Hello.

I am trying to use okular to read a local .pdf file, on my Linux system.

I should state that I compiled Qt from source, and all of KDE. For example, KDE Konsole I compiled and it works fine (URL was: https://download.kde.org/stable/applications/18.12.0/src/konsole-18.12.0.tar.xz )

I was using this okular version:

https://download.kde.org/stable/applications/18.12.0/src/okular-18.12.0.tar.xz

The compilation worked without an error too.

When I try to start it, I get this:

"org.kde.kwindowsystem: Could not find any platform plugin"

And there is some kde-widget or something with this text:

"Unable to find the Okular component: The shared library was not found."

To me this is not very helpful. So I suggest to improve this message and the
handling of this altogether.

First, it currently states "The shared library was not found", but WHAT
is this shared library? The name appears to be missing.

I would suggest to include the name - either in the same sentence, or in
a sentence below. I have more than enough space in that widget so hit
me with more information. :)

When I know the name of the .so at hand, it makes it easier to google 
too; right now it is A BIT DIFFICULT to google for "the shared library
was not found".

I don't know enough of the internals of qt, kde or okular to know what
is going on. Perhaps the problem is in qt? Perhaps in some other kde
component. I have no idea. So my second suggestion is to expand
on the error message a little bit.

For example, something like:

"Qt is handling .pdf support, so make sure that bla-lib and bla-something
are installed and working".

Or if it is another KDE component, passing that information would help
too. 

The more information I have, the higher the chance that I can resolve
this problem but right now I am a blind man tumbling about the complexity
of KDE. Evince works out of the box but I read about the latest change
in okular for annotation so I wanted to try this out.

The awkward thing is that I am absolutely sure that months before
okular was working fine so I know that I have been doing something
wrong; but there is no trivial way for me to find out what (I also
compiled okular from source before when it worked).

Thanks for reading and considering.

PS: The error message improvements shown above do not necessarily have
to be implemented 1:1 - what is more important to me is that this
information can somehow be passed to me in a simple way, no matter 
how it is to be done. Could be a notification during the build time
too; or additional checks there. But I think the widget showing more
information would be a very simple addition and wouldn't be too 
confusing for other users either, since all we would show is additional
information (e. g. why I suggested to use another sentence, but the
name could of course also be shown in the one sentence only. Not sure
if there is a limit in how many sentences you guys want to show ... :P)