1.7 KiB
XCB
XCB is a library for communicating with the X-Windows system used on Linux, FreeBSD, and other Unix-like operating systems. XCB's interface is written in C.
- Connecting, Verifying Connection, and Disconnecting the server.
Connecting.
X-Windows is a server. It listens for events (keyboard events, mouse events, timer events from connected programs, etc.) and "stores" the results on a display, which is intended to be seen with the human eye. A display is made up of one or more screens. Screens can be literal (one of the physical devices in a multi-monitor setup) or virtual (a virtualized desktop where the window manager supports different "pages" on the same monitor), or even just parts of the same physical screen space broken up by some logic.
To connect to X via XCB, you use the xcb_connect function. It takes two
arguments, a string with the name of the display, and a
pointer-to-int to the preferred screen. It returns an opaque data
structure, 'xcb_connection_t'.
xcb_connection_t* xcbConnection = xcb_connect(const char* display, int* screen);
There are variants for connection-with-authorization, and connection-with-file-descriptor.
This function always returns an allocated structure, even on failure. You must test for failure with:
int error = xcb_connection_has_error(xcb_connection_t* xcbConnection);
The error is an number defined in xcb.h. See that file for the list
of possible failure modes.
Disconnecting
You must close the connection when you are finished. In the event of a connection failure, you must still call this function to free the memory XCB used to report the connection failure:
void xcb_disconnect(xcb_connection_t* xcbConnection);