Do you use Qt and why do you use it?

Question

Pros. and cons? how long do you use it? What about jambi?

Answer 1

I've used Qt on a couple of projects I did in c++ on several platforms over a period of seven years. I think it works pretty well and definitely was quicker for me to develop a decent GUI app on the Mac than plodding through a language I didn't know (Objective-C) at the time.

I think the signal/slot mechanism is a bit funky but isn't horrible. Once you're use it for a bit, it's not a show stopper. The connection stuff is easy to bungle up (or at least it was) and it's always good to check the return on those because your app will go merrily on its way and not tell you that it didn't work.

I've never used jambi.

Answer 2

Qt is a very nice library, but it has an expensive per-seat developer license, so it's not always useful for all projects.

Answer 3

On C++ your only other alternatives are MFC and wxWidgets. QT / wxWidgets is largely a personal preference. I do think QT is a clean design with good documentation.
QT costs about one month of developer salary if you aren't using it for GPL.

Answer 4

I have been using Qt for several years now for commercial development and have been very happy with it.

One of the nice things with Qt is that it provides a large set of libraries as well as the GUI stuff (eg XML parsing, threads, networking), all in a consistent style and all multi-platform. This means we rarely need to use other libraries, though we do use boost for some things.

Another very important factor for us was internationalization. In a previous, MFC based application we had to maintain 2 localized versions, for the two languages we support. In our Qt based app we just have the one version.

• The Qt translation system, using linguist is easy to use and makes supporting multiple languages easy (of course you still have to translate the strings which is a lot of work!)
• The GUI layout system where the widgets resize themselves according to a layout makes everything much easier. In different languages the length of the strings are different. With fixed size widgets (like MFC) each dialog needs to be adjusted for each language, otherwise parts of labels get cut off. With Qt they resize themselves. Of course, there are cases when it does not work exactly right but it still makes everything much easier.
• QString does everything in Unicode and handles the conversions from different codecs very easily.

One thing that has been very valuable is the access to the source, although e this is certainly not unique to Qt. On several occasions the ability to check the Qt source has explained some strange behaviour or given a clue how to achieve something.

We have found a few bugs in Qt, some of which have been fixed after reporting to Trolltech. In other cases they have suggested a work around. These have all been fairly obscure and not had a major impact on our development.

One of the main downsides to Qt would be the lack of 3rd party libraries for use in commercial applications. However, Qt is fairly complete so for us it has not been a big problem, though that will depend on which type of application you are developing.

I have not used Jambi either.

Answer 5

I have been using Qt for over two years now.

Things I like on Qt are:

• Easy GUI programming (compared to MFC), Qt Designer
• Nice container classes
• Nice graphics scene framework
• Excellent documentation with useful examples
• Translation support
• Good technical support

I can highly recommend the Qt Developer Days. If you have a chance to take part, then do it! Lots of nice and very interesting talks there.

Answer 6

I used Qt in a previous job. I'd only had the absolute briefest of contact with Qt several years prior to that, so I was pretty much a Qt newb.

When I started I was told to choose my language and environment, but cross-platform support was desirable. I tried Qt and Java, and even gave C# a go just for the heck of it. I gave myself two days to evaluate each option.

Maybe I was slightly biased with my history as a C++ developer, but after spending time on each option Qt was the only one that showed any hints at being useful without a long learning curve.

The documentation provided with Qt and the example applications made it very easy for an experienced developer but Qt beginner to get up and running very quickly. I had UI prototype/mockups of the end application done by the end of my trial period. With Java/Eclipse, Java/SunStudio and C#/VS.net I had trouble getting anything nontrivial happening in that time.

Signals/slots took some getting used to, but it wasn't too bad, and I wrote some simple wrappers to assert when connections failed to stop silly typos from stopping the app. from working.

The other thing I liked is that Qt had almost everything I needed. You name it - storage, networking, GUI, threading, containers - Qt has a class to deal with it. Which IMHO is important because mixing libraries can sometimes cause problems.

Having the source code to Qt was a big plus, one for just plain interest's sake, but also it allowed me to compile Qt using the compiler and settings of my choosing, including a debug version for use during development.

I also found Trolltech's support to be fairly good. I raised a couple of bugs on Qt, one of which was fixed and released whilst I was still working on the project (only a 6 month job).

The only negative I can recall was the difficulty in debugging Qt objects (using VS) - there is a Qt plugin for VS that can examine Qt objects but I was using the free version of VS and plugins don't work for it. But that wasn't Qt's fault.

I haven't used jambi so can't comment.

Answer 7

Here are some of my Pros and Cons with Qt:

Pros:
Cross-platform
I know this one is always used, but after going back and forth between Windows and Linux with Qt, it's amazing how little I have to do to get up and running. I think this is helped by the fact I only use Vim with Qt Designer.

QMake
This is one of my favorite aspects of Qt. After doing work in wxWidgets, FLTK, etc., I get so tired of messing around with different build systems and I don't want to manually create my makefiles. I currently use CMake on anything other than Qt right now, but I think I'm slowly moving even Qt over to CMake. However it's just so easy to get going with QMake.

QTestLib
I looked at a couple other C++ unit testing frameworks and when I created my tests using QTestLib, it felt very similar to NUnit(C#) and within minutes I had several passing tests. I also noticed that it would be very easy to create my own continuous integration environment.

Closest to Java and .Net in productivity
The biggest thing I hear/read people say about C++ is, "I can be more productive with Java or .Net". From personal experience I can get a prototype of an application running in Qt using Vim and Qt Designer, before Eclipse or Visual Studio even load. I also get a very similar set of libraries in Qt that I have in .Net or Java and if it's not there I can leverage the existing C++ code out there.


Cons:
Price
This is the biggest factor I can think of right now. However, the cost is worth every cent, um if I knew how many cents I had to save up without making a call to a sales rep. I purchased a license back in the day when they had their small business discount and it was worth it then, I would've paid three times as much and I think that's the current price.

Develop anywhere with commercial license
I would love to be able to develop on any platform, but build and sell for another platform. For example, develop on Linux, then build and deploy on Windows if you just have the Windows commercial license. From what I know, you can only develop and build a commercial application on the platform you have a license for.

Vendor lock-in
Well sort of, this is more of a personal con. I don't like being tied to a specific vendor because I get side tracked by the company direction and product direction. TrollTech was purchased by Nokia, is this good or bad I don't know, but a company that size can do evil things.


I think I'm done for now :). Oh, I haven't used Jambi but I'm really interested in doing a couple prototype projects to find out how easy it is to use a plugin developed in C++ with Jambi. Especially using Jambi as a web interface with C++ plugins.

To be honest I haven't read much on it, so it may be impossible or very easy.

Answer 8

Don't use it, however...

Pro: QT has an optional 3 phase layout, where as WX only allows for 2 currently (I believe they plan to do 3 phase, just have not worked it in yet).

One of the bigger problems with using layouts is static text and wrapping. WX asks how big is your min width/height and portions out the screen, QT has option to say how wide do you want, how high do you need to be if your X wide. This allows you to express the flow of a page much better.

Answer 9

To handle failing connects (and other Qt Messages), you can use a custom message handler:
http://doc.trolltech.com/4.5/qtglobal.html#qInstallMsgHandler