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<h2>Frequently Asked Questions</h2>
<ol>
<li><a href="#faq-menutext">Why is there no menu text in my program's menus?</a></li>
<li><a href="#faq-menutext">Why doesn't pykdedocs have menus?</a></li>
<li><a href="#faq-icon">How do I set the icon for my program?</a></li>
<li><a href="#faq-logo">How do I set the logo in the "about application" dialog box?</a></li>
<li><a href="#faq-linkclick">Nothing happens when I click a link in KHTMLPart</a></li>
<li><a href="#faq-kapp">My program doesn't use KApplication ...</a></li>
<li><a href="#faq-kapperror">What is "QWidget: Must construct a QApplication before a QPaintDevice"?</a></li>
<li><a href="#faq-nomain">My program doesn't have KMainWindow (or descendant) ...</a></li>
<li><a href="#faq-exit">My program works, but crashes when I quit</a></li>
<li><a href="#faq_init">What is "underlying C/C++ object deleted"?</a></li>
</ol>
<hr>
<p> <b name="faq-menutext">Why is there no menu text in my program's menus?</b></p>
<p> <b name="faq-menutext">Why doesn't pykdedocs have menus?</b></p>
<p>
pykdedocs should display both a traditional menu bar (File, etc) and toolbar with icons.
Your application, if you've written it to display a menubar (see the 'Getting Started'
tutorial), should also display its menus.
</p>
<p>
One reason menus don't display text (you'll find the icons are there and the menus function -
they just don't display any text) in PyKDE4 for KDE 4.0.0 and 4.0.1 is that both KDE versions
default to the 'Oxygen' theme, and PyKDE4 won't display menu text correctly with that theme.
</p>
<p>
To display menu text in pykdedocs or your application, you need to change the theme. If
KDE4 is your principle desktop application (not KDE4 running under KDE3, as in SuSE 10.3,
for example), you can use Desktop Configuration or the Control Center to change the theme.
</p>
<p>
If you're running SuSE 10.3 or a similar distribution that uses KDE3 for the desktop but
allows you to run KDE4 applications, you need to run the following command at the
command line (in a konsole, for example):
</p>
<pre>
kcmshell4 style
</pre>
<p>
That should pop up a window that displays the style control module which will allow you
to change the theme (to 'Plastique', or 'CleanLook', for example). If kcmshell4 isn't in
your path or isn't installed, you'll need to locate it or install it to change the theme
for systems where KDE4 isn't the principle desktop.
</p>
<hr>
<p> <b name="faq-icon"><b>How do I set the icon for my program?</b></a></b></p>
<p>
Your program should subclass KMainWindow (or KXmlGuiWindow, or KParts::MainWindow). If the
name of your instance is "mainWindow" then add:
</p>
<pre>
mainWindow.setWindowIcon (KIcon (<icon name or path>))
</pre>
<p>
Or inside the main window constructor:
</p>
<pre>
self.setWindowIcon (KIcon (<icon name or path>))
</pre>
<hr>
<p><b><a name="faq-logo">How do I set the logo in the "about application" dialog box?</a></b></p>
<p>
The method that allows you to set the logo shown in the "About Application" dialog box
from the Help menu is:
</p>
<pre>
KAboutData.setProgramLogo (image)
</pre>
<p>
but there are several problems with using this. First, the image must be contained within a QVariant,
and with PyQt4, the only method call available to put a QImage inside a variant is
</p>
<pre>
QVariant (int, void*)
</pre>
<p>
where the second parameter has to be an actual C++ pointer to void. The int is an int
equivalent of the enumerator QVariant.Image. There are two possible ways to accomplish
this. The first is to use the PyKDE4 predefined method:
</p>
<pre>
from PyKDE4 setprogramlogo import setprogramlogo
...
image = QImage (<path to your image file>)
aboutData = KAboutData (<arguments>)
setprogramlogo (aboutData, image)
</pre>
<p>
The alternative is to duplicate the setprogramlogo code in your file:
</p>
<pre>
import sip
...
image = QImage (<path to your image file>)
aboutData = KAboutData (<arguments>)
vptr = sip.voidptr (sip.unwrapinstance (image))
vtype = int (QVariant.Image)
aboutData.setProgramLogo (QVariant (vtype, vptr))
</pre>
<p>
Of course you need to do the required PyKDE4 and PyQt4 imports as well, which
aren't shown here.
