Cross-platform development solutions for (mobile) performance computing - performance

I am looking for a programming language/platform which is suited for handling around 1 to 2 GB of data, and can run signal processing algorithms fast enough across platforms (including modern mobile platforms). Did someone come across suitable solutions?. Please share your research and experience on cross-platform development.
My current research effort is complicated, owing to
the increased deployment of powerful [mobile] platforms,
the backing of Java through the popularity of Android (currently the #1 tag on stackoverflow)
I had mixed experience with C# and Mono (It is fast, but cross-platform compatibility can take some additional effort).
I am not looking for High performance computing(HPC), but into developing code with a data and computing-intensive background that performs well with as little effort as possible. A case study scenario for this would be Python code which is adapted to the Cython compiler.
I am not looking for UI-centric projects with solutions such as Phonegap and Adobe Air, but I know little about its performance.
Links:
Cross-Platform Development of High Performance Applications
Using Generic Programming
Native Client: A Sandbox for Portable, Untrusted x86 Native Code

You can perhaps start having a look at Droidcluster

Related

Performance of Node-Webkit Desktop Applications

I need to create a desktop-application that has to handle some animations and a bunch of logic.
I thought about creating it with node-webkit which I never have used before.
Is anybody here who already wrote some desktop-apps and experienced the performance compared to something coded in c++?
So there's 2 parts to this question:
1) Speed comparison of Javascript executing under V8 (node-webkit), vs C++ compiled into native code
On most computationally-intensive tasks, you'd expect a 3x to 10x slowdown in execution (depending on the benchmark). An example can be found at http://benchmarksgame.alioth.debian.org/u64/benchmark.php?test=all&lang=v8&lang2=gpp ; if you want more examples search for other v8 benchmarks.
2) Speed comparison of browser-based UI toolkits (based on the DOM and CSS, and perhaps WebGL) as rendered with Chrome's engine, vs whatever desktop UI toolkit (for example, Qt, WxWidgets, etc) and/or 3D-rendering API (DirectX, OpenGL, or various different wrappers around them) that you'd be using with C++.
This unfortunately is rather difficult to benchmark, as there are tons of different UI toolkits out there, each with differing performance characteristics for each type of animation / widget that you might use (depending on how they were implemented). If you're 3D rendering and want to compare Javascript+WebGL on Chrome to C++ with DirectX, see https://www.scirra.com/blog/58/html5-2d-gaming-performance-analysis for an example benchmark (their figures indicate a ~5x slowdown); if you want more examples search for performance benchmarks comparing WebGL to OpenGL and DirectX.
Generally speaking, well-implemented C++ should execute faster than Javascript running under node-webkit, simply because there's fewer layers of abstraction away from the hardware. That said, unless you're building an exceptionally computationally intensive application, the difference will likely not be visible on a modern desktop, and you should be focusing more on ease-of-development rather than performance.
Using node-webkit also gives you advantage of the countless UI libraries built for browsers, which will likely accelerate your development time, especially if you already have experience in frontend web app development. There are also advantages in terms of portability - unless you use a cross-platform UI tookit like Qt with C++, you will need platform-specific UI code, whereas with node-webkit you get cross-platform portability for free.

