Chapter 4 deals with the display, the process of connecting to the server. The process, for clients, is very similar to opening a display in X. We can open a display based on an environment variable, or directly via a file descriptor. The process for servers is shown: the display is created and the socked is added, possibly automatically.

The routine wl_display_run run libwayland's internal event loop on the server. It will process events and block until the display terminates via wl_display_terminate. You can add file descriptors, timers and handle signals with its own event loop implementation, so the programmer does not have to implement their own. But it is possible to manually process client updates: wl_event_loop_get gets a poll-able file descriptor.

For clients, the event loop must be implemented by the programmer. wl_display_dispatch dispatches the queued events for the programmer to process them.

Chapter 5 deals with the wl_registry interface. If I understood correctly, when creating an object, the server an event for each global object on the server. Once the object is created, we can use its interface. An example is shown, where we connect to the display, obtain the object registry and add a listener to it, implement a prototype of weston-info, from the weston project. Then, the chater shows how to do registering of globals in the server side.

Chapter 6 deals with the wl_buffer and wl_surface interfaces. Through the wl_compositor interface, we send the window to the server to be composited with the other windows. Surface seems to be what a Window is to X11, a rectangualar area with a local coordinate system that can receive input and be displayed. Before being presented, we need to attach a wl_buffer to it.
I did not try the examples, as I couldn't use my Linux machine this week. I'll try do the compositing thing next week.