Hi,

I am wondering. If I build application for linux using gtk2 widgetset for GNOME (or XFCE etc.) and send this program to my friend, then he can run it without any external librarys (of course if he have gnome too), this same thing on windows. But why when I build application on KDE interface I need some external libQT4Pas to run it and my friend need it too (he have KDE so all QT librarys too)? There is no libGTK4Pas so why exists layer libQT4Pas? What is difference between GTK and QT librarys?

Regards

GTK offers a plain C interface. QT only offers a C++ interface. FPC does not (fully) support directly calling external C++ libraries. LibQT4Pas offers a plain C interface to QT for use by FPC.

Jonas

GTK has a procedural C interface, it is exposed in the GTK libraries. The FPC compiler understands this interface.

Qt is written in C++, and exposes C++ classes in the Qt libraries. The FPC compiler does not know how to handle C++ classes. Therefor, a 'procedural' interface to the C++ needs to be made, and this is libQT4Pas. It is generated by a GCC.

Michael.

Just as I thought - it is object class thing. So if "FPC does not (fully) support directly calling external C++ libraries" there are plans to support it? This will be great

2012/1/29 Michael Van Canneyt :

Do other languages like python use the plain c interface, or C++?

how about something like ruby, lua, objective C, php ..

Lars wrote

Do other languages like python use the plain c interface, or C++? how about something like ruby, lua, objective C, php ..

:( i don't nderstand why one would want to apply interpreted script languages, al la BASIC, to today's tasks... sure, these are neat and "more modern" but they are still interpreted scripting languages :(

Krzysztof wrote

Just as I thought - it is object class thing. So if "FPC does not (fully) support directly calling external C++ libraries" there are plans to support it? This will be great

Maybe it is possible (or will be possible) to use C++ class, but I don't see light at the end of tunnel for eg override virtual routine from such C++ class which is possible by C interface or howto attach callback (event) from pascal to C++. So if it isn't possible then what's the point with C++ support ?

zeljko

I've understand that he asks how python bindings works then ? Probably same way as our libQt4Pas. You cannot use Qt python without python bindings for qt
- so no direct C++ usage.

zeljko

Lars wrote

Do other languages like python use the plain c interface, or C++? how about something like ruby, lua, objective C, php ..

No idea, but Python, ruby, lua and php do not generate real programs but instead are just scripts which run in a interpreter, which is immensely different from a real program.

A more close comparison to Pascal might be asking what Fortran, Cobol, Ada or other similar compiled languages do, and I think that all of those would need a C interface.

I know very well Java due to Android work, which cannot bind to anything directly. It requires a special format using plain procedures in a special way, so it is like a C interface, or a plan Pascal procedural interface. It is called JNI and it will never accept C++

Jonas Maebe wrote

GTK offers a plain C interface. QT only offers a C++ interface. FPC does not (fully) support directly calling external C++ libraries. LibQT4Pas offers a plain C interface to QT for use by FPC.

Can one statically bind the LibQt4Pas into a FPC program, thus not require to ship an external libqt4pas DLL/SO? If possible, that might solve the original posters problem.

i may have easily misunderstood the OP's post... i tend to read in literan english format... ie: if you say eggs are round, that is where i base my response unless it is very obvious that there is something else to consider which i point out ;

waldo kitty wrote

i may have easily misunderstood the OP's post... i tend to read in literan english format... ie: if you say eggs are round, that is where i base my response unless it is very obvious that there is something else to consider which i point out ;

I think that this question was pretty clear:

"Do other languages like python use the plain c interface, or C++?"

zeljko

Eh, I meant how does ruby, lua, objective c, and similar tools bind the C++ api. Do they use an automatic tool that converts QT C++ objects to procedural? or by hand, someone converts the objects to procedures and structs? Or do they use the c++ objects directly to python objects..

Krzysztof wrote

Just as I thought - it is object class thing. So if "FPC does not (fully) support directly calling external C++ libraries" there are plans to support it? This will be great

There are no plans to support it, since every C++ compiler uses it's own (incompatible) format, and G++ changes it format regularly, so I was given to understand.

Michael.

"Real Programmers"...

When you use pascal to build web programs you use templates, right.. so you are interpreting templates. When you read an INI file you are interpreting the INI file. Some pascals, safe ones, are interpreted. Like Oberon, or UCSD Pascal. When you parse an Edit.Text and check it to make sure there is not some user error on input, you are interpreting things. Compiled programs are not fully compiled, they always contain some run time interpretation. When you use regexes they are interpreted. When you use wildcards in search boxes they are interpreted. From my testing, CGI programs that are compiled binaries, are actually SlowER than PHP programs. I am no fan of PHP , but it is pretty fast.

