Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
In computing, a binding from a programming language to a library or OS service is an API providing that service in the language.Many software libraries are written in systems programming languages such as C or C++...
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
Xlib is an X Window System protocol client library written in the C programming language. It contains functions for interacting with an X server. These functions allow programmers to write programs without knowing the details of the protocol...
In computer software, an application binary interface describes the low-level interface between an application program and the operating system or another application.- Description :...
compatibility with both Xlib and XCB, providing an incremental porting path. Xlib/XCB uses the protocol layer of Xlib, but replaces the Xlib transport layer with XCB, and provides access to the underlying XCB connection for direct use of XCB. Most operating systems use Xlib/XCB for their libX11, because it allows an application to open a single connection to the X server and use both XCB and Xlib, possibly through a mixture of libraries designed for one or the other.
The X Window System core protocol is the base protocol of the X Window System, which is a networked windowing system for bitmap displays used to build graphical user interfaces on Unix, Unix-like, and other operating systems...
.
Secondary goals include to make the C interface asynchronous
Asynchronous communication
In telecommunications, asynchronous communication is transmission of data without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream. Any timing required to recover data from the communication symbols is encoded within the symbols...
, facilitate better multithreading and make it easier to implement extensions (via XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
protocol descriptions).
The core and extension protocol descriptions are in XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
creating the C bindings. (Previous versions used XSLT
XSLT
XSLT is a declarative, XML-based language used for the transformation of XML documents. The original document is not changed; rather, a new document is created based on the content of an existing one. The new document may be serialized by the processor in standard XML syntax or in another format,...
m4 is a general purpose macro processor designed by Brian Kernighan and Dennis Ritchie. m4 is an extension of an earlier macro processor m3, written by Ritchie for the AP-3 minicomputer.-Use:...
.)
A further goal is to be able to use these protocol descriptions to create protocol documentation, more language bindings, and server-side stubs.
Massey and others have worked to prove key portions of XCB formally correct
Formal verification
In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of intended algorithms underlying a system with respect to a certain formal specification or property, using formal methods of mathematics .- Usage :Formal verification can be...
The Z notation , named after Zermelo–Fraenkel set theory, is a formal specification language used for describing and modelling computing systems. It is targeted at the clear specification of computer programs and computer-based systems in general.-History:...
. (Xlib has long been known to contain errors.)
Example
/* Simple XCB application drawing a box in a window */
/* to compile it use :
gcc -Wall x.c -lxcb
include
include
include
int main(void)
{
xcb_connection_t *c;
xcb_screen_t *s;
xcb_window_t w;
xcb_gcontext_t g;
xcb_generic_event_t *e;
uint32_t mask;
uint32_t values[2];
int done = 0;
xcb_rectangle_t r = { 20, 20, 60, 60 };
/* open connection with the server */
c = xcb_connect(NULL,NULL);
if (xcb_connection_has_error(c)) {
printf("Cannot open display\n");
exit(1);
}
/* get the first screen */
s = xcb_setup_roots_iterator( xcb_get_setup(c) ).data;
/* create black graphics context */
g = xcb_generate_id(c);
w = s->root;
mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
values[0] = s->black_pixel;
values[1] = 0;
xcb_create_gc(c, g, w, mask, values);
An interface description language , or IDL for short, is a specification language used to describe a software component's interface...
to model X11 protocol in language-neutral way and facilitate generation of bindings to other programming languages. libxcb itself is implemented as a code generator and a tiny C stub of utility functions.
freedesktop.org is a project to work on interoperability and shared base technology for free software desktop environments for the X Window System on Linux and other Unix-like operating systems. It was founded by Havoc Pennington from Red Hat in March 2000.The organisation focuses on the user....
