2008-08-09T16:24:36Z

Axiom: /* KDE4 Issues */

==KDE4 Issues==
*<s>No admin button in system settings</s>
**''They know about this [[Schedules/KDE4/4.2_Release_Schedule]]
**do <tt>sudo /usr/lib/kde4/bin/systemsettings</tt>
*'''GTK-QT not working, Firefox looks awful'''
**installed gtk-qt-engine-kde4 and it appears in system settings, but has no effect on firefox, thunderbird, gimp, etc.
**[http://ubuntuforums.org/showthread.php?t=864426&highlight=kde4 Other have this problem] ''no solutions''
*Firefox cannot properly set helper applications (ktorrent, okular, etc)
*Cannot set khotkeys for media keys on logitech keyboard
**khotkeys is "in a bit of a broken state" ''no known workarounds''
*<s>Dolphin has no "Open Terminal here" option</s> ''an icon can be added to the toolbar''
*Ark does not seem to handle tar.bz2 files (extracts an empty directory)
*Amarok crashes every time I run it (need to compile amarok 2.0)
*Mixer control have no effect on volume
**Used to have a little volume bar in my kicker that I could control with my mouse wheel. WANT.
*Sound works right only some of the time. Startup sound starts playing fine, and then gets cutoff
**Phonon sometimes gives weird sound failing message
*Surround sound does not work at all. Conflicting instructions on how to set this up, but no settings in KDE4 anywhere that I can see
*Kaffeine and Amarok appear to be stealing Xine from each other
**(Kaffeine is working on a KDE4 release coming ''soon''. Dragon player doesn't work/has no settings)
*<s>Flash randomly stops working in Firefox. It will start out fine, and then after a bit will only show grey boxes where flash should be. 64bit thing? Why would it do this?</s> ''It seems this is a problem only with the official ubuntu firefox package. The mozilla package works fine''
*Dolphin has no right-click extract options ''ark can't handle this?''
*KDE tries to start applications I had running on logout every time I logout. I '''do not''' want it to do this!

==Wishlist==
*Hide cursor when zoomed in

User:Axiom/KDE4

2008-08-09T03:03:03Z

Axiom: /* Wishlist */

User:Axiom/KDE4

2008-08-09T02:46:57Z

Axiom: /* KDE4 Issues */

User:Axiom/KDE4

2008-08-09T02:45:08Z

Axiom:

User:Axiom/KDE4

2008-08-09T02:04:01Z

Axiom:

==KDE4 Issues==
*Is there a way to safely turn off desktop effects if they are causing crashing? Like safemode? Or some sort of config file?
*Can't add proper shortcuts to non-kde applications in menus or quick launch
*<s>No admin button in system settings</s>
**''They know about this [[Schedules/KDE4/4.2_Release_Schedule]]
**do <tt>sudo /usr/lib/kde4/bin/systemsettings</tt>
*GTK-QT not working, Firefox looks awful
*Firefox cannot properly set helper applications (ktorrent, okular, etc)
*Cannot set khotkeys for media keys on logitech keyboard
*<s>Dolphin has no "Open Terminal here" option</s> ''an icon can be added to the toolbar''
*Ark does not seem to handle tar.bz2 files (extracts an empty directory)
*Amarok crashes every time I run it (need to compile amarok 2.0)
*Mixer control have no effect on volume
**Used to have a little volume bar in my kicker that I could control with my mouse wheel. WANT.
*Sound works right only some of the time. Startup sound starts playing fine, and then gets cutoff
**Phonon sometimes gives weird sound failing message
*Surround sound does not work at all. Conflicting instructions on how to set this up, but no settings in KDE4 anywhere that I can see
*Kaffeine and Amarok appear to be stealing Xine from each other
**(Kaffeine is working on a KDE4 release coming ''soon''. Dragon player doesn't work/has no settings)
*<s>Flash randomly stops working in Firefox. It will start out fine, and then after a bit will only show grey boxes where flash should be. 64bit thing? Why would it do this?</s> ''It seems this is a problem only with the official ubuntu firefox package. The mozilla package works fine''
*Dolphin has no right-click extract options ''ark can't handle this?''
*khotkeys is "in a bit of a broken state" ''no known workarounds''
*gtk-qt-engine-kde4 does not work at all ''installed and appears in system settings, but has no effect on firefox, thunderbird, gimp, etc.''
==Wishlist==
*Hide cursor when zoomed int

User:Axiom/KDE4

2008-08-09T01:12:47Z

Axiom: /* KDE4 Issues */

User:Axiom/KDE4

2008-08-08T23:30:37Z

Axiom: /* KDE4 Issues */

2008-08-04T23:37:57Z

Axiom: /* KDE4 Issues */

User:Axiom/KDE4

2008-08-04T23:37:27Z

Axiom:

==KDE4 Issues==
*Kicker clock should be 12hr (am/pm) not 24hr
*Is there a way to safely turn off desktop effects if they are causing crashing? Like safemode? Or some sort of config file?
*Can't add proper shortcuts to non-kde applications in menus or quick launch
*No admin button in system settings
**''They know about this [[Schedules/KDE4/4.2_Release_Schedule]]
**do <tt>sudo /usr/lib/kde4/bin/systemsettings</tt>
*GTK-QT not working, Firefox looks awful
*Firefox cannot properly set helper applications (ktorrent, okular, etc)
*Cannot set khotkeys for media keys on logitech keyboard
*Dolphin has no "Open Terminal here" option
*Ark does not seem to handle tar.bz2 files (extracts an empty directory)
*Amarok crashes every time I run it (need to compile amarok 2.0)
*Mixer control have no effect on volume
**Used to have a little volume bar in my kicker that I could control with my mouse wheel. WANT.
*Sound works right only some of the time. Startup sound starts playing fine, and then gets cutoff
**Phonon sometimes gives weird sound failing message
*Surround sound does not work at all. Conflicting instructions on how to set this up, but no settings in KDE4 anywhere that I can see
*Kaffeine and Amarok appear to be stealing Xine from each other
**(Kaffeine is working on a KDE4 release coming ''soon''. Dragon player doesn't work/has no settings)

User:Axiom/KDE4

2008-08-02T15:35:22Z

User:Axiom

2007-03-28T20:15:50Z

Axiom:

==Axiom's sandbox==

I am just putting some stuff here right now, because you have such nice color coding in your wiki. Maybe I'll turn it into a tutorial if I figure out what I am doing.

==Dynamically Loading a .ui file==
I found this snippet [http://kib2.free.fr/pyqt4/pyqt4.html here] (french).
I don't know if this is the right way to do it, but it seems to work.
===loadui.py===
<code python>
import sys
from PyQt4 import QtGui, uic

app = QtGui.QApplication(sys.argv)
widget = uic.loadUi("demo.ui")
widget.show()

# La boucle principale
app.exec_()
</code>
Of course you will need to make a ui file called demo.ui for this to work.

==Connecting Buttons From Dynamically loaded .ui File==

This code really works.

===callMainWindow.py===
<code python>
import sys
from PyQt4 import QtGui
from PyQt4 import uic
from PyQt4 import QtCore

# the class has to have the same base class as your UI
class DemoImpl(QtGui.QMainWindow):
def __init__(self, *args):
QtGui.QMainWindow.__init__(self, *args)
# just pass self
uic.loadUi("mainWindow.ui", self)
#this line makes sure that we are only looking for a string
#if we want a bool as well we can add @QtCore.pyqtSignature("bool")
@QtCore.pyqtSignature("")
def on_button1_clicked(self):
print "You Clicked the button!"
@QtCore.pyqtSignature("")
def on_button2_clicked(self):
print "You Clicked the button2!"

app = QtGui.QApplication(sys.argv)
widget = DemoImpl()
widget.show()
app.exec_()

</code>

You will need [[User:Axiom/demo.ui|this file]] too.

==Getting user input into a variable==
Once you have it in a variable, you can throw the whole power of python at it.
I have tried to show how to do this in the simplest way possible.
''Note: This code shamelessly stolen from [http://www.apaku.de/linux/xpathevaluator/index.php xpathevaluator]. Lots of good pyqt4 sample code in there. Also might be helpful if you want to evaluate an xpath. But I'm not sure why you would want to do that.

===readinput.py===
<code python>
import sys
#Load the widget
from PyQt4.QtGui import QWidget #This is a widget, not a window, and that makes a difference
from PyQt4.uic import loadUiType #We need this to dynamically load the .ui file we created in qt designer
from PyQt4.QtCore import pyqtSignature, Qt #Not sure what this signature thing is, but apparently it is great for buttons (signals/slots?)
import sys

(form, formbase) = loadUiType('readinput.ui') #this is the .ui file we want to show

class readInputWidget(QWidget, form): #in this class, we load the window, and assign actions to the buttons
def __init__(self, parent=None):
QWidget.__init__(self, parent)
self.setAttribute(Qt.WA_DeleteOnClose) #This doesn't seem to change anything if you delete it, but may be usefull for housekeeping
self.setupUi(self)

@pyqtSignature("on_exitButton_clicked()")
def on_exitButton_clicked(self):
self.close()

@pyqtSignature("on_evalButton_clicked()")
def on_evalButton_clicked(self):
print 'This should echo our text:'
userinput = self.inputBox1.text() #This is the fantastic line of code we were waiting for! Make sure you have an input box by that name, and specify that it is text
print userinput

def main():
from PyQt4.QtGui import QApplication
from PyQt4.QtCore import Qt
app = QApplication(sys.argv)
widget = readInputWidget()
widget.show()
return app.exec_()

if __name__ == "__main__":
sys.exit(main())
</code>
You will also need the [[User:Axiom/readinput.ui|ui file]] that goes along with that.

==Writing input to a file, and bringing it back==
This snippet does the same as above, except it saves whatever you type as config.txt, and the next time you run it, it loads the text back into the input field. I got this code from [http://www.daniweb.com/code/snippet389.html here], and [http://www.devshed.com/c/a/Python/PyQT-Input-Widgets/ here].

===readinput.py===
<code python>

import sys
#Load the widget
from PyQt4.QtGui import QWidget #This is a widget, not a window, and that makes a difference
from PyQt4.uic import loadUiType #We need this to dynamically load the .ui file we created in qt designer
from PyQt4.QtCore import pyqtSignature, Qt #Not sure what this signature thing is, but apparently it is great for buttons (signals/slots?)
import sys

(form, formbase) = loadUiType('readinput.ui') #this is the .ui file we want to show

class readInputWidget(QWidget, form): #in this class, we load the window, and assign actions to the buttons
def __init__(self, parent=None):
QWidget.__init__(self, parent)
self.setAttribute(Qt.WA_DeleteOnClose) #This doesn't seem to change anything if you delete it, but may be usefull for housekeeping
self.setupUi(self)

# read back the entire test string as a string with read()
filename = "config.txt"
try:
fin = open(filename, "r")
str3 = fin.read()
fin.close()
print "Contents of file %s:" % filename
print str3
self.inputBox1.setText(str3) #This is the line where we set the input box to display whatever was written to the config file last time

except IOError:
print "File %s does not exist!" % filename

@pyqtSignature("on_exitButton_clicked()")
def on_exitButton_clicked(self):
self.close()

@pyqtSignature("on_evalButton_clicked()")
def on_evalButton_clicked(self):
print 'This should echo our text:'
userinput = self.inputBox1.text() #This is the fantastic line of code we were waiting for! Make sure you have an input box by that name, and specify that it is text
print userinput
# a look at file handling in Python
# tested with Python24 vegaseat 29sep2005

# set up a test string
str1 =userinput

# let's create our test file by writing the test string to the working folder/directory with write()
# modifier "w" is for writing text, use "wb" for binary data like images
fout = open("config.txt", "w")
fout.write(str1)
fout.close()

def main():
from PyQt4.QtGui import QApplication
from PyQt4.QtCore import Qt
app = QApplication(sys.argv)
widget = readInputWidget()
widget.show()
return app.exec_()

if __name__ == "__main__":
sys.exit(main())

</code>
This uses the exact same [[User:Axiom/readinput.ui|ui file]] as above.

User talk:Danimo

2007-03-28T18:27:22Z

Axiom:

==CAPTCHAs that won't go away==
Aseigo [[Talk:Main_Page#Something_wrong_with_the_CAPTCHAs|suggested]] that I ask you about this. Everytime I make an edit, it claims that I am adding a URL, and wants me to do some math. Is it even supposed to do this to registered users? In any case, ''most'' times I am not adding a url at all, and I tire of the systems inordinate appetite for elementary arithmetic. Can this be fixed? Thanks. --[[User:Axiom|Axiom]] 20:27, 28 March 2007 (CEST)

User:Axiom/readinput.ui

2007-03-28T18:19:45Z

Axiom: /* readinput.ui */

==readinput.ui==

<code xml>

<ui version="4.0" >
<author></author>
<comment></comment>
<exportmacro></exportmacro>
<class>readInputWidget</class>
<widget class="QWidget" name="readInputWidget" >
<property name="geometry" >
<rect>
<x>0</x>
<y>0</y>
<width>351</width>
<height>108</height>
</rect>
</property>
<property name="windowTitle" >
<string>Read User Input Tutorial</string>
</property>
<layout class="QVBoxLayout" >
<property name="margin" >
<number>9</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<layout class="QHBoxLayout" >
<property name="margin" >
<number>0</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<widget class="QLineEdit" name="inputBox1" />
</item>
<item>
<widget class="QPushButton" name="evalButton" >
<property name="text" >
<string>Echo Text</string>
</property>
</widget>
</item>
</layout>
</item>
<item>
<layout class="QHBoxLayout" >
<property name="margin" >
<number>0</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<spacer>
<property name="orientation" >
<enum>Qt::Horizontal</enum>
</property>
<property name="sizeHint" >
<size>
<width>40</width>
<height>20</height>
</size>
</property>
</spacer>
</item>
<item>
<widget class="QPushButton" name="exitButton" >
<property name="text" >
<string>Exit</string>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
<pixmapfunction></pixmapfunction>
<tabstops>
<tabstop>inputBox1</tabstop>
<tabstop>evalButton</tabstop>
<tabstop>exitButton</tabstop>
</tabstops>
<resources/>
<connections/>
</ui>

</code>

User:Axiom/readinput.ui

2007-03-28T18:18:53Z

Axiom:

==readinput.ui==

<ui version="4.0" >
<author></author>
<comment></comment>
<exportmacro></exportmacro>
<class>readInputWidget</class>
<widget class="QWidget" name="readInputWidget" >
<property name="geometry" >
<rect>
<x>0</x>
<y>0</y>
<width>351</width>
<height>108</height>
</rect>
</property>
<property name="windowTitle" >
<string>Read User Input Tutorial</string>
</property>
<layout class="QVBoxLayout" >
<property name="margin" >
<number>9</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<layout class="QHBoxLayout" >
<property name="margin" >
<number>0</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<widget class="QLineEdit" name="inputBox1" />
</item>
<item>
<widget class="QPushButton" name="evalButton" >
<property name="text" >
<string>Echo Text</string>
</property>
</widget>
</item>
</layout>
</item>
<item>
<layout class="QHBoxLayout" >
<property name="margin" >
<number>0</number>
</property>
<property name="spacing" >
<number>6</number>
</property>
<item>
<spacer>
<property name="orientation" >
<enum>Qt::Horizontal</enum>
</property>
<property name="sizeHint" >
<size>
<width>40</width>
<height>20</height>
</size>
</property>
</spacer>
</item>
<item>
<widget class="QPushButton" name="exitButton" >
<property name="text" >
<string>Exit</string>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
<pixmapfunction></pixmapfunction>
<tabstops>
<tabstop>inputBox1</tabstop>
<tabstop>evalButton</tabstop>
<tabstop>exitButton</tabstop>
</tabstops>
<resources/>
<connections/>
</ui>

User:Axiom

2007-03-28T18:17:04Z

Axiom:

User:Axiom/demo.ui

2007-01-21T22:52:50Z

Development/Tutorials/Python introduction to signals and slots

2007-01-21T18:47:12Z

Axiom: /* Emitting signals */ It won't work unless you import sys first

{{warning|This tutorial is work in progress.}}

==Abstract==
The signal and slot architecture is design to simplify communication between objects. It's a fact that GUI programming is mostly event driven. The traditionally approach to event driven programming is to use callbaks. Callbacks have a number of limitations that Qt tries to solve with it's signal and slot architecture. The concept is that every object can emit signals. For example when a button is clicked it emits a “clicked()” signal. Signals does not do anything alone, but when connected to a slot the code in the slot will be executed every time the signal is emitted. In python every function is a slot. It's possible to connect one signal to multiple slots

==Prerequisites==
General understanding of the python programming language. No prior knowledge of QT is required.

==Connecting signals and slots.==
We use the QObject.connect() method to connect signals and slots.

<code python>
bool connect (QObject, SIGNAL(), callable, Qt.ConnectionType = Qt.AutoConnection)
</code>

The first argument is the name of the object that is emitting the signal. The second argument is the signal, and the third argument is the slot. The slot has to bee a python callable object. Note that only QObjects and objects inheriting from QObject can emit signals.

'''Example'''
<code python>
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

#First we create a QApplication and QPushButton
app=QApplication(sys.argv)
exitButton=QPushButton("Exit")

#Here we connect the exitButton's "clicked()" signals to the app's exit method.
#This will have the effect that every time some one clicks the exitButton
#the app.exit method will execute and the application will close.
QObject.connect(exitButton,SIGNAL("clicked()"),app.exit)

exitButton.show()
#Start the evnt loop
sys.exit(app.exec_())
</code>

==Emitting signals==
Only QObjects and objects inheriting from QObject can emit signals. To emit a signal we use the QObject.emit() method.

<code python>
QObject.emit (self, SIGNAL(), ...)
</code>

emit() is an object method, the self parameter is therefor automatically inserted by the python interpreter. The next argument is the signal we would like to emit, for example it could have been SIGNAL("myfirstsignal()") if we wanted to emit a signal with that name. The next parameters is optional parameters that can be sent with the signal, will come back to that in more detail later.

'''Example:'''In this example we have a class with a function "afunc" that emits the signal "doSomePrinting()". The class also have function "bfunc" that prints "Hello world". First we create a object of the class then we connect the "doSomePrinting()" to "bfunc". After that we call "afunc". This will result in the printing of "Hello World" to the standard output

<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def afunc (self):
self.emit(SIGNAL("doSomePrinting()"))

def bfunc(self):
print "Hello World!"

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("doSomePrinting()"),a.bfunc)
a.afunc()
sys.exit(app.exec_())

</code>

==Signals and slots with parameters==
The signal and slots mechanism is type safe. In C++ this implies that both the number of arguments and the type of the arguments in a signal must match the arguments in the receiving slot. In Qt's Signal and slots architecture the receiving slot can actually have fewer parameters than the emitted signal, the extra arguments will then be ignored. Because of pythons dynamically typed nature it not possible to do any type checking in advance. It is therefor important to make sure that the emitted object is of the expected type or of a type that can be automatically converted to the expected type. For example a python string will automatically be converted to QString. If we send a object of an incompatible type we will get an runtime error.

'''Example:'''
This example will create a slider and display it. Every time the value of the slider is changed the new value will be printed to the standard output. The references documentation for QSlider can be found [http://www.riverbankcomputing.com/Docs/PyQt4/html/qslider.html here], the valueChanged signal is inherited from [http://www.riverbankcomputing.com/Docs/PyQt4/html/qabstractslider.html QAbstractSlider]
<code python>
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

def printNumber(number):
print number

if __name__=="__main__":
#First we create a QApplication and QSlider
app=QApplication(sys.argv)
slider=QSlider(Qt.Horizontal)

QObject.connect(slider,SIGNAL("valueChanged(int)"),printNumber)

slider.show()
#Start the evnt loop
sys.exit(app.exec_())
</code>

==Python objects as parameters==
It's possible to send a python object of any type using PyQt_PyObject in the signature. This is recommended when both signal and slot is implemented in python. By using PyQt_PyObject we avoid unnecessary conversions between python objects and C++ types and it more consistent with python dynamically typed nature.

'''Example'''
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def send (self):
msg=[1234,"1234",{1:2}]
self.emit(SIGNAL("asignal(PyQt_PyObject)"),msg)

def recive(self,msg):
print msg

def p(msg): print int(time()-start),msg

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("asignal(PyQt_PyObject)"),a.recive)
a.send()

sys.exit(app.exec_())
</code>

==Short-circuit Signal==
PyQt4 have a special type of signal called a short-circuit Signal. This signal implicitly declare all arguments to be of type PyQt_PyObject. Short-circuited signals does not have argument lists or parentheses. Short-circuited signals can only connected to python slots.

'''The same example as above, using short-circuited signals. '''
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def send (self):
msg=[1234,"1234",{1:2}]
self.emit(SIGNAL("asignal"),msg)

def recive(self,msg):
print msg

def p(msg): print int(time()-start),msg

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("asignal"),a.recive)
a.send()

sys.exit(app.exec_())
</code>

==Signals and slots and threading==
To send signal across threads we have to use the Qt.QueuedConnection parameter. Without this parameter the code will be executed in the same thread.
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QThread):
def __init__(self):
QThread.__init__(self)

def afunc (self):
p("starting in a()")
self.emit(SIGNAL("asignal"))
p("finished in a()")

def bfunc(self):
p("starting in b()")
self.sleep(3)
p("finished in b()")

def run(self):
self.exec_()

def p(msg): print str(int(time()-start)) + "s",msg

if __name__=="__main__":
start=time()
p("starting in __main__")
app=QCoreApplication(sys.argv)
a=A()
a.start()
QObject.connect(a,SIGNAL("asignal"),a.bfunc,Qt.QueuedConnection)
a.afunc()
p("finished in __main__")

sys.exit(app.exec_())
</code>

<code>
Output:
0s starting in __main__
0s starting in a()
0s finished in a()
0s finished in __main__
0s starting in b()
3s finished in b()

without Qt.QueuedConnection the example will output:
0s starting in __main__
0s starting in a()
0s starting in b()
3s finished in b()
3s finished in a()
3s finished in __main__
</code>

==QueuedConnections==
[[Category:Python]]

User:Axiom/myskin.css

2007-01-15T01:37:13Z

Axiom:

/*
** HTML elements
*/

body {
margin: 0;
padding: 0;
text-align: center;
font-size: 0.8em;
font-family: "Bitstream Vera Sans", "Lucida Grande", "Trebuchet MS", sans-serif;
color: #535353;
background: #fff;
}

.clear {
clear: both;
}

/* general styles */

table {
background: white;
font-size: 100%;
color: black;
}

a:link, a:visited {
padding-bottom: 0;
text-decoration: none;
color: #0057ae;
}

a:hover {
text-decoration: underline;
}

a.title:link, a.title:visited, a.title:hover {
text-decoration: none;
color: #fff;
}

a:visited {
color: #644a9b;
}
/*
a.stub {
color: #772233;
}
a.new, #p-personal a.new {
color: #ba0000;
}
a.new:visited, #p-personal a.new:visited {
color: #a55858;
}
*/
h1, h2, h3, h4 {
text-align: left;
font-weight: bold;
margin-top: 1.0em;
color: #F7800A;
background: transparent;
}

h1 {
margin-top: 1.5em;
font-size: 1.7em;
}

h1.firstHeading {
margin-top: .5em;
font-size: 1.7em;
}

h2 {
font-size: 1.5em;
}

h3 {
font-size: 1.2em;
color: #e3ad00;
}

h4 {
font-size: 1.1em;
}

h5 {
font-size: 1.0em;
}

#right ul {
line-height: 1.5em;
list-style-type: square;
margin: .3em 0 0 1.5em;
padding: 0;
/* list-style-image: url(bullet.gif);*/
}
ol {
line-height: 1.5em;
margin: .3em 0 0 3.2em;
padding: 0;
list-style-image: none;
}
li {
margin-bottom: .1em;
}

hr {
margin: 0.3em 1em 0.3em 1em;
height: 1px;
border: #dddddd dashed;
border-width: 0 0 1px 0;
}

del {
color: #800;
text-decoration: line-through;
}

dt {
font-weight: bold;
font-size: 1.05em;
color: #0057ae;
}

dd {
margin-left: 1em;
}

p {
margin-top: 0.5em;
margin-bottom: 0.9em;
text-align: justify;
}

hr {
margin: 0.3em 1em 0.3em 1em;
height: 1px;
border: #dddddd dashed;
border-width: 0 0 1px 0;
}

legend {
background: white;
padding: .5em;
font-size: 95%;
}

input, textarea, select {
margin: 0.2em;
padding: 0.1em;
font-size: 125%; /* for poor aaron */
color: #000;
background: #fff;
border: 1px solid;
}

fieldset {
border: #ccc 1px solid;
}

li {
text-align: justify;
}

form {
margin: 0;
padding: 0;
}

hr {
height: 1px;
border: gray 1px solid;
}

img {
border: 0;
}

table {
border-collapse: collapse;
font-size: 1em;
}

th {
text-align: left;
padding-right: 1em;
border: #ccc solid;
border-width: 0 0 3px 0;
}

abbr, acronym, .explain {
border-bottom: 1px dotted black;
color: black;
background: none;
cursor: help;
}
q {
font-family: Times, "Times New Roman", serif;
font-style: italic;
}
/* disabled for now
blockquote {
font-family: Times, "Times New Roman", serif;
font-style: italic;
}*/
code {
font-family: 'Bitstream Vera Sans Mono', Courier;
background-color: #f9f9f9;
padding: 0 0.5em 0 0.5em;
border: 1px solid #b5cfe9;
}
pre {
padding: 1em;
/*/ border: 1px dashed #2f6fab;
color: black;
background-color: #f9f9f9;*/
font-size: 1.1em;
line-height: 1.1em;
overflow: auto;
}

