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Programming languages are platform independent, so why is it that we can't write a program that will run on both a PC and a Mac?
I want to develop a software and I'm on a mac, but I want it to run on a PC also, is it possible to develop such a software without having to require the user to download a special program that will make my program compatible with their computer?
The problem with this is that most software is dependent on the OS to handle some tasks. Yes, most programming languages are compatible with many platforms, but the OS provides a lot of support. When software uses the OS, it is sometimes called making a system call. If you want here is some more information.
Theoretically if you write your program in a 'high level language' it should be portable between two operating systems.
Practically however, the differences start from the very beginning - the API of choice, which works on one and does not on another(Such as, Mac's BSD API is incompatible with Win32 API) and boils down to the very last, which is, executable format, linker and loader. Each operating system has its own quirks.
Then comes the difference between the underlying architecture. Previously Macs ran on PowerPC architecture and Motorola architectures, while PCs used Intel. Since Macs have switched to Intel, there have been attempts at making cross platform executables inside Apple. Most attempts have failed.
There is however a way around your problem. You can use a very high level language such as Python to code and then distribute your python code to your PC friends.(But remember remember, you need a Python interpreter in your PC friends' computers for your program to run). I have successfully ported Python programs from Mac to PC with 0 code changes, and sometimes requiring only 2-4% code changes.
Simple answer: because language per se is not enough to make an application cross-platform. Also the framework it uses must be cross-platform too, frameworks are required for everything: handling data, displaying things, communicate with the hardware, multi threading, etc
This can usually be done:
by choosing a complete solution like Java, which will actually run on both platforms seamlessly and even with the same binary
by using C/C++ and cross platform libraries so that the same program can be compiled for both platforms (keep in mind that you can't distribute the real same binary, you need to compile two in any case)
by writing the logic of your program just using standard libraries and a standard language and then attach whatever you need for a specific platform just to build two different libraries. Of course you will have to wrap as much as you need so that the cross-platform part of your program doesn't know it
Mind that developing cross-platform applications which are not trivial examples like a game (for which there are plenty of cross-platform APIs) without using a complete solution like Java is not an easy task at all. Especially because most of the GUI you can build are strictly platform specific and relies on their own frameworks.
If you want an application to run "anywhere" your best option is a JIT type language which means that it compiles as it runs (Just In Time) for the platform that it's on. Really the language that stands out in my mind is Java (there's others and personally I don't like java). However, it's not quite that simple. For example a Window on a Mac computer has pieces and functions that a Window on a PC doesn't have and vice versa. And other operating systems don't even have windows or anything equivilant yet still run Java like Android or iOS for example or countless Linux Distros. And that's just a very basic example it gets MUCH MUCH harrier. Really the best way to build an application that can be used by anyone on just about any device is going web based.
The lesson is that if it was that simple a lot of people wouldn't have jobs and it never will be that simple, things will always progress and change and not everyone is going to want to do the same thing with their OS as someone else. There's a million ways to skin a cat and there's many more ways to implement something in an OS.
Yes, it is possible. But it is quite tricky. You need to:
Use a cross platform language (this is the easy part, many languages run on different plaftforms)
Avoid using any platform-specific features (usually not too hard, but needs testing)
Ensure you have cross platform libraries for all your dependencies (hard!)
Because of the library issue in particular, there are very few options that work across platforms. Your best options are probably:
A JVM language (like Java, Scala or Clojure) - because the JVM abstracts away from platform specific features, pure Java applications and libraries will run on any platform. Java probably has the best ecosystem of cross platform libraries and tools as a result.
JavaScript - quite a good option if you don't mind running in a browser. There are lots of quirks to deal with, but JavaScript is one of the best cross-platform options because of it's ubiquity.
I want to write something like DaemonTools: a software that presents itself to the system as a real device (a DVD-ROM in the previous example) but it reads the data from a file instead. My requirement is not limited to DVD-ROM. The first goal is a joystick/gamepad for Windows.
