Lazarus for Cross-Platform Development
Lazarus is an open-source library of visual components and a powerful IDE for rapid cross-platform development. The IDE contains all the features of a modern development suite, including a debugger, code completion, visual designers, refactoring tools, and translation and documentation tools. The Lazarus Project started on Linux ten years ago and now runs on all major platforms: Linux, Windows and Mac OS X. The Lazarus Project's motto is “Write once compile anywhere”, and it provides cross-platform libraries, a cross-platform compiler and a cross-platform IDE.
Lazarus' features include the following:
An easy-to-learn language: Pascal.
A visual form designer.
Producing native code executables that execute with speeds comparable to C/C++—no virtual machine here!
Allowing direct access to system libraries.
Supporting embedded assembler code.
Easily handling big projects with millions of lines.
Compatibility with the Delphi visual component library.
And, if all that weren't enough, Lazarus also is open source and free of charge, even for commercial development. The Lazarus IDE is shown in Figure 1.
Lazarus uses the powerful Free Pascal Compiler (FPC), which understands Object Pascal (a descendant of Pascal). Free Pascal (aka, FPK Pascal) is a 32- and 64-bit professional Object Pascal compiler. It is available for the following operating systems: Linux, FreeBSD, Mac OS X/Darwin, DOS, Win32, Win64, WinCE, OS/2, Netware (libc and classic) and MorphOS, and for different processors: Intel x86, AMD64/x86_64, PowerPC, PowerPC64, SPARC and ARM. You can find binaries, packages and daily snapshots at the Free Pascal and Lazarus Web sites (see Resources). Free Pascal creates native code executables, like C and C++, and uses the GNU tools and object format, so it can use C libraries directly, and, of course, C/C++ code can use FPC libraries. The speed and size of the created code is comparable to GCC.
FPC also compiles fast—normally more than 10,000 lines of code per second. That is because in Object Pascal, forward declarations are more limited than in C/C++. This saves a lot of time, even for small programs, and allows you to be more productive. After a while, you'll compile without thinking, just to highlight even obvious errors.
The Free Pascal Compiler itself is written entirely in Object Pascal. At the time of this writing, the compiler is at version 2.2.4.
FPC runs on more platforms than Lazarus. On those platforms, you can use the FP IDE, which runs in a terminal. The FP IDE usually is installed together with FPC and you can start it by typing fp.
Like its ancestor Pascal, Object Pascal is very easy to learn. C and Java programmers will understand most Pascal code without any tutorials. The language is very type-strict, and many code inconsistencies are spotted at compile time. This is especially useful for big projects, when a refactoring eventually is needed, and all affected places must be found. The compiler also warns when a statement works on the current platform but may fail on another—for example, when an expression works differently on 32- and 64-bit systems.
Lazarus gives FPC a face by providing the Lazarus Component Library (LCL), a library of visual components, such as buttons, edit fields, file dialogs and much more. These components run on Linux, MS Windows, Mac OS X, FreeBSD and Solaris using native widgets. Additionally, on Linux, you have the choice between GTK or Qt as a back end. The LCL calls the back-end widget sets and provides the glue between the platform-independent API and the widget set. The code itself needs to access only the LCL API, so no change is required when switching the widget set.
An LCL application compiled with GTK creates a native GTK application running on most Linux distributions out of the box. Under Windows, the choices are the WinAPI, GTK and Qt. For Windows CE, the back end is called wince. Under Mac OS X, the choices are Carbon, GTK and Qt. The widget set can be chosen automatically by the IDE or selected manually in the dialog for the compiler options. This allows you simply to copy a project developed under Linux to Windows and compile.
Some other LCL interfaces are under development—for example, fpgui, a widget set written completely in Object Pascal and Cocoa for the new Mac OS X libraries. So, if you don't care about native widgets and you want your application to look and feel exactly the same on all platforms, you can make use of the LCL and the fpgui library, which currently runs on MS Windows, MS Windows CE and Linux with X.
The Lazarus IDE uses the LCL and has an integrated visual form designer, which allows you to edit forms graphically, like Glade or Trolltech's Qt Designer. Lazarus' designer works directly with the corresponding Pascal unit source. For instance, double-clicking on a button in the designer automatically creates the OnClick in the source code and connects the button and the event handler. No further work is needed—simply compile and run. And, it works backward too. Remove a method from the code, and the IDE will disconnect it from the designed form.
The IDE even supports connecting two designed forms. That means a component on form1 can access the components on form2. No extra source code is required for this, just some mouse clicks.
The designer also allows you to inherit forms visually. For example, a base form can be created for all of an application's dialogs. Descendants can be created visually that inherit from this dialog. No extra source code is required. Even embedding a form into another form as a subcomponent can be done visually.
Of course, everything done in the designer can be done via source code at runtime too. The form data is stored in .lfm files, which are simple text files, so they are cross-platform also.
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