QT_PLUGIN_PATH (Re: Install kimgio plugins in the Qt image format plugins dir)

[Brad Hards]

On Saturday 27 October 2007 09:26:43 am Andreas Pakulat wrote:
> On 27.10.07 09:14:34, Brad Hards wrote:
> > On Saturday 27 October 2007 02:51:41 am Thiago Macieira wrote:
> > > - make it configurable via -D switch in the cmake command-line
> > > - default to something inside ${CMAKE_INSTALL_PREFIX}
> > > - print at the end of configure that you need to set QT_PLUGIN_PATH
> > > - do not check Qt's plugin path, ever
> >
> > My concern is that this will cause breakage at run-time (when QCA can't
> > find its plugins, it doesn't really do much), because people won't set
> > the plugin path, or will change it to something else when they install
> > kdelibs to a different prefix.
>
> How about a warning if QCA can't find _any_ plugin telling the user to
> check what he has in his QT_PLUGIN_PATH?
OK, but how? QCA has no GUI. 

> > Why do you think that we shouldn't expect people who build from source to
> > be able to install it to the same place that they installed Qt?
>
> Because they might want to use their system Qt.
And they can. If they also want to use QCA, they can either use their system 
QCA, or they can install QCA to the default location (i.e. under the Qt 
plugin directory), or if they don't have install privileges, they can install 
to another location and set a magic environment variable.

The simplest thing for the user is to use system QCA. The next most easy is to 
sudo the installation. Setting environment variables is the hardest.

I proposed a solution, which Thiago counterproposed an option without 
explaining why my solution isn't OK.

> > If users are reliant on system Qt (i.e. they don't use qt-copy), then why
> > not expect them to also use the system QCA?
>
> Well, because if you want to start hacking on QCA that won't work. Also
> currently the tutorials on techbase tell people to build kdesupport,
> which includes QCA and quite some people fail at that stage because QCA
> can't write to /usr/. Of course they could also build qt-copy, but thats
> not required and building qt-copy is quite some extra effort.
So if I add a CMake option for plugin installation, and fix the documentation 
to tell people about it, will everyone be happy?

Brad