can kde themes be used to style multi platform (linux/windows) Qt4 applications ?
Yes, if you build/copy all dependencies.
This is not possible. Qt uses every platform's native API to render the widgets, hence platform specific themes cannot be applied on other platforms.
Since themes maybe third-party, it becomes more difficult.
If you're talking about Qt Styles(QStyle) that are used in traditional C++ KDE themes(non Plasma or ini themes) then yes you can do that to some extent, though you may have to adjust/fix some(or more) things since their mostly written with the KDE theme purpose in mind. One good example would be to fix or ensure the cross-platform compatibility(the theme might use additional platform specific libraries). Then there's also the licensing issue that you definitely have to take into consideration, since most of those themes are under GNU GPL.
If you're talking about Qt Stylesheets, you are out of luck, since currently KDE doesn't support any way of theming using Qt Stylesheets, thus you have no KDE Stylesheet themes to use.
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Do you have a clear explanation why they have chosen the core of the application to be a plugin like the other components, and not just a basic shared library?
I cannot see any clear advantages, besides the 'coolness' of the design.
I got an answer from the developers themselves:
Qt Creator doesn't aim to be an application framework. "Core" being a
plugin has mostly academical reasons, though e.g. one practical
advantage is that in that way the core of Qt Creator automatically has
a "version", and the check if a plugin is compatible with Qt Creator
is done the exact same way as with any other plugin dependencies. Also
the whole startup initialization (including the initialization of the
other plugins) is done the same way which leads to same concept and
there is less to learn.
As to "why" we can only guess. In their own documentation they state:
Qt Creator is extensible in various ways. For example, Qt Creator
architecture is based on a plugin loader, which means that all
functionality beyond plugin loading is implemented in plugins.
However, you can extend and tweak many parts of Qt Creator without the
need to resort to coding in C++ and implementing such a plugin.
So from this one could gather that this choice was made with extensibility in mind. I'm not sure if the answer to "why is the core a plugin?" is anything more than "why not?". If you are creating your application to be, as they say, a plugin loader, then why not keep it as "light" on functionality as possible and make the core a plugin as well.
Suggest a good widget toolkit to devlop GUI. I've worked with QT, GTK+ and X11, wikipedia shows a lot, is there anything better than than qt? To work with multi touch computing. I cannot start from the scratch with X11, and gtk is tough, QT is easier, but is there anyother toolkits like gtk or frameworks like qt to server better?
I'd suggest you to use the richest possible GUI framework. This way you will eliminate lots of unnecessary code and reuse existing functionalities.
If you'll take above into consideration, you'll have two options (dropping GTK because of complexity as you say, and bunch of other less maintained and less popular toolkits):
Qt
WxWidgets
I've worked with both and both share somewhat similar concepts, but IMHO Qt is better documented, better maintained, and is used by far more developers than WxWidgets, plus it have more sophisticated tools like QtCreator, etc.
On the other hand I like that WxWidgets has manual programming approach, where you're practically forced to build the GUI from code.
One very important thing to mention:
Qt has support for embedded
Linux, eliminating the need for
X11.
Some literature:
WxWidgets Compared To Other Toolkits
...and other Google results
I am going to develop a new GUI for an existing C++ application. The application works on Windows and Linux, and the communication with GUI is through client/server.
What are the pros and cons between Eclipse RCP and Qt?
Some pros of Qt:
C++ stuff will generally perform better; however, this is arguable.
Qt is the base of Meego, the mobile platform sponsored by Intel, AMD and others; however, its current momentum seems not too high to me. This means you can also create applications for various mobile and generally embedded devices
There are a lot of Qt-based applications out there.
It has a WYSIWYG designer.
Good for small to large projects especially because of QtQuick, which allows the creation of small applications in no time and with almost zero knowledge about C++
Qt has an amazing wrapper in Python called PyQt (there is also the PySide of course), which allows rapid development and slick prototyping. People often use PyQt (or PySide) for the UI-side of a Qt application because of that. You can of course combine with ease Python and Qt in the same application taking advantage of all their strengths (but also weaknesses). This allows relatively fast and smooth development cycles even for large projects
Some cons of Qt:
The code of Qt-based applications make use of some elements that are not part of C++, which have to be converted into C++ by a special preprocessor called moc (Meta-Object Compiler) prior to the actual compilation. You and your build system have to take that into account.