I'm a web developer, so I don't know from where I could start such a project. I believe it will have to be written in C/C++, but other than that, I have no clue where to start.
Did anyone tried something like this and can give me some starting tips ?
Most drivers are written in either C or C++, so if you don't know those languages reasonably well, you'll want to get familiar with them before you start. Windows programming uses a lot of interesting shortcuts that might be confusing to a beginner - for example PVOIDs (typedef void* PVOID) and LPVOIDs (typedef void* far LPVOD;). You'll need to be happy with pointers as concepts as well as structures because you'll be using a lot of them. I'd suggest writing a really straightforward win32 app as an exercise in getting to grips with the Windows style of doing C/C++.
Your next port of call then is to navigate the Windows Driver Kit - specifically, you'll need it to build drivers for Windows. At this stage my ability to advise really depends on what you're doing and the hardware you have available etc, or whether or not you're really using hardware. You'll need to know how to drive your hardware and from there you'll need to choose an appropriate way of writing a driver - there are several different types of driver depending on what you need to achieve and it might be you can plug into one of these.
The windows driver kit contains quite a large number of samples, including a driver that implements a virtual toaster. These should provide you with starting points.
I strongly suggest you do the testing of this in a virtual machine. If your driver successfully builds, but causes a runtime error, the result could well crash windows entirely if you're in kernel-mode. You will therefore save yourself some pain by being able to revert the virtual machine if you damage it, as well as not having to wait on your system restarting. It'll also make debugging easier as virtual serial cables can be used.
This is quite a big undertaking, so before you start, I'd research Windows development more thoroughly - check you can't do it using the Windows APIs first, then have a look at the user-mode driver framework, then finally and only if you need to, look at the kernel level stuff.
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I'm trying to find a programming language I feel really comfortable learning and using for desktop/GUI application development. I realize it's unlikely that any language meets ALL of these criteria, but I'd like to find one that meets as many as possible. I've listed the following features ROUGHLY in order from most desirable/important to least.
Ideal Language Features:
Code Style: C/Java-like
GUI Development: Easy, elegant, and platform-Native styling
Community: Widely documented, active development, friendly & helpful, unity of focus
Object-oriented
Garbage Collection, no worrying about pointers, etc
Native compilation, NO 3rd-party runtimes like GTK or .NET
Multi-platform (can be compiled on *nix, Windows, Mac)
Reasonably fast
Mixed typing (soft-typed, OR both soft- and strict-typed -- i.e. Pike)
Background:
Most importantly, I need something that is straight foward and reasonably familiar, and something that isn't going to require a deep understanding of platform-specific APIs. I can't afford to spend a lot of time learning to develop Win32 apps in C++ for example. I've used wxWidgets, and liked the basic usage, but I'm really wanting to use a language with garbage collection, dynamic typing, and so on.
My frustration with Java, C#, and others is the need for a 3rd party runtime. I don't want end users to have to worry about installing and maintaining a separate platform.
Now then. Ideas??
Haha, due to the constraints you imposed you are now left with HTML and javascript. Good luck :)
The answer to your question is simply: None.
You excluded all desirable languages and platforms in your question.
I'd suggest you throw away your aversion against .NET and go with Delphi Prism. It's not C#, it is cross-platform compatible (everything is officially supported on Mono) and you can create applications that bring the runtime with them (Mono as part of your application).
I'd suggest Groovy and Griffon. Groovy is a dynamic language (like Ruby / Python) that runs on the JVM and integrates with millions of Java libraries out there easily. Griffon is a high-productivity RAILS-like framework for developing GUIs. Groovy has been around for 5 years and has a robust community and is supported by SpringSource (now division of VMWare). Griffon is a bit younger, but also has a fairly robust community.
These seem to fit your criteria.
I know I switched from Java to Grails (web framework written in Groovy that's similar to Rails), and haven't looked back.
