Proxies & resources

An object is an entity which known to both the client and server that has some state, changes to which are negotiated over the wire. On the client side, libwayland refers to these objects through the wl_proxy interface. These are a concrete C-friendly “proxy” for the abstract object, and provides functions which are indirectly used by the client to marshall requests into the wire format. If you review the wayland-client-core.h file, you’ll find a few low-level functions for this purpose. Generally, you don’t use these directly.

对象 object 是 client 端和 server 端相互关联的一个业务实体（entity），对象上面存储了 一些状态（state，也可以理解为参数），client 端和 server 端通过网络协商来改变两边的对象 状态值。在 client 端，libwayland 通过 wl_proxy 接口来引用这些对象。这些接口以具体的 C 语言形式实现，专门用来 “代理” 各种抽象对象的（比如前文所说的 primitive 中的 display/surface/buffer 等对象）， 并为 client 提供了一些底层函数，专门用于将请求（request）打包成线上传输格式（wire format） 的数据。如果你查看 wayland-client-core.h 文件，你就会看到这些底层函数。一般来说，不会 直接使用这些函数。

On the server, objects are abstracted through wl_resource, which is fairly similar, but have an extra degree of complexity — the server has to track which object belongs to which client. Each wl_resource is owned by a single client. Aside from this, the interface is much the same, and provides low-level abstraction for marshalling events to send to the associated client. You will use wl_resource directly on a server more often than you’ll use directly interface with wl_proxy on a client. One example of such a use is to obtain a reference to the wl_client which owns a resource that you’re manipulating out-of-context, or send a protocol error when the client attempts an invalid operation.

在 server 端，object 由 wl_resource 结构体表示，这和前面 client 端采用 wl_proxy 结构体 来表示类似，但有一点不同 — server 端必须记录某个对象具体属于哪个 client 进程。每个 wl_resource 都隶属于一个独立的 client 进程。除了刚才说的那一点不同之外，server 端的接口跟 client 端基本 相同，同时还提供了底层抽象层，用于将事件（event）打包并发送给对应的 client 端。你在 server 端 直接使用 wl_resource 会比在 client 端直接使用wl_proxy 更频繁。举一个直接使用 wl_resource 的例子： 当你想要在 server 端操作某些脱离了当前上下文的资源时，你可以通过 wl_resource 来获得这些资源 所对应的 wl_client 的引用（通过 wl_client 你就可以获得这些资源了），或者在 client 端试图 进行无效操作时发送一个协议错误的消息事件给 client 端。

Another level up is another set of higher-level interfaces, which most Wayland client & server code interacts with to accomplish a majority of their tasks.

另外还有一个更上层的接口集合（封装了 client 端和 server 端各种底层函数），用来与 wayland client 和 server 端代码进行交互，从而完成大部分的任务。

原文链接:https://wayland-book.com/