/*
**The main area for structural Layout
*/

/* Main Header Navigation */
#header {
width: 100%;
color: #535353;
background: #eee;
border-bottom: 1px solid #bcbcbc;
}

#header_top {
margin: 0 auto;
padding: 0;
width: 60em;
min-width: 770px;
max-width: 45em;
vertical-align: middle;
color: #fff;
background: url(top.jpg) repeat-x bottom;
background-color: #0057AE;
min-height: 51px;
}

#header_top div {
margin: 0 auto;
padding: 0;
background: url(top-left.jpg) no-repeat bottom left;
min-height: 51px;
}

#header_top div div {
margin: 0 auto;
padding: 0;
vertical-align: middle;
text-align: left;
font-size: 1.7em;
font-weight: bold;
background: url(top-right.png) no-repeat bottom right;
min-height: 51px;
}

#header_top div div img {
margin:8px 0 8px 18px;
vertical-align: middle;
}

#header_bottom {
margin: 0 auto;
padding: 0.6em 0em 0.3em 0;
width: 60em;
min-width: 770px;
max-width: 45em;
vertical-align: middle;
text-align: right;
background: #eeeeee;
}

#location {
padding: 0 0 0 1.5em;
text-align: left;
line-height: normal;
font-size: 1.1em;
font-weight:bold;
float: left;
}

#location ul {
display: inline;
margin: 0;
padding: 0;
list-style: none;
}

#location ul li {
display: inline;
white-space : nowrap;
margin: 0;
padding: 0 1em 0 0;
}

#body_wrapper {
margin: 0 auto;
width: 60em;
min-width: 770px;
max-width: 45em;

}

#body {
float: left;
margin: 0;
padding: 0;
width: 60em;
min-height: 40em;
min-width: 770px;
max-width: 45em;
border: #dddddd solid;
border-width: 0 0 0 1px;

}

#main {
width: 100%;
padding: 10px;
text-align: left;
}

/* Container for the right content that gets floated right */
#right {
float: right;
margin: 0;
padding: 0;
width: 73%;
}

/*
** Left Navigation for Wiki
*/

#left {
float: left;
margin: 0;
padding: 0;
width: 25%;
}

/*
** Top Menu UL Based Menu
*/

#menu {
margin: 0 0 0 0;
text-align: right;
line-height: normal;
font-size: 1.1em;
font-weight: bold;

}

#menu ul {
display: inline;
list-style: none;
margin: 0;
padding: 0;
text-align: right;
}

#menu ul li {
display: inline;
white-space : nowrap;
margin: 0 0 0 0;
padding: 0 0 0 0;
text-align: center;
max-height: 1.6em;
}
#menu ul li a, #menu ul li.selected a{
padding: 0.2em 8px 0.3em 0;
}

#menu ul li a {
background: url(tab-right.png) no-repeat top right;
color: #5d5d5d;
text-decoration:none;
}

#menu ul li.new a {
background: url(tab-right.png) no-repeat top right;
color: #bbbbbb;
text-decoration:none;
}

#menu ul li.selected a{
background: url(taba-right.png) no-repeat top right;
border-bottom: 1px solid white;
}
#menu ul li span, #menu ul li.selected span {
padding: 0.2em 0.6em 0.3em 1em;
}
#menu ul li span {

background: url(tab-left.png) no-repeat top left;
}
#menu ul li.selected span {
background: url(taba-left.png) no-repeat top left;
color: #1357a4;
border-bottom: 1px solid white;
}

/*
** Menu CSS code goes in this section
*/
.menu_box {
padding: 0.7em 0 0.5em 0;
text-align: left;

}

.menu_box ul {
text-align: left;
margin-left: -10px;
}

.menu_box li {
list-style-type: none;
text-align: left;

}
.menu_box .active{
color: #cf4913;
}

.menutitle {
text-align: left;
margin: 0.6em 0 0 0;
padding:0;
color: white;
color: white;
background: url(block_title_mid.png) repeat-y right;
background-color: #0057AE;
}

.menutitle div {
margin: 0;
padding:0;
background: url(block_title_top.png) no-repeat top right;
}
.menutitle div h2 {
margin: 0;
padding: 0.2em 0 0.3em 0.5em;
line-height:1.2em;
font-size: 120%;
font-weight: normal;
color: white;
background: url(block_title_bottom.png) no-repeat bottom right;
}

