Gambas components are shared libraries written in C or C++ that add new functions to the Gambas interpreter.
They act like Linux drivers towards the Linux kernel:
A component can contain:
A component must have a name. This name is the the word gb
followed by a dot-separated list of words describing
the role of the component and another component it relies on, if any.
For example, gb.qt.kde
is a component that transforms a Gambas application into a KDE application. This component
relies on the gb.qt
component, i.e. loading the first implies loading the second.
The Gambas Programming Interface is a set of utilities, functions and macros that allows you to:
The use of this programming interface is highly recommended, as it prevents a component from doing weird things.
The Gambas Programming Interface is a C structure that contains one function pointer for each function of the interface.
This structure is declared in the main file of your component and is automatically initialized by the interpreter at component loading.
Writing good components is the difficult part! Let's suppose you want to write a SDL component, i.e. a component that lets a Gambas project use all the power of the SDL library: graphics, sound, CD-ROM...
You can be content with just wrapping the library functions, structure and constants. It is the easy way, even if wrapping C structures and functions may not be possible in every case with Gambas.
Your component will be useful, but not very interesting for the Gambas programmer, because he will be obliged to program in C or C++ style.
Instead, you should rack your brain to create a different interface between Gambas and the library, by trying to generalize and simplify the original interface of the library.
That is what I did with QT: it is far easier to use the QT component than programming the QT library directly. And if one day somebody writes a GTK+ component, he will be able to use the same interface because I tried to generalize the QT interface by avoiding all the QT specific stuff... Well, to be honest, I put all the useful QT specific stuff into a dedicated extended component, gb.qt.ext
The source files of a component are stored in a sub-directory of the lib
directory of the source package.
The path of this directory reflects the name of the component.
For example, the gb.qt.kde
component sources are stored in the ./src/lib/qt/kde
directory.
A typical component directory contains :
Makefile.am
file that describes how to compile the component. (new topic)
For example, here is the result of ls ./src/lib/qt/kde
just before the compilation :
CApplication.cpp CDatePicker.cpp CDialog.cpp lib.gb.qt.kde.component main.h Makefile.am CApplication.h CDatePicker.h CDialog.h main.cpp Makefile Makefile.in
The component source directory structure looks something like this:
-+- lib | +---+- db | | | +----- mysql | | | +----- postgresql | +----- eval | +----- example | +----- net | +---+- qt | | | +----- editor | | | +----- ext | | | +----- kde | +----- sdl