Nokia (former owner of Qt, since it acquired Trollech) has sold it to Digia. However, this does not imply their involvement in the development of the open source Qt has changed.
Some pros of Eclipse RCP:
Eclipse RCP is far more than a graphical toolkit:
It sports a plugin-based architecture that can help distributing functionality among different components (plugins) and keeping control over dependencies among such components (plugins). Eclipse plugin system relies on their own implementation of the Java component system specification called OSGi.
It provides a mechanism to enable decoupled application extensibility called extension points.
There are many Eclipse plugins that you can use in your application and many of them have distribution licenses that are friendly to commercial products.
It has a WYSIWYG designer.
Some cons of Eclipse RCP:
Eclipse uses a custom windowing toolkit called SWT; on each platform it relies on the native graphical layer. On Linux, it relies on Gtk+ (although it's also possible to use Motif), which in my experience (and other's) has performance problems, mostly with widgets that are updated at high rates. Actually many of us embed Swing elements in Eclipse RCP applications to overcome performance problems while keeping Eclipse's extensible architecture; this, however, can bring integration problems. There's a version of SWT that uses Qt as backend, but its incorporation into Eclipse's codebase seems stagnated since October 2010.
Startup time (understood as the time elapsed since the application is launched until it shows up a window) of Eclipse RCP applications can be very long.
If you intend to integrate C++ stuff with Java by means of JNI, be aware that some people find it difficult.
Eclipse has lots and lots of bugs. Eclipse's bugzilla is a very useful resource for the RCP developer.
The more you want you Eclipse RCP application's look&feel and behaviour to differ from Eclipse IDE, the more troubles you will get into.
Eclipse RCP development has a big learning curve, in my opinion.
Using Eclipse RCP for small projects is basically a suicide (unless you are restricting yourself to only creating a plugin or similar). It is meant for medium to large and very large projects due to the complexity of its infrastructure, resource requirements and the above mentioned steep learning curve.
Eclipse RCP is not for mobile development because...it's RCP (Rich Client Platform). If you want to go mobile, this is not for you.
Both their distribution licenses (LGPL/GPL/commercial for Qt, EPL for Eclipse) are flexible enough for most uses, in my opinion. Nevertheless, I am not a lawyer, so I may be mistaken about that.
And of course, other factors like the experience of the developers, their technical skills, the size of the team, concrete requirements, etc, should be taken into account.
BTW, I have much experience in Eclipse RCP but only theoretical knowledge on Qt, so I may be biased/mistaken in my statements.
Now that Qt has an LGPL license I would choose Qt any day of the week over Eclipse RCP.
I have used both to create fairly complex applications.
Since you can use eclipse to develop c++, I am assuming that we are comparing mostly swt/jface vs Qt, and not the eclipse development environment itself.
Some things I have noticed having used both:
1) Qt has better documentation and samples
Other than some half-baked examples on the web, I could find little useful eclipse documentation.
2) Qt has a lot more 'professional' users
There are many professional companies out there using Qt as their UI framework. Given it's three platform support (Windows, Linux, Mac), it is very flexible, and has a lot of backing.
3) Qt tends to be more complete and mature -
Using Eclipse I noticed that quite often the controls, and packages that were available were only partially done, and not quite complete. They were typically developed for someone's use, and only coded as far as that. Qt's controls were almost always a complete design.
4) Styling.
Both Qt and Eclipse render using local platform libraries, so your UI will 'look' like other UIs on the platform you are running on (i.e. Linux vs Windows). However, Qt also provides fairly sophisticated styling functionality that allows you to easily alter the look of any control, and gives you much more control over the look of your application.
With the new declarative language (Qt 4.7.*) you are approaching WPF level of control which is really amazing.
5) UI Designer:
Qt has a much richer Designer that allows you to layout your form, and do basic testing without having to compile any code. The designer also gives you the capability to add interactions between the controls on your form. Ex. Click this button - disable this option
Eclipse also has a form designer, although my experience with it is limited. I did try to use it a couple of times with very limited success. Finally I coded every form by hand through code. That is painful.
6) Interfacing with existing source code
If you don't have this problem, then you are very lucky. Because Qt is c++ based it integrates seamlessly with legacy C and C++ code. Integrating Java and C is not easy.
7) Drawing Libraries
I tried coding some hand-drawn shapes using the swt libraries and was forced to bypass large parts of the swt drawing library, because of the cludge that was in there. Using Qt to do something similar was no trouble at all.
8) Tree and List Models
Eclipse does provide some nice out of the box functionality for propagated data into trees, and lists and things. It is almost as good in Qt, although a little trickier to set up.
9) Application Layout
Eclipse provides some nice functionality to manage 'view's (dock panels), and 'perspectives' (workflows) that if you decide to use them makes life nice and easy. Qt requires you to do this yourself. Qt does have dock panel functionality, but when building a rich application you have to set this up yourself.
Extra Note:
Qt has also provided some extra libraries to support things like xml, etc... So this helps bridge the gap a little between c++ and java for things like this.
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Can someone suggest what's the best uses for those libraries today? Is it just GUI, or do they have database, XML, networking, threading, etc support too?
I was reading about them, and considered starting to learning/using one of them.
What is the most common one? What's the difference between them? Why would you choose one over the other?
As you seem to primarily target Linux, then the choice mostly depends on the programming language you want to use.
If you code in C, then obviously go for GTK+
If you code in C++, go for Qt, otherwise you will need Gtkmm (a C++ wrapper over GTK+)
If you code in Python, both GTK+ and Qt have bindings for the language: see PyGtk, PyQt and PySide (the one launched by Nokia themselves).
If you code in Java, Qt is no more a viable option imho as Nokia discontinued Qt Jambi (the Java bindings for Qt).
Also, Qt is more top-notch regarding its scenegraph QGraphicsScene API, its scripting engine built over Javascript Core (the engine powering WebKit), its state machine and animations framework, and the declarative UI.
GTK+ doesn't offer that much although you can use Clutter alongside with it.
If you're specifically looking into DB, XML (GTK+ has a parser for a subset of XML) and threading (GTK+ has GLib) features then Qt will offer all that in QtSql, QtXml and QtConcurrent.
All in all, I would say Qt is a sure choice. But GTK+ is very capable as well.
I'm not sure you will get a crystal clear answer for your question, which explains why some people keep preferring Gnome over KDE or vice-versa. Choose what works best for you.
PS: I you plan to also target Symbian, then go for Qt.
EDIT: Something that is also great with Qt is QtWebView: it brings Chromium into your Qt application to display web content. Others are embedding web content into their application using for instance Awesomium or Berkelium.
I've used GTK+, QT and wxWidgets before. Here's a brief summary:
For my first cross platform UI project I decided to go for wxWidgets mainly because at the time the license wasn't as restrictive as QT's (QT was GPL and only for Linux) and it had platform specific UI (unlike GTK). The project worked out well but there were quite a few glitches getting it to compile and run properly in other platforms - sometimes some events were fired up differently and such. Also GDI in wxWidgets was pretty slow.
Next I used GTK for a different project in python. For this I used the python bindings and everything worked out more or less smoothly. I didn't quite like the fact that the UI didn't look native on Windows and Mac and also when you launch a GTK+ app it always debug outputs loads of CRITICAL warnings which seem fine to ignore. :S
Finally, I did a very simple QT project now that Nokia has acquired it and was brilliant. The best of the three. First off, if you're not an old schooler who prefers VI or Emacs, QtCreator is brilliant. I really love VI and used it for years but I much prefer QtCreator for C++ QT projects. Regarding the library I also liked a lot the documentation and the APIs provided. QT has a concept of slots and signals which introduce new C++ keywords and a preprocessor. Basically, after reading a tutorial you'll get it easily and will start to love it. I'm now doing iPhone dev and it does feel a bit like Cocoa's/Interface Builder's UI paradigm.
Summary: I'd go for QT hands down. The license is pretty good and the SDK and documentation really nice.
I have never used GTK, but from my personal experience using Qt:
It is much more than a simple GUI. It's a whole application framework. I used to think of it as the Java libraries for C++. It provides all you mention -- database, XML, networking and threading, and more. It also provides things such as containers and iterators, and counterparts to a number of boost libraries.
The thing that impressed me most when starting to use Qt was the extremely extensive documentation. You get a program called Qt Assistant, which provides fully indexed and searchable API documentation on your desktop, as well as numerous code examples and tutorials. I found it made a big difference in searching the web each time for API info. Very quick access when you need to remember a method signature.
I am not sure which is most common; that's probably hard to measure accurately. They're certainly both popular. As Gnome is the default desktop of Ubuntu, and Gnome sits on top of GTK, it obviously has widespread usage. Of course, KDE is very popular as well. Nokia is heavily pushing Qt in the mobile space -- their Maemo OS, used on the new N900 for example, is soon to switch to Qt as the default toolkit (currently it is GTK.) I believe Qt will also soon become the default toolkit for Symbian OS.
I have not used Qt Creator, but I have heard many good things about it. It is a C++ IDE with obvious heavy integration with Qt. It also has fake vim emulation which is always nice if you like that kind of thing!
Qt uses qmake for build configuration. I found this much nicer than having to write your own makefiles. I do not know what GTK uses for building.
A couple of things I found a bit offputting with Qt at first was its big uses of preprocessor macros. The signal/slots system provides a nice mechanism for event/message passing in your application, but it does feel a bit like magic that may not be easily portable to another toolkit if you ever want to. Also, the moc (meta-object compiler), while I'm not entirely sure what it does, also feels a bit too much like magic going on behind the scenes.
All in all, though, I would recommend Qt, particularly if you are learning. It has really amazing documentation and a nice IDE, and busy forums. You'll be able to build C++ apps very rapidly with it, particularly with the QML coming in 4.7.
It probably depends on what you want to do. I would recommend Qt, because it's more than GUI, it has nice Python bindings (so does Gtk), and GUI libraries themselves are (subjectively speaking) more pleasant then Gtk.
Gtk is on the other hand more common in linux world, so you can probably get more help on the web. Reason for widespread of Gtk probably has more to do with Gnome and Ubuntu, rather then technical merits, but if you want you software to blend nicely with those two, you'll achieve that more easily with Gtk.
Qt for one sure has solid DB, network, threading support etc... It does a lot more then just cross-platform GUI (and it does most of it quite well).
I'd recommend it over GTK+.
Qt. It's not only object oriented, is "good" object oriented.
It's based on a "subset" of C++ that doesn't rely on the obscurity of C++ (but you are allowed to stick with them, if you fancy masochism ;) ).
It has a strong momentum now that Nokia bought it (actually Nokia did ~2/3 years ago). It's going to be in all Nokia AND Intel mobile devices (smartphones, netbooks, tablets).
It's the backbone of KDE, so it's very mature, but it's designed in a very flexible way, that makes it possible to support TODAY all the latest "cool stuff" that a more-then-just-GUI framework should have.
Go for it.
Just adding QT advantages to other answers.. QT has great documentation, its own IDE & GUI creator and enhances C++ with some new concepts like slots/signals (basically events).
I am not a GTK developer, so I can't compare those to the GTK world :(
It also looks like Nokia is about to use Qt everywhere, like on Maemo
If you want your app to run on iOS, Android, Blackberry, other mobile platforms, Windows, Mac OSX, and Linux, use Qt.
qt-project.org
I'm writing an application that is currently a pure QT4 app. It is designed to run cleanly on both Linux and Windows.
However I plan to integrate it a bit into KDE in future and here come the problems with localization/translations.
QT4 uses its own tr()/tr().arg().arg() mechanism and .ts/.qm files.
KDE4 uses gettext and i18n/i18np mechanism and .po files.
How, easily, can I use KDE4's mechanism in my QT4 application without having to closely integrate it with KDE now (apparently making it non-runnable on Windows)?
Is it at all possible?
Thanks!
Starting version 4.5, Qt will support both .po and .xliff;
http://doc.trolltech.com/4.5/qt4-5-intro.html#qt-linguist-improvements
I think you will need to just pick one and go with it, if it is a cross platform app, I'd go with QT's method. The reason why is that KDE wraps it's internationalized string with i18*() macros and QT uses tr() macros, since a macro can't produce another macro, there is no way unless you have #ifdef's all over your code, or a massive string table...both of which suck.