/* Search Button Classes go here */
.menu_box form {
margin-top: 0.6em;
text-align:center;
}
.menu_box form #searchInput{
width: 8em;
border: 2px solid #dddddd;
color: #aaa;
font-size:75%
}
.menu_box input.searchButton {
/*confirm the colours used in here */
margin-top: 1px;
width: 4em;
background-color: #888a85;
color: #fff;
border: 1px solid #bcbdba;
font-size:75%
}

#footer {
width: 100%;
background: #eeeeee;
}

#footer_text {
margin: 0 auto;
padding: 1em 0 1em 3.5em;
width: 51.5em;
text-align: left;
color: #000000;
background: #eeeeee;
}

#footer a:link, #footer a:visited {
color: #4d88c3;
}

.printfooter {
display: none;
}

img.tex {
vertical-align: middle;
}
span.texhtml {
font-family: serif;
}

/* emulate center */
.center {
width: 100%;
text-align: center;
}
*.center * {
margin-left: auto;
margin-right: auto;
}
/* small for tables and similar */
.small, .small * {
font-size: 94%;
}
table.small {
font-size: 100%;
}

/*
** Diff rendering
*/
table.diff, td.diff-otitle, td.diff-ntitle {
background-color: white;
}
td.diff-addedline {
background: #cfc;
font-size: smaller;
}
td.diff-deletedline {
background: #ffa;
font-size: smaller;
}
td.diff-context {
background: #eee;
font-size: smaller;
}
span.diffchange {
color: red;
font-weight: bold;
}

div.floatright, table.floatright {
clear: right;
float: right;
position: relative;
margin: 0 0 .5em .5em;
border: 0;
/*
border: .5em solid white;
border-width: .5em 0 .8em 1.4em;
*/
}
div.floatright p { font-style: italic; }
div.floatleft, table.floatleft {
float: left;
position: relative;
margin: 0 .5em .5em 0;
border: 0;
/*
margin: .3em .5em .5em 0;
border: .5em solid white;
border-width: .5em 1.4em .8em 0;
*/
}
div.floatleft p { font-style: italic; }

/* rounded infobox */

.rbroundbox { }
.rbtop div { background: url(tl.png) no-repeat top left; }
.rbtop { background: url(tr.png) no-repeat top right; }
.rbbot div { background: url(bl.png) no-repeat bottom left; }
.rbbot { background: url(br.png) no-repeat bottom right; }

.rbtopwrap {
color: #fff;
background-color: #0071bc;
padding-bottom: 0.5em;
font-weight: bold;
text-align: center;
}

.rbtop div, .rbtop, .rbbot div, .rbbot {
width: 100%;
height: 7px;
font-size: 1px;
}

.rbcontent { margin: 0 7px; padding-top: 0.5em; }
.rbroundbox { width: 50%; margin: 1em auto; background-color: #dadde0;}

/* rounded codebox */

div.rtop, div.rbottom { display: block; }
div.rtop b, div.rbottom b { display: block; height: 1px; overflow: hidden; }
div.rtop b.r1, div.rbottom b.r1 { margin: 0 5px; background: #555753; }
b.r2 {margin: 0 3px; border-left: 2px solid #555753; border-right: 2px solid #555753;}
b.r3 {margin: 0 2px; border-left: 1px solid #555753; border-right: 1px solid #555753;}
div.rtop b.r4, div.rbottom b.r4
{ margin: 0 1px; height: 2px; border-left: 1px solid #555753; border-right: 1px solid #555753; }
div.rmiddle { border-left: 1px solid #555753; border-right: 1px solid #555753; padding: 0 5px; }
div.rcode p, pre { margin: 0; }
div.codebox { margin-bottom: 1em; }

div.rcode {
margin: 0;
padding: 0;
display: block;
overflow:auto;
font-family: 'Bitstream Vera Sans Mono', monospace;
white-space: pre;
}

.codebarbg {
background-image: url(codebarbg.png);
background-position: center right;
background-repeat: no-repeat;
background-color: #f1f1f1;
font-family: 'Bitstream Vera Sans Mono', monospace;
font-weight: bold;
font-size: 14px;
color: #555753;
padding: 0em 0.5em 0em 0.5em;
margin-bottom: 0.5em;
}

Development/Tutorials/Python introduction to signals and slots

2007-01-14T19:53:59Z

Axiom: /* Connecting signals and slots. */

{{warning|This tutorial is work in progress.}}

==Abstract==
The signal and slot architecture is design to simplify communication between objects. It's a fact that GUI programming is mostly event driven. The traditionally approach to event driven programming is to use callbaks. Callbacks have a number of limitations that Qt tries to solve with it's signal and slot architecture. The concept is that every object can emit signals. For example when a button is clicked it emits a “clicked()” signal. Signals does not do anything alone, but when connected to a slot the code in the slot will be executed every time the signal is emitted. In python every function is a slot. It's possible to connect one signal to multiple slots

==Prerequisites==
General understanding of the python programming language. No prior knowledge of QT is required.

==Connecting signals and slots.==
We use the QObject.connect() method to connecting signals and slots.

<code python>
bool connect (QObject, SIGNAL(), callable, Qt.ConnectionType = Qt.AutoConnection)
</code>

The first argument is the name of the object that is emitting the signal. The second argument is the signal, and the third argument is the SLOT. The third argument has to bee a python callable object. Note that only QObjects and objects inheriting from QObject can emit signals.