Have you looked at QT? It's a really great GUI library and there are bindings for just about every language in common usage. There is a ton of documentation and a wide community. You mention that you want to do something in a language with garbage collection and dynamic typing, but rule out Python and Ruby, which are the 2 most popular languages that fit this criteria (also, they both have great QT bindings, I use pyQT4 and it is just awesome). They really aren't that far from what you do in Java/C, you just end up writing a lot less.
Wow you really limit your choices. I'm going to jump on the QT bandwagon and recommend C++.
Most of the objects in QT inherit from another object that sort of does it's own garbage collection.
There is incredible documentation out there for it.
QT is extremely powerful and has most of the elements you would like, and is extensible if you want to modify elements yourself.
If you do a static build for your release build the people you give the application to won't need distribute any other libraries as they will all be built into the .exe file.
The next iteration of Delphi is said to be cross-platform (Windows, Mac, Linux). I think it meets all your requirements except garbage collection.
No language meets all of those restrictions. Technically, it sounds like you're asking for something almost identical to Java but then explicitly disallow Java for unstated reasons. Conceptually, it sounds like you're looking for Python or Ruby but disallow them for using slightly different syntax.
Given the order of priorities, I think the closest you'll find in existing languages might be C with the Boehm GC and GTK+ for the GUI (and GLib for the object system). You do say "No GTK" under "No third-party runtime required", but I'm not sure what "runtime" you refer to here, since IIRC it's just a bunch of C libraries.
Given the specificity of the requirements, I think your best bet is to write your own language. Compilers really aren't that hard to write anymore. There are off-the-shelf tools to help with parsing and code generation and math and text processing and GC and so on. Once you get started you'll probably find people willing to help port it. Many existing cross-platform GUI libraries (like wxWidgets) use C/C++ so if you have a decent FFI you can use that, too. You want "support" and "documented" but if you're the primary author you'll understand it better than anybody. The hardest part about a language is design, and it sounds like you have a picture in your head of exactly what the language should be already.
There are a few if you can accept either WxWindows or GTK or QT as a toolkit.
In the order of my personal preference would be:
Eiffel Studio
D with the D-GTK binding
F#
javascript?
might be not the fastest one and doesn't fully address all your needs, but hey... its everywhere and easy to learn
didn't read after the list, but with prism You can probably achieve most your goals.
or You can try Qt and c++ autopointers
Silverlight could actually give you enough cross-platform availability to use C#/.NET, but I am not sure it fits all your requirements.
Sounds like Action Script 3 will make you happy. But it's more web oriented but you could try to make a projector or an Air application. I think it's a good solution because you can do anything with AS3 (image, video, text, sound video text keyboard and mouse input, pear to pear and 3d since flash 10, ...) and it's cross platform and you can use it on the web or your desktop :)
If you are a pure root coder (using vim and only command line for ex) you can make your whole app without using the flash ide, by just writing your as files and compiling them with mxmlc (that comes with the free flex sdk).
I suggest Python. Although it doesn't fit your first requirement of coding style, but it fits all your other requirements!
GUI Development: Easy, elegant, and platform-Native styling --> Yes
I'd suggest that you try wxPython (wxWidgets for Python). This is so "native" on Python that about 90% of all the wxWidgets code examples on the Internet are for Python! I've personally used TkInter, Gtk and wxPython. All of them are well supported on Python. My personal choice is wx.
Community: Widely documented, active development, friendly & helpful, unity of focus --> YES
Object-oriented --> Yes
Garbage Collection, no worrying about pointers, etc --> Yes
Native compilation, NO 3rd-party runtimes like GTK or .NET --> Yes. - You can eiter:
pack a single dll with your code - or
use py2exe which is able to create a single executable out of your project
Multi-platform (can be compiled on *nix, Windows, Mac) --> Yes.
Reasonably fast --> Yes. Well, it's not the fastest out there, but close enough that some serious projects are done in Python only.
Mixed typing (soft-typed, OR both soft- and strict-typed -- i.e. Pike) --> Yes.
