Re: how to externally trigger konq-e to refresh view

On Wednesday, 23. September 2009, Stefan Strobl wrote:
> Hi Uli
> 
> thanks for your prompt answer.
> 
> Uli Luckas wrote:
> > On Wednesday, 23. September 2009, Stefan Strobl wrote:
> >> What I would like to do is to somehow tell konq-e from another
> >> application XY to reload its current URL. This is of use if application
> >> XY generates and stors a html page locally and wants konqueror to
> >> display/reload it.
> >>
> >> Now, this is how I tried to do it and the problems I ran into:
> >> I thought I use the Unix system signal SIGUSR2 to do the signaling. In
> >> the file view.cc in the BrowserView constructor I'm registering my
> >> "protected: static void sigusr2_handler()" function for SIGUSR2 which is
> >> generally working so far. From this handler I thought of calling the
> >> public slot function reload() which is _not_ working because I cannot
> >> call this non-static function reload() from my static function
> >> sigusr2_handler(). From sigusr2_handler() I also cannot access "HTMLView
> >> *m_doc" for the same reason. On the other hand I cannot make
> >> sigusr2_handler() non-static because sigaction() would complain about
> >> that. I'm lost here. Why can't I access the data even though I'm in the
> >> same class?
> >>
> >> Any ideas what I'm doing wrong? Or maybe ideas about a better approach
> >> to make my application XY cause konq-e to reload its page?
> >
> > Hi Stefan,
> > there are a few problems here.
> > First and most important, there are strict semantics of what is allowed
> > to be done inside a signal handler. Keep in mind, that the signal handler
> > could have interupted the main flow of code at any point and must make
> > sure not to cause any unexpected modifications to the environment of the
> > interrupted code. Please take a look at any unix book and what it tells
> > you about signals.
> >
> > Second, non static methods need an object (an instance of the class) to
> > operate on, static methods, also called "class methods", can be called on
> > the class itself. Please take a look at any C++ book and what it tells
> > you about classes and objects and the difference thereof.
> >
> > Qt/Embedded has a mechanism called qcop for inter process communication:
> > http://doc.trolltech.com/3.3/qcopchannel.html
> > You can extend konq-e to listen for a qcop message which could then
> > trigger a reload.
> 
> I now understand that I need an Object to access reload() from a static
> function. I also understand that SIGUSR2 is asynchronous and may
> interrupt the process at the wrong time.
> 
> The other thing is that my application doing the signalling is not a
> graphical QT application but a C program. Do you think using a Unix FIFO
> could be an alternative or is it better to make my application XY a QT
> application to be able to use QCopChannel?
> 
Please keep the list CCed.

If you don't want to make your programm a qapplication, you could also send 
qcop messages by calling the qcop command line application via ::system().
As you sugested you can also use a FIFO or a socket for communication. In the 
browser, just make sure to use the event loop (QSocket/QSocketNotifier) for 
asynchronus notification on fifo events.

Regards,
Uli

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Uli Luckas
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