</p>
<hr>
<p><a name="faq-linkclick"><b>Nothing happens when I click a link in KHTMLPart</b></a></p>
<p>
Actually, something does happen - you just have to figure out how to connect to it. KHTMLPart
itself doesn't handle link clicks. The signal emitted when a link is clicked comes instead
from a KParts.BrowserExtension that your KHTMLPart instance already owns. You connect to it
like this:
</p>
<pre>
self.htmlpart = KHTMLPart (self)
self.extension = self.htmlpart.browserExtension ()
self.connect (self.extension,
SIGNAL ('openUrlRequest (const KUrl&, const KParts::OpenUrlArguments&, const KParts::BrowserArguments&)'),
self.slotOpenURL)
</pre>
<p>
The slot you connect to then has to hand the link's URL back to KHTMLPart to load. However, before doing
that, you also need to determine the mime type of the content at the link. KHTMLPart only displays HTML,
not .pdf or .tar.gz files (actually, it will display those, but as binary). One way to check is:
</p>
<pre>
mimetype = KIO.NetAccess.mimetype (url, None)
if mimetype != "text/html":
<insert code to handle non-HTML here>
</pre>
<p>
KIO.NetAccess.mimetype is slow and it's also synchronous (you have to wait for it to complete before
moving on with the rest of your code). There are asynchronous KIO.Job ways of determining the mime
type. If you expect a lot of local files (as pykdedocs does), it may be faster to check for those
first using os.path.exists () and checking for a ".html" extension.
</p>
<hr>
<p><b><a name="faq-kapp">My program doesn't use KApplication ...</a></b></p>
<p>
That's probably not a good thing. Most of KDE relies on the existence of a KApplication object,
and most KDE code won't work without either a KApplication or KUniqueApplication instance.
</p>
<p>
QApplication <b>can't</b> be substituted for KApplication, either.
</p>
<p>
See the next question for what happens when you don't have a KApplication.
</p>
<hr>
<p><b><a name="faq-kapperror">What is "QWidget: Must construct a QApplication before a QPaintDevice"?</a></b></p>
<p>
Your application hasn't created a KApplication or KUniqueApplication instance. See
the previous question.
</p>
<p>
Note that the error message comes from Qt, so it refers to QApplication, but for PyKDE4,
KApplication is what you have to use.
</p>
<hr>
<p><b><a name="faq-exit">My program works, but crashes when I quit</a></b></p>
<p>
Does your program use KMainWindow (or a KMainWindow subclass, like KXmlGuiWindow or
KParts.MainWindow) as its main widget?
</p>
<p>
If it doesn't, that's likely the cause of the crash (see next question). If it does,
it may be a PyKDE4 bug and should be reported.
</p>
<hr>
<p><b><a name="faq-nomain">My program doesn't have KMainWindow (or descendant) ...</a></b></p>
<p>
That's not as big a problem as not having a KApplication instance, but it may still cause a problem.
The shutdown code (run when your program exits) more or less expects a KMainWindow (or KMainWindow
subclass like KXmlGuiWindow or KParts::MainWindow) to own the objects to be destroyed at exit.
</p>
<p>
Not having a KMainWindow or similar class that "owns" the GUI can lead to crashes at exit, as
objects are not destroyed in the proper order. This is more of a problem in PyKDE than in KDE
itself - it may work fine in C++, but may not work in Python.
</p>
<p>
From my perspective, troubleshooting exit code problems is nasty and fixing them reliably is
not alway possible - what works for one situation may cause others to fail. It's simpler just
to subclass KMainWindow when writing your application.
</p>
<hr>
<p><b><a name="faq_init">What is "underlying C/C++ object deleted"?</a></b></p>
<p>
You've probably subclassed a PyKDE4 or PyQt4 class, but you forgot to call the original class's
__init__ method. The error is caused by doing something like this:
</p>
<pre>
class WidgetSubClass (QWidget):
def __ init__ (self, parent):
self.parent = parent
def someOtherMethod (self):
...
</pre>
<p>
What you need to do is
</p>
<pre>
class WidgetSubClass (QWidget):
def __ init__ (self, parent):
QWidget.__init__ (self, parent) # don't forget this !
self.parent = parent
def someOtherMethod (self):
...
</pre>
<p>
and make sure you pass "self" as the first argument.
</p>
<p>
The QWidget__init__ call (or whatever is equivalent in your code) doesn't have to be the first
statement in your object's __init__ method, but it has to be there. And it has to be there
before you start attempting to use the parent class's methods.
</p>
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