Regarding your first requirement I'd say that you should give Python at least a try. It requires very little effort to get started. There is a 2-hour tutorial which gives you a serious introduction. There's a Basic to Advanced tutorial where I'd almost guarantee that you'll be writing your first application on the second day.
I also feel your pain Brian. Most time when I ask questions about desktop GUIs the only answer I get is: "Make it Web". You really nailed it, since your question is still open inspite some really non-constructive answers...
I've been watching closely JavaFX 2, it solves some of Swing problems and seems very promising. This may be the only thing Oracle did right since getting Java from Sun.
UPDATE:
.NET is finally becoming an open-source, cross-platform solution. .NET Core allows native compilation for multiple devices.
The new .NET experience is exactly what I was looking for when I asked this question several years ago.
Original:
Lots of good suggestions, despite being salted with negativity throughout.
I think I'm going to go with C# and Mono. I like C# well enough syntactically (I've been accused often of being shallow, but the syntax of a language is just as important to me as its features, because I spend a lot of time writing in that particular syntax). Although similar to Java, it has a few unique features that I appreciate, and I think the community seems more open-minded.
My biggest complaint about Java besides performance, frankly, is the community. It seems infected with an excess of arrogance, and it also seems to be very fragmented in terms of support for and development on various overlapping libraries, tools, and so on. The community surrounding Mono seems much more organized.
Actually, so does .NET itself, for that matter. Sun is a big enterprise company that seems every bit as confused about what it IS and what it DOES as Microsoft or IBM, yet they seem to be doing an even worse job of leading and organizing their platform than Microsoft, which is pretty tragic.
Ok, this is an interesting question to ask because everyone has a say in it.
What is your favorite library to program in for GUI's and the language that you program it in. Give a short reason why. (ex. Gtk, Qt, Windows, etc..) Just an FYI, this includes any scripting language that you program a GUI in Python, Perl etc...
Frankly I've always done Gtk in C, but I'm starting to warm up to Qt in C++ with the new KDE. I've never been a big fan of Windows programming.
ChrisW. stated that I did not give a reason for Gtk/Qt so here goes. I started with Gtk because when I started programming GUI's I was working in Linux and there was more Gtk information available. Started utilizing Qt when I started working more in KDE but really the move to Qt was based on trying to move to C++ and learn more languages. I've never been a fan of basic Windows programming, but I do enjoy a little DirectX now and then :P
Recently I had the opportunity to work with both wxWindows and QT, while some time ago I wrote some small programs using FLTK and Gtk. My conclusion is that widget libraries tend to be very similar; each one has its strenghts and its quirks.
Instead of advocating a specific library, then, I would like to advocate the use of high level languages in GUI programming: the development cycle is way faster and GUI programs are rarely CPU bound, so the performance hit is rarely a problem.
If a GUI program has to perform some intense computations, just develop a core library in C or C++, but keep the interface in Python or whatever other interpreted language.
People like to bash Swing for being old, slow and ugly, but it's just not true. Swing is mature, is faster than ever on Java SE 6/10, looks decent enough, and is tolerable to program. Above all, I've found Java + Swing to be the most trouble-free cross-platform combination. It also works remarkably seamlessly with Jython (Python on JVM).
SWT could also be an option, but so far I've been happy with Swing.
I realise you're focusing on application GUIs but if you want a quick, powerful and fun way to visualize anything on your computer, you can't go past Processing
From the site:
Processing is an open source
programming language and environment
for people who want to program images,
animation, and interactions. It is
used by students, artists, designers,
researchers, and hobbyists for
learning, prototyping, and production.
It is created to teach fundamentals of
computer programming within a visual
context and to serve as a software
sketchbook and professional production
tool. Processing is an alternative to
proprietary software tools in the same
domain.
WPF in particular, and XAML in all its reincarnations (WPF, Silverlight, Moonlight).
C# on top of .Net 3.5/Mono: $0
Visual Studio Express/MonoDevelop: $0
Being able to tell the designer "make my program pretty" and continue coding features: priceless.