Prototyping and simulating embedded software on Windows

I am looking for tools and techniques for prototyping (virtual prototyping), simulation, and testing of deeply embedded C code on desktop Windows, including building realistic embedded front panels consisting of buttons, LEDs, and LCD displays (both segmented and graphic).
I'm specifically interested in a possibly low-level approach, using pure C code and raw Win32 API rather than MFC, .NET/C#, vxWidgets or Qt. I'd also like to use free development tools, such as Visual C++ Express with Platform SDK and ResEdit for editing resources.
I'm looking for code examples to render graphic LCDs (from monochrome to 24-bit color) with efficient pixel-level interface, multi-segment LCDs, and owner-drawn buttons that respond both to "depressed" and "released" events.
I am surprised that my original question triggered so many misunderstandings and adverse comments. The strategy of developing deeply embedded C code on one machine (e.g., a PC) and running it on another (the embedded microcontroller) is called "dual targeting" and is really quite common. For example, developing and testing deeply embedded code on the PC is the cornerstone of the recent book "Test-Driven Development for Embedded C" by James Grenning.
Avoiding Target Hardware Bottleneck with Dual Targeting
Please note that dual targeting does not mean that the embedded device has anything to do with the PC. Neither it means that the simulation must be cycle-exact with the embedded target CPU.
Dual targeting simply means that from day one, your embedded code (typically in C) is designed to run on at least two platforms: the final target hardware and your PC. All you really need for this is two C compilers: one for the PC and another for the embedded device.
However, the dual targeting strategy does require a specific way of designing the embedded software such that any target hardware dependencies are handled through a well-defined interface often called the Board Support Package (BSP). This interface has at least two implementations: one for the actual target and one for the PC, for example running Windows. With such interface in place, the bulk of the embedded code can remain completely unaware which BSP implementation it is linked to and so it can be developed quickly on the PC, but can also run on the target hardware without any changes.
While some embedded programmers can view dual targeting as a self-inflicted burden, the more experienced developers generally agree that paying attention to the boundaries between software and hardware is actually beneficial, because it results in more modular, more portable, and more maintainable software with much longer useful lifetime. The investment in dual targeting has also an immediate payback in the vastly accelerated compile-run-debug cycle, which is much faster and more productive on the powerful PC compared to much slower, recourse-constrained deeply embedded target with limited visibility into the running code.
Front Panel Win32 GUI Toolkit
When developing embedded code for devices with non-trivial user interfaces, one often runs into the problem of representing the embedded front panels as GUI elements on the PC. The problem is so common, that I'm really surprised that nobody here could recommend an existing library or an open source project, which would provide a simple C-only interface to the basic elements, such as LCDs, buttons, and LEDs. This is really not that complicated, yet it seems that every embedded developer has to re-invent this wheel over and over again.
So, to help embedded developers interested in prototyping embedded devices on Windows, I have created a "Front Panel Win32 GUI Toolkit" and have posted it online under the GPL open source license (see http://www.state-machine.com/win32). This toolkit relies only on the raw Win32 API in C and currently provides the following elements:
Dot-matrix display for an efficient, pixel-addressable displays such as graphical LCDs, OLEDs, etc. with up to 24-bit color
Segment display for segmented display such as segment LCDs, and segment LEDs with generic, custom bitmaps for the segments.
Owner-drawn buttons with custom “depressed” and “released” bitmaps and capable of generating separate events when depressed and when released.
The toolkit comes with an example and an App Note (see http://www.state-machine.com/win32/AN_Win32-GUI.pdf), showing how to handle input from the owner-drawn buttons, regular buttons, keyboard, and the mouse. You can also view an animated demo at http://www.state-machine.com/win32/front_panel.html.
Regarding the size and complexity of the "Front Panel Win32 GUI Toolkit", the implementation of the aforementioned GUI elements takes only about 250 lines of C. The example with all sources of input and a lot of comments amounts to some 300 lines of C. The toolkit has been tested with the free Visual C++ Express 2010 (with the Express Edition Platform SDK) and the free ResEdit resource editor.
Enjoy!
The appliances you mention in your comment clarification to the question will never be using a windows PC, so low level windows programming is not a requirement in that case. In fact, I'd say its undesirable. Prototyping is about speed. It's about how fast you can put something together to show potential investors or upper management or some other decision maker.
You wouldn't want to spend the extra time with low level C and Win32 api until the project requirements were flushed out enough that you knew that was an absolute requirement for the final project deliverables (perhaps a server/PC monitoring tool?). Until then you want speed of development. Lucky for you the industry has tools for rapid prototyping and development of hardware like you describe.
My Preference for Prototyping with Embedded Development
As for my opinion as a developer, I like the .net microframework (.netmf) simply because I'm already a Microsoft .Net developer and can transfer a lot of my existing skills. Therefor I prototype with a FEZ microcontroller using C# under Visual C# Express 2010 (free as you required). Its fast, easy and you are working on the core of your project in minutes.
If your experience as a developer is different, you may look for a micro controller which is programmed using BASIC, Java or some other language to help with the speed of development by reusing your core skill set.
Addressing your Question Bounty Comments
Astonishingly large portions of the embedded software can be developed
on the desktop computer as opposed on the deeply embedded target. This
avoidance of the "target system bottleneck" can potentially improve
productivity by an order of magnitude, if done right. However, to
develop embedded software on the desktop, one needs to simulate the UI
components, such as displays (both segmented and increasingly
graphical), LEDs, knobs, and buttons. I'm looking for such UI
components written in plain Win32 API in C for easy integration with
embedded code to be developed and tested on the desktop Windows.
I did embedded development full time professionally for well over 4 years as well as many years surrounding that part time. While what you said above is somewhat true, it will not save you time or money which is why everyone is confused about the motivation for this strategy. We spent years trying to put out a windows emulator for this company's hardware devices that would theoretically save time for prototyping. It was always a pain and we spent many more hours of work trying to emulate the experience than if we just went straight from sketched UI drawing specs to real development. The emulator lagged behind hardware development and often wouldn't support the latest features until 6 months or more after the hardware was released. It was a lot of extra work for very little value.
You will spend more of your time developing non-reusable win32 platform code and hardware emulation components than actually writing the code for the core project itself. This only ever makes sense for hardware vendors who provide this emulator as a 'value add' tool to potential 3rd party developers, but it does not make sense for prototyping new hardware designs.
Modern development environments like Visual C# Express 2010 with a FEZ microcontroller can compile, push the project output to the microcontroller, and then begin debugging just as fast or faster than you could compile and run a low level windows app in C emulating LCDs or LEDs or switches, etc... So your comment, "improve productivity by an order of magnitude", is simply no longer true with modern tools. (It may have been prior to the last 10 years or so.)
If you really, truly just want to simulate the embedded hardware visually on a PC use something like adobe flash to mock up a UI. But don't duplicate code by coding for windows when the final device you are prototyping won't be running windows (maybe it will be, but you didn't say that). Use the fastest most reliable prototyping tools available today, which is unequivocally not low level C and win32 api!
Maybe use StackExchange for Electronics?
Because this is a development oriented site, discussion about the merits of specific embedded hardware isn't really relevant. If you decide to refocus on using microcontroller electronics for prototyping (Arduino, FEZ, Propeller, Basic Stamp, Pololu, etc) you might ask for electronics hardware advice on stackexchange for electronics. I will say that most of those platforms are designed to facilitate the prototyping of LCDs, LEDs, buttons and interfaces as you outlined. You can usually assemble a few pre-built modules in a matter of minutes and be ready to start coding your project. Huge time savings can be had here.
You are asking for too much you need to take a look # proteus.
http://www.labcenter.com/products/vsm_overview.cfm
As Mahmoud said, you may find your code solution with prototyping example in proteus professional. It is one of popular software for prototyping, simulation and coding, you can download proteus professional for free and check their manual.
Best of luck

