozens of entries on the web on
this but I could not find any that tells how to. At least not how to in
python.
My handicap is that I have not too much experience with oo-programming
and none at all with c++. Thus suggestions like "call
qRegisterMetaType() to register the data type before you establish the
connection." are of no help and I have no idea what to make of things
like "qRegisterMetaType<VolumeType>( "VolumeType" );"
Please can someone tell me what to do with the small example below to
get it working.
#!/usr/bin/python
"""
Small test application for threaded output to a QPlainTextEdit.
The main window consists of three buttons and the QPlainTextEdit
- pressButtonInsert clicked is connected to slotInsert: append text to
the edit widget
- pressButtonThread clicked is connected to slotInsertThreaded:
append text to edit widget from within a separate thread
- pressButtonClear clicked is connected to slotClear: clear the edit widget
"""
import sys, time
from PyQt4 import QtCore, QtGui
from qPlainTextEditGui import Ui_Form #the main form containing the 4
widgets
class MyForm(QtGui.QMainWindow):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self, parent)
self.ui = Ui_Form()
self.ui.setupUi(self)
def slotClear(self):
print('ButtonClear triggered')
self.ui.plainTextEdit.clear()
def slotInsert(self):
print('ButtonInsert triggered')
append_to_edit(self.ui.plainTextEdit)
def slotInsertThreaded(self):
print('ButtonTreaded triggered')
self.work = work_thread(self.ui.plainTextEdit)
self.work.start()
class work_thread(QtCore.QThread):
"""
After http://joplaete.wordpress.com/2010/07/21/threading-with-pyqt4/
"""
def __init__(self, edit, parent=None):
QtCore.QThread.__init__(self, parent)
self.edit = edit
def run(self):
append_to_edit(self.edit)
def append_to_edit(edit):
for i in range(5):
edit.appendPlainText('line %d' % i)
time.sleep(0.5)
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
myapp = MyForm()
myapp.show()
sys.exit(app.exec_())
Now it works fine when pressButtonInsert is triggered but returns this
when pressButtonThread is triggered:
QObject::connect: Cannot queue arguments of type 'QTextBlock'
(Make sure 'QTextBlock' is registered using qRegisterMetaType().)
QObject::connect: Cannot queue arguments of type 'QTextCursor'
(Make sure 'QTextCursor' is registered using qRegisterMetaType().)
Many thanks for helping me out,
Janwillem
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