I liked writing to video memory under DOS: for an animated game (i.e. an Asteroids clone), that was as fast (performant) as I knew how to do it (certainly faster that using the BIOS API).
This is really a somewhat subjective question, so there is no best or correct answer to it. The following is based on my (limited) experience:
I personally like wxWidgets with PLT Scheme for writing simple but flexible GUIs. There are much more advanced toolkits, but I usually do not need their features. wxWidgets is flexible and the Scheme interface follows Scheme traditions of being powerful with a relatively simple structure. I like the fact that wxWidgets is portable, and yet tries not to actually draw its own widgets, but can use native or common toolkits of the environment it is used under. It is written in C++ but I never used its C++ interface.
That is not to say that in my opinion Scheme will generally be the optimal language to write your application in. In fact there are many kinds of applications I would not write in Scheme, even though I like the language. But regarding the GUI programming part, that is my favourite because of its straight-forwardness, and the way that a functional language like Scheme goes well with declarative-style GUI programming.
Of course you will not have the same level of control when using that as when having your program involved in every stage of the window construction and input reaction, by using an event loop (such as with Win32API or Xt/Intrinsics). But that is not always convenient and often unnecessary, and seems to become decreasingly common.
Note: The wxWindows toolkit was renamed wxWidgets, but my installation of a rather recent version of PLT Scheme still comes with the older wxWindows. I am not sure whether there is an updated package of wxWidgets available or if it is going to be included in a future version of PLT Scheme.
Qt4 without question for me. Now that it has an LGPL license it makes sense for all kinds of applications that previously weren't possible. Additionally, it changes C++ in ways that dramatically improve the experience of using the language. (Things like a foreach and forever loop, atomic operations on integers, and memory management)
Gtk and is the primary window-drawing graphical subsystem I have experience working with (and is therefore my favorite XD).
As far as general graphics subsystems go, however, OpenGL (typically in combination with GLUT) has been an easy and productive ride for me. Regrettably I have little DirectX experience to compare to, though :S
For writing souped-up versions of standard Windows components, I loved Borland's VCL, and am very pleased with .NET.
my background: i've been developing web applications using php and javascript for the past ten years. before that, i've developed applications using turbo pascal for DOS. in my opinion application and web application development are two different kinds of development (at least it's what i think when i remember back the old days of DOS application development).
now i am in the need to go back to "normal" application development for various reasons. the application i want to build needs a GUI and it has to run on osx and windows. as mac os user it would be very nice for me to get an application as result, that really feels like an osx application. i don't need any special UI components: an explorer/finder like tree, a datagrid and some form-elements would be enough for my needs.
now the problem is, that i don't know where to start: i would classify me as newbie, because it's that long time since i last developed anything other than a web application. are there any recommendations of programming languages and gui toolkits with a not to steep learning curve? or can you recommend any book i should read for getting into cross-plattform osx/windows app development?
many thanks!
thanks everyone! i think i'll have a look at realbasic!
Edit Nov 2011 - a retraction
Most of what I say below is still true however I have now got serious reservations about recommending REALbasic for anyone trying to release commercial-quality applications. To save me remembering to edit this post later, see if RealSoftware have managed to release a robust version of their IDE using the Cocoa version of their frameworks. If not, be very cautious.
It's with a heavy heart that I write this because I still really like the language and think the framework and IDE are well-done. The problem is apparently one of under-capitalization and possibly a software development culture inside the company that consistently fails to deal with a bug regression problem. Many bugs are fixed each release but there appears to be a huge tax on the developers in the number of introduced bugs. They have a very small team for the complexity of the product, especially considering the newly released Web Edition which is effectively an entirely new platform.
It's still theoretically a great product but take advantage of the trial period, test it thoroughly on each of the platforms you plan to target and decide if you can live with any bugs you find because they may be there for a while.
REALbasic.
The language is a powerful, modern OO language that won't be hard for you to adapt to from your vaguely remembered Pascal or current JavaScript. It has most of the power of C++ without the dangerous bits that make debugging a nightmare. You will also find the IDE simpler and easier to deal with than say Visual Studio.
The IDE makes it very easy to throw together a GUI and have it just work on multiple platforms. The Pro version has one of the best cross-platform debuggers I've used and it is easy to just work (say) on a Mac and develop for Windows and Linux, compiling and testing with one click.
There is also a thriving community including many people at your level of expertise so you won't be mocked for being a newbie.
I am a professional software developer with over 25 years experience and currently mainly working in REALbasic, C++, C#, Objective-C and a bit of Ruby. For apps such as you mention, REALbasic is my tool of choice.
edit: I can't believe someone downvoted this but didn't have the guts to add a comment explaining why. I'd heard about prejudice against REALbasic but this is the first time I've encountered it. In what way was my answer inappropriate for this question?
Just to add to my cred, I've implemented cross-platform frameworks used by systems deployed to tens of thousands of end users - I have the C++ cross-platform experience to applaud someone else doing a good job and the REALbasic frameworks are very nice.
The best cross-platform tool I've dabbled in with a relatively small learning curve...especially if you're familiar with Visual Basic...is REALbasic. With REALbasic Pro you can compile a program to target Win32, Linux, and OS X from the same codebase, as long as you're not using OS-specific calls and features (which you can do with plugins or direct calls). Their support has been pretty responsive to my questions, the personal edition (which compiles to only the single target platform you'd downloaded the IDE for) is free for Linux and inexpensive for other platforms, but really you might want to download and try it out. One IDE, relatively inexpensive, and can compile native applications on OS X, Windows, and Linux...it's less hassle, and for me that's important when you want to get a job done.
I'd advise against C and Qt and would also recommend REALbasic.
With your background in Pascal and probably JavaScript you'll feel much more comfortable with REALbasic. I've done a lot of coding in Pascal and C/C++ - where Pascal guides you to avoid programming mistakes, C lets you step right in, even invites you, and then you'll have a hard time figuring out why it went wrong. Qt is a very abstract framework and requires you to learn a lot before you can get something working, just like with C. When compared to the easyness we used to have with TP back then.
RB is much more like Pascal in this regard. And its IDE is quite modern in regards to supporting your programming, with an easy-to-use GUI designer, straight-forward editor to fill in the gaps for handling UI events, code completion, etc.
Only when you get into huge program sizes, RB loses some of its appeal because it is missing tools to give you a good overview of complex class interactions etc.
Another thing is that Qt is more likely to cause ugly-looking Mac apps than RB would. RB visually guides you to get it all aligned nicely - in Qt you have to work with numbers, offsets, etc. to position your objects (at least it was that way when I used Qt 2 years ago).
I've written quite a few x-platform apps in RB and am pretty happy with the results.
You won't probably write those super-nice looking apps that compete with the best on the open small business market, but if you just want to get some solid code working, with an easy-to-design UI that's acceptable to the average user, give RB a try.
It's not free, though. But its rather small community is on your side - they're eager to help, instead of bashing everyone who's trying to talk sense :)
I'm new here but picked up on this thread through the REALbasic User Group. I think my position was similar to yours. I did website design for my work, using mostly javascript (with a little php, not much). I had a Pascal and BASIC background. I'd dabbled it C but didn't like the level of detail you needed to monitor it. It reminded me too much of assembly (which I still have nightmares about from my high-school/college days).
I was looking for a cross-platform language, with a familiar feel to it, but initially started with VB because it was free. I prefer programming in MacOS however, so I tried REALbasic. I found that REALbasic's UI builder was much easier to use than VB's. I'd echo other comments that the community is the most responsive of any user groups I've been involved with. I've since used REALbasic and my Mac to make several programs that over 100 users use every day at my work (on PCs, mostly XP and 2000). I've received compliments on the polish and ease of use of these programs. You DO have to remember to adjust the 'little' things to make it look right cross platform (ie: default button placement is opposite on PC vs. Mac, button sizes are different on Linux, etc). Many people have donated custom classes that do this stuff for you though.
