Wayland入门教程08.08：Protocol说明

在上一篇Wayland入门教程08.07：shell stable协议中，我们操作的界面是客户端，鼠标点击、窗口移动、窗口大小、键盘输入都是由客户端捕获，然后通过协议发送给服务端。这个协议Wayland由提供默认的，如果默认的满足不了需求，可以自定义协议。协议格式为XML，使用wayland-scanner程序转换为代码。

生成代码

在makefile文件中使用命令直接导出为代码

WAYLAND_FLAGS = $(shell pkg-config wayland-client --cflags --libs)
WAYLAND_PROTOCOLS_DIR = $(shell pkg-config wayland-protocols --variable=pkgdatadir)
WAYLAND_SCANNER = $(shell pkg-config --variable=wayland_scanner wayland-scanner)

XDG_SHELL_PROTOCOL = $(WAYLAND_PROTOCOLS_DIR)/stable/xdg-shell/xdg-shell.xml

HEADERS=xdg-shell-client-protocol.h
SOURCES=xdg-shell-protocol.c

all: $(HEADERS) $(SOURCES)

$(HEADERS):
	$(WAYLAND_SCANNER) client-header $(XDG_SHELL_PROTOCOL) $@

$(SOURCES):
	$(WAYLAND_SCANNER) private-code $(XDG_SHELL_PROTOCOL) $@

clean:
	rm -rf $(HEADERS) $(SOURCES)

从pkg-config中提取变量值，然后调用wayland-scanner加上参数生成h/c文件。

执行命令，可以生成代码文件

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hyper@wayland:~/scan$ make
/usr/bin/wayland-scanner client-header //usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell-client-protocol.h
/usr/bin/wayland-scanner private-code //usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell-protocol.c

代码对应

协议中的部分内容

 <interface name="xdg_positioner" