Using wl_compositor

They say naming things is one of the most difficult problems in computer science, and here we are, with evidence in hand. The wl_compositor global is the Wayland compositor’s, er, compositor. Through this interface, you may send the server your windows for presentation, to be composited with the other windows being shown alongside it. The compositor has two jobs: the creation of surfaces and regions.

人们常说，命名是计算机科学中最困难的问题之一，就像现在这样。wl_compositor global对象是这个 Wayland compositor 的 compositor。通过这个接口，你可以把你的窗口发给 server，以便（server）将它和其他窗口混合，显示（在屏幕上）。合成器有两项工作：创建 surface 和创建 region。

To quote the spec, a Wayland surface has a rectangular area which may be displayed on zero or more outputs, present buffers, receive user input, and define a local coordinate system. We’ll take all of these apart in detail later, but let’s start with the basics: obtaining a surface and attaching a buffer to it. To obtain a surface, we first bind to the wl_compositor global. By extending the example from chapter 5.1 we get the following:

如 Spec 定义，一个 Wayland surface 有一个矩形的区域，可以在零个或者多个 output 上显示，承载 buffer，接收用户的输入，或者定义一个局部的坐标。稍后我们会详细介绍这些细节，目前先让我们从最基础的开始：获取一个 surface 并且为其附加 buffer。为了获取一个 surface，我们首先需要绑定 global 对象 wl_compositor。如下，扩展第 5.1章中的实列：

struct our_state {
    // ...
    struct wl_compositor *compositor;
    // ...
};

static void
registry_handle_global(void *data, struct wl_registry *wl_registry,
		uint32_t name, const char *interface, uint32_t version)
{
    struct our_state *state = data;
    if (strcmp(interface, wl_compositor_interface.name) == 0) {
        state->compositor = wl_registry_bind(
            wl_registry, name, &wl_compositor_interface, 4);
    }
}

int
main(int argc, char *argv[])
{
    struct our_state state = { 0 };
    // ...
    wl_registry_add_listener(registry, &registry_listener, &state);
    // ...
}

Note that we’ve specified version 4 when calling wl_registry_bind, which is the latest version at the time of writing. With this reference secured, we can create a wl_surface:

请注意我们在调用 wl_registry_bind 时指定了版本 4，（此版本）是撰写本文时的最新版本。在正确使用调用函数后，将创建一个 wl_surface。

struct wl_surface *surface = wl_compositor_create_surface(state.compositor);

Before we can present it, we must first attach a source of pixels to it: a wl_buffer.

在真正显示它之前，需要首先为它添加一个像素源：一个 wl_buffer。

原文链接:https://wayland-book.com/