Wayland开发入门教程08：获取全局对象

Wayland全局对象

几乎所有的Wayland API都需要Wayland全局对象作为参数。Wayland全局对象：

wl_display：表示与服务器的连接。
wl_registry：全局对象注册表，全局对象需要通过它获取。
wl_compositor：窗口合成器，也是服务器。
wl_shm：内存管理器，与窗口合成器共享内存用。
wl_shell：支持窗口操作功能（2023.5.19 Ubuntu 22.04.2 LTS时已废弃）。
wl_seat：输入设备管理器。
wl_pointer：代表鼠标设备。
wl_keyboard：代表键盘设备。

Wayland没有提供Get函数来获取以上全局对象，只能通过wl_registry获取全局对象。

首先创建wl_registry_listener对象：

static struct wl_registry_listener s_registryListener
{
    .global = on_global_added,
    .global_remove = on_global_removed
};

.global和.global_remove是此结构体提供的两个回调函数指针，我们要自己实现这些函数。

也可以直接写

static struct wl_registry_listener s_registryListener
{
    on_global_added,
    on_global_removed
};

看你喜欢哪一种写法。

然后设置回调函数

struct wl_registry *reg = wl_display_get_registry(disp);
if (!reg)
{
    fprintf(stderr, "Failed to get registry!\n");
}

fprintf(stderr, "Got registry OK!\n");

wl_registry_add_listener(reg, &s_registryListener, NULL);

在回调函数中继续处理。

static void on_global_added(void *data,
                            struct wl_registry *wl_registry,
                            uint32_t name,
                            const char *interface,
                            uint32_t version)
{
    (void)data;
    (void)wl_registry;
    fprintf(stderr, "Global added: %s, v %d (name %d)\n", interface, version, name);
}

在此就只是输出名称、版本。

编译运行，Ubuntu21.04输出为：

XDG_RUNTIME_DIR = /run/user/1000
Connect OK!
Got registry OK!
 Global added: wl_drm, v2 (name 1)
 Global added: wl_compositor, v4 (name 2)
 Global added: wl_shm, v1 (name 3)
 Global added: wl_output, v2 (name 4)
 Global added: zxdg_output_manager_v1, v3 (name 5)
 Global added: wl_data_device_manager, v3 (name 6)
 Global added: zwp_primary_selection_device_manager_v1, v1 (name 7)
 Global added: gtk_primary_selection_device_manager, v1 (name 8)
 Global added: wl_subcompositor, v1 (name 9)
 Global added: xdg_wm_base, v3 (name 10)
 Global added: zxdg_shell_v6, v1 (name 11)
 Global added: wl_shell, v1 (name 12)
 Global added: gtk_shell1, v3 (name 13)
 Global added: wp_viewporter, v1 (name 14)
 Global added: zwp_pointer_gestures_v1, v1 (name 15)
 Global added: zwp_tablet_manager_v2, v1 (name 16)
 Global added: wl_seat, v5 (name 17)
 Global added: zwp_relative_pointer_manager_v1, v1 (name 18)
 Global added: zwp_pointer_constraints_v1, v1 (name 19)
 Global added: zxdg_exporter_v1, v1 (name 20)
 Global added: zxdg_importer_v1, v1 (name 21)
 Global added: zwp_linux_dmabuf_v1, v3 (name 22)
 Global added: zwp_keyboard_shortcuts_inhibit_manager_v1, v1 (name 23)
 Global added: zwp_text_input_manager_v3, v1 (name 24)
 Global added: gtk_text_input_manager, v1 (name 25)
Sleeping for 3 secs...

完整代码在Wayland_Freshman的08.interface中。

如果是使用wldbg进行测试，需要注意的是wldbg捕获到连接信号后阻塞，如果要继续输出registry信息需要按下c。

hyper@ubuntu:~$ wldbg -s
Listening for incoming connections...
Stopped on the first message
[interface2     ] C: wl_display@1.get_registry(new id wl_registry@2)
(wldbg) c
[interface2     ] S: wl_registry@2.global(1, 7:"wl_drm", 2)
[interface2     ] S: wl_registry@2.global(2, 14:"wl_compositor", 4)
[interface2     ] S: wl_registry@2.global(3, 7:"wl_shm", 1)
[interface2     ] S: wl_registry@2.global(4, 10:"wl_output", 2)
[interface2     ] S: wl_registry@2.global(5, 23:"zxdg_output_manager_v1", 3)
[interface2     ] S: wl_registry@2.global(6, 23:"wl_data_device_manager", 3)
[interface2     ] S: wl_registry@2.global(7, 40:"zwp_primary_selection_device_manager_v1", 1)
[interface2     ] S: wl_registry@2.global(8, 37:"gtk_primary_selection_device_manager", 1)
[interface2     ] S: wl_registry@2.global(9, 17:"wl_subcompositor", 1)
[interface2     ] S: wl_registry@2.global(10, 12:"xdg_wm_base", 3)
[interface2     ] S: wl_registry@2.global(11, 14:"zxdg_shell_v6", 1)
[interface2     ] S: wl_registry@2.global(12, 9:"wl_shell", 1)
[interface2     ] S: wl_registry@2.global(13, 11:"gtk_shell1", 3)
[interface2     ] S: wl_registry@2.global(14, 14:"wp_viewporter", 1)
[interface2     ] S: wl_registry@2.global(15, 24:"zwp_pointer_gestures_v1", 1)
[interface2     ] S: wl_registry@2.global(16, 22:"zwp_tablet_manager_v2", 1)
[interface2     ] S: wl_registry@2.global(17, 8:"wl_seat", 5)
[interface2     ] S: wl_registry@2.global(18, 32:"zwp_relative_pointer_manager_v1", 1)
[interface2     ] S: wl_registry@2.global(19, 27:"zwp_pointer_constraints_v1", 1)
[interface2     ] S: wl_registry@2.global(20, 17:"zxdg_exporter_v1", 1)
[interface2     ] S: wl_registry@2.global(21, 17:"zxdg_importer_v1", 1)
[interface2     ] S: wl_registry@2.global(22, 20:"zwp_linux_dmabuf_v1", 3)
[interface2     ] S: wl_registry@2.global(23, 42:"zwp_keyboard_shortcuts_inhibit_manager_v1", 1)
[interface2     ] S: wl_registry@2.global(24, 26:"zwp_text_input_manager_v3", 1)
[interface2     ] S: wl_registry@2.global(25, 23:"gtk_text_input_manager", 1)
[interface2     ] C: wl_registry@2.bind(2, 14:"wl_compositor", 1, new id [unknown]@3)
[interface2     ] C: wl_registry@2.bind(12, 9:"wl_shell", 1, new id [unknown]@4)
[interface2     ] C: wl_display@1.sync(new id wl_callback@5)
[interface2     ] S: wl_callback@5.done(6998)
[interface2     ] S: wl_display@1.delete_id(5)