People seem to assume that a "BASIC" language cannot be powerful enough for their purposes. While it is BASIC at it's core (with For..Next, Do..While, and If..Then commands), it ain't your daddy's BASIC. It's much more OOP than anything else I've used, based upon an event-driven structure, which for me was easy to pick up. They have a free trial, so grab a demo and run through the tutorial. If you get stuck, ask for questions on the NUG or Forums at the website and you'll likely get an answer quickly.
You may be interested in the following questions and answers:
Cross-platform development - Go with a cross-platform UI toolkit or native on multiple platforms?
Easiest cross platform widget toolkit?
Should I use a cross-platform GUI-toolkit or rely on the native ones?
Using a Mac for cross platform development?
and many others suggested in the Related sidebar of these questions.
Some answers suggest gtk (which is used by cross-platform gimp). Others suggest native approaches. Some suggest that a Mac is a nice platform for developing for Mac OS X, Windows, Unix and Linux.
I wholeheartedly recommend RealBasic too. I have been using RB for about 8 years now and find it to be a perfect tool for my Companies development needs, from small apps, to large multi-user systems.
It is perfect for beginners and those that are getting back into programming, and also for professional developers.
Highly recommended.
As Andy Dent and others here have indicated, for a newbie to create cross-platform applications it is hard to beat REALbasic (now Xojo).
Sure, there are plenty of other cross platform solutions such as QT (C++), Java, .NET (to some extent) and wxWidgets but they are not something a beginner would be able to use effectively.
I have many years of professional development experience in a wide variety of languages and technologies and I prefer to use REALbasic most of the time.
With that said, you might also consider Runtime Revolution or Adobe Air.
Whilst it might seem tempting to use a language thats platform independent and allow you to write the app once and use anywhere, you will undoubtably be sacrificing something on each, particularly in the UI and user experience.
If you can your best creating something using a native API that lets you take full advantage of the features of the OS to make your application shine.
I would definitely go for C++ and Qt, the code you write once will compile and run without problems on Windows, Mac and Linux. The new IDE that comes with Qt - Qt Creator is brilliant, works and looks the same on Windows, Mac and Linux, you don't need to anything else to start writing cross-platform applications.
I tried WxWidgets but didn't find good IDE, the best one was Code Blocks but GUI Designer is not perfect and has different problems on different systems and the IDE itself is still under heavy development.
Other options are Java and C# but those are not cross-platform languages, those are platforms themselves. Although you wouldn't need to compile code for each platform there will a lot of different issues on the way...
If your GUI's simple enough, why not just create a generic GUI layer, then program to that? Compile a version for each OS using native widgets. That's the best way to ensure native L&F on multiple platforms.
Both the Qt and REALbasic suggestions are good, although they tie you to that particular technology (which I can't imagine would be an issue in this particular case).
Personally, I'd go with Java, because it's worked for me before (I had an app that ran on my PDA, my phone and my desktop), but it doesn't use native widgets.
Adding a late comment here:
Take a look at Revolution. It's sort of like a modern Hyper-card on roids. And it's cross platform (Mac, Linux and Windows). This is a serious competitor to RealBasic and is coming on strong. Though I still use RB (and like it) I'm giving Revolution a serious look at.
I would also look into either Realbasic or Revolution. They both create cross platform native apps. Personally I think Realbasic would be a better choice as it is very similar, language wise, to VB. You can learn some valuable skills with RB and it can grow with your experience. I have been using VB and RB for more then 10 years combined and I think you will be happy.
If you need your code to be cross platform, you would have to go with something like QT.
Although, I would recommend using native API for each one (Cocoa for Mac OS X, .NET or the Win32 API for Windows). User experience will be much better. But of course, that will cost you more money in terms of developers hours.