This page provides information and resources about porting applications from Xlib to XCB. It discusses the Xlib compatibility layer, provides various examples, conglomerates past mailing list posts related to porting, and hopefully will become an important reference for developers who wish to utilize the power and simplicity of XCB by reprogramming their applications to it.
The Big Picture
The recommended way to port an application from Xlib to XCB is to begin by converting the internal interfaces and structures from Xlib types to XCB. For libraries, a two step strategy is recommended. First, begin by porting the public interfaces to use XCB types. Then, provide a thin wrapper library that provides the old interface, so legacy applications can use the newly ported library without any alterations.
As mentioned elsewhere, the Xlib compatibility layer is found in versions of Xlib built with support for XCB. This allows current applications built with Xlib to begin leveraging XCB's capabilities slowly over time; the entire program doesn't have to be ported immediately. Rather, it can continue to use various Xlib functions, data types, etc. while also using XCB's facilities, structures, and other resources simultaneously.
This replaced the previous XCL library, which is described in the History section.
Once you use the Xlib functions to open a Display, you can then obtain a
xcb_connection_t and begin mixing calls using
whichever API is most convenient.