'''Example'''
<code python>
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

#First we create a QApplication and QPushButton
app=QApplication(sys.argv)
exitButton=QPushButton("Exit")

#Here we connect the exitButton's "clicked()" signals to the app's exit method.
#This will have the effect that every time some one clicks the exitButton
#the app.exit method will execute and the application will close.
QObject.connect(exitButton,SIGNAL("clicked()"),app.exit)

exitButton.show()
#Start the evnt loop
sys.exit(app.exec_())
</code>

==Emitting signals==
Only QObjects and objects inheriting from QObject can emit signals. To emit a signal we use the QObject.emit() method.

<code python>
QObject.emit (self, SIGNAL(), ...)
</code>

emit() is an object method, the self parameter is therefor automatically inserted by the python interpreter. The next argument is the signal we would like to emit, for example it could have been SIGNAL("myfirstsignal()") if we wanted to emit a signal with that name. The next parameters is optional parameters that can be sent with the signal, will come more back to that later.

'''Example'''

<code python>
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def afunc (self):
self.emit(SIGNAL("doSomePrinting()"))

def bfunc(self):
print "Hello World!"

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("doSomePrinting()"),a.bfunc)
a.afunc()
sys.exit(app.exec_())

</code>

==Signals and slots with parameters==
The signal and slots mechanism is type safe. In C++ this implies that both the number of arguments and the type of the arguments in a signal must match the arguments in the receiving slot. In Qt's Signal and slots architecture the receiving slot can actually have fewer parameters than the emitted signal, the extra arguments will then be ignored. Because of pythons dynamically typed nature it not possible to do any type checking in advance. It is therefor important to make sure that the emitted object is of the expected type or of a type that can be automatically converted to the expected type. For example a python string will automatically be converted to QString. If we send a object of an incompatible type we will get an runtime error.

'''Example'''
<code python>
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

def printNumber(number):
print number

if __name__=="__main__":
#First we create a QApplication and QPushButton
app=QApplication(sys.argv)
slider=QSlider(Qt.Horizontal)

QObject.connect(slider,SIGNAL("valueChanged(int)"),printNumber)

slider.show()
#Start the evnt loop
sys.exit(app.exec_())
</code>

==Python objects as parameters==
It's possible to send a python object of any type using PyQt_PyObject in the signature. This is recommended when both signal and slot is implemented in python. By using PyQt_PyObject we avoid unnecessary conversions between python objects and C++ types and it more consistent with python dynamically typed nature.

'''Example'''
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def send (self):
msg=[1234,"1234",{1:2}]
self.emit(SIGNAL("asignal(PyQt_PyObject)"),msg)

def recive(self,msg):
print msg

def p(msg): print int(time()-start),msg

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("asignal(PyQt_PyObject)"),a.recive)
a.send()

sys.exit(app.exec_())
</code>

==Short-circuit Signal==
PyQt4 have a special type of signal called a short-circuit Signal. This signal implicitly declare all arguments to be of type PyQt_PyObject. Short-circuited signals does not have argument lists or parentheses. Short-circuited signals can only connected to python slots.

'''The same example as above, using short-circuited signals. '''
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QObject):
def __init__(self):
QObject.__init__(self)

def send (self):
msg=[1234,"1234",{1:2}]
self.emit(SIGNAL("asignal"),msg)

def recive(self,msg):
print msg

def p(msg): print int(time()-start),msg

if __name__=="__main__":
app=QCoreApplication(sys.argv)
a=A()
QObject.connect(a,SIGNAL("asignal"),a.recive)
a.send()

sys.exit(app.exec_())
</code>

==Signals and slots and threading==
To send signal across threads we have to use the Qt.QueuedConnection parameter. Without this parameter the code will be executed in the same thread.
<code python>
import sys
from time import time
from PyQt4.QtCore import *

class A (QThread):
def __init__(self):
QThread.__init__(self)

def afunc (self):
p("starting in a()")
self.emit(SIGNAL("asignal"))
p("finished in a()")

def bfunc(self):
p("starting in b()")
self.sleep(3)
p("finished in b()")

def run(self):
self.exec_()

def p(msg): print str(int(time()-start)) + "s",msg

if __name__=="__main__":
start=time()
p("starting in __main__")
app=QCoreApplication(sys.argv)
a=A()
a.start()
QObject.connect(a,SIGNAL("asignal"),a.bfunc,Qt.QueuedConnection)
a.afunc()
p("finished in __main__")

sys.exit(app.exec_())
</code>

<code>
Output:
0s starting in __main__
0s starting in a()
0s finished in a()
0s finished in __main__
0s starting in b()
3s finished in b()

without Qt.QueuedConnection the example will output:
0s starting in __main__
0s starting in a()
0s starting in b()
3s finished in b()
3s finished in a()
3s finished in __main__
</code>

==QueuedConnections==
[[Category:Python]]

Talk:Welcome to KDE TechBase

2007-01-14T19:50:19Z

Axiom: Oxygen theme

User:Axiom

2007-01-14T19:34:23Z

Axiom: trying out the syntax highlighting. nice!