True, but still interesting to know if Python objects are somehow compatible with C++ objects, as a kind of academic exersise.. how do they do it? Possibly they just bind to procedural API, but it would be cool if they somehow did it more effectively. I also mentioned Objective C in my request but I have no idea if objective c even has a QT binding..

That's good information and adds to the knowledge.. of how they do it. Cool.

There are no plans to support it, since every C++ compiler uses it's own (incompatible) format, and G++ changes it format regularly, so I was given to understand.

even with support for calling c++ methods,
the many inlined functions are still an issue

see light at the end of tunnel for eg override virtual routine from such C++ class which is possible by C interface or howto attach callback (event) from pascal to C++. So if it isn't possible then what's the point with C++ support ?

The C++ support in the compiler isn't advanced enough to even remotely think about that yet.

Regards,
Sven

Yes, there's only one thing which can put some light over it, and that is if qt nokia decides to create pure C bindings as separate packages (dlls) for qt libs .. but it won't happen .... so long live libQt4Pas

zeljko

given to understand.

I wouldn't say that there is no plan for C++ support as some code for this already exists in the compiler.
While it's true that different C++ compilers are incompatible to each other and that also G++ likes to change its formats now and then, the basic memory layout in G++ is rather stable. The biggest problems is getting this supported at all, interfacing with the C++ Std library and things like virtual methods, etc.

Regards,
Sven

The smoke wrapper http://techbase.kde.org/Development/Languages/Smoke is used by a lot of these languages. See also
http://lists.trolltech.com/qt-interest/2006-08/thread00721-0.html.

Smoke is actually a tool that generates runtime wrappers for c++ libraries. It supports virtual methods, multiple inheritance etc.

Ludo

Yes there's smoke but that's all... no docs - exactly nothing. I've tried to dig into and try to get out how to create simplest wrapper, lost 3-4 hours with result = 0.

zeljko

In layman's terms : what is the 'support level' required for this to even /start/ working at all(even if not perfect at first) and what is considered '100% supported' ? So that people who /know/ things (not me I'm afraid) can tinker it to make it better ?

L.

I don't know what you want to get at, but what currently works can be seen in the following test files:

http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/tests/test/cg/tcppcl1.pp?revision=16684&view=markup http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/tests/test/cg/tcppcl2.pp?revision=16684&view=markup

The corresponding C++ files are

http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/tests/test/cg/obj/cpptcl1.cpp?revision=15239&view=markup http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/tests/test/cg/obj/cpptcl2.cpp?revision=15239&view=markup

Basically this means that name mangling works and calling static methods of C++ classes. That's it currently. I had planned to extend the support a bit (you'll see my name in one of the commit messages), but I got sidetracked with other projects like NativeNT port, helper types and generics (not to mention my non-FPC-related projects).

Regards,
Sven

It seems to me that you could compile qt4pas.c (or what ever the source file(s) of libqt4pas.so is) into a qt4pas.o and just link them statically with {$link qt4pas.o} which then would leave out the requirement for libqt4pas.so to be distributed with any program using the qt interface. The gpl? license may or may not make that possible though.

Regards,

Andrew

This sounds interesting

Krzysztof wrote

> the qt interface. The gpl? license may or may not make that possible

the binding and Qt are LGPL

hm..this looks pretty interesting. Have you tried that ?

zeljko

i understood that to mean "when interfacing with dlls" or similar :?

Do other languages like python use the plain c interface, or C++? how about something like ruby, lua, objective C, php ..

AFAIK, Lua uses automatically generated plain C binding. When I looked at it, the binding generator consisted of the following parts:
1) A C++-based program to parse C++ source and extract

   required information as XML;

2) A Lua program to build plain C binding based on this XML
3) A CMake scripts to manage building of the above parts and generated binding itself.

The corresponding source code is hosted here:
https://github.com/mkottman/lqt

Wow, that's "something" ! :)
Few years ago in age of Kylix 3 Andreas Hausladen builded C bindings for Qt3 via doxygen which created xml files and then small app builded bindings from that xml files - even virtual methods overriding was supported. So if someone have enough doxygen knowledge it is possible to create automatic C bindings with some efforts.

zeljko