Comparing Qt4 with Cocoa

I'm on the beginning slope of learning Mac programming and in particular Cocoa. It seems to be a comprehensive framework providing all kinds of things every app programmer needs. Qt4 is the same sort of thing at a general level, except it runs on other platforms and uses C++ instead of Obj-C. More importantly for me, I've used Qt4 and so am familiar with it, though hardly expert. I am new to Obj-C and app programming in general, but know C++.
I'd be interested in comparisons of Qt4 and Cocoa, tips for those starting one coming from the other (either way), and discussions on their internals, API design, intended uses, how the designers of each made decisions about how things should work, etc.
What are some recommended readings?
(Of course, I want serious writings by professional developers with real experience with both, not flame wars or fanboy gush or marketing pablum.)
So far I have used Qt4 to implement some cross-platform applications (Windows & Mac) and I used XCode (Objective-C) only for iPhone Applications development - therefore I don't have first-hand experience in using Objective-C for native Mac applications.
I think the best advantage of Qt4 is portability, and I love it for it.
Not only you may port the entire Qt Application to different environments, but with a small effort you can create standard C++ libraries (libraries that not use Qt4 Classes) which are far more useful and portable.
On the other hand, I think the XCode/Objective-C environment is more mature regarding project management and UI Design and off-course you can use the full set of Mac-OS native calls in your application. As you may know Objective-C is fully compatible with C++ and you can use any third party C++ libraries, but if your main environment is XCode/Cocoa you will finally find yourself writing mainly Objective-C code which cannot be ported to any other environment but Mac-OS/iOS.
Therefore to cut a long story short, I think your decision must be based more on your long-term needs than to any environment/design/language/API details:
=> If you know that you will build Apps for Mac-OSX (or iOS) for the next 1-2 years and there is no portability requirements, go with the XCode/Objective-C approach to create a more solid base for Mac Application development.
=> If this is a "Just One Mac/OSX Application" thing and then you will return to Qt4 or another environment, maybe it's better to stick with Qt4, enjoy the advantages of portability and use the experience you already have to reduce the developing time.

Favorite graphical subsystem to program in

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.

osx & windows development -- for newbies

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.

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