On Tue, 21 Nov 2017 10:46:06 +0100
"R.Wieser"  wrote:

> Lew,
>
> > Nope. They need a framework.
>
> Yes, *every* OS does.
>
> The question now is if I need to add it, or if its already delivered as
> part of the OS.

 In the most minimal installations of Linux there is no GUI at all
just a text mode command line interface.

> And if its already delivered as part of the OS, how do I determine which
> one is/ones are installed, and which one of them is activily used (I
> assume its not a good idea to just use several at the same time - if only
> to keep a consistant look-and-feel theme wise)

 If the installation includes a GUI along with window manager or
desktop environment then there will be at least one framework included in
the installation, often there are several pulled in by different
applications. The machine I'm currently using has Xaw3D (Athena), fltk,
GTK2, GTK3, MESA (OpenGL 3D graphics), Open Motif, QT4, QT5, SDL, SDL2 as
well as the low level X-Windows libraries installed and being used by
various applications - I might have missed some.

 The package manager included with the installation will give you a
list of installed packages which will include any and all GUI frameworks
installed - there's almost certainly a GUI interface to the package manager
installed too.

> And than going back to my origional question:
>
> "How to write a dialog in C for RP3 running LXPanel 0.9.3 ?"

 Pick a framework, read the documentation (there are tutorials for
most if not all of them) for that framework and proceed.

 The key takeaway here is that RPI-3 and LXPanel are not in the
least bit relevant except to note that LXPanel apparently implies GTK so you
will certainly have that installed. Once you have written your application
it can be compiled and run on any machine with GTK (or whatever).

 GTK is a popular framework used by a great many applications so
getting to know it is well worthwhile if you intend to write GUI
applications, so if I were you I'd go with GTK (whichever version you
have), type GTK tutorial into my favourite search engine and work through
the hits until I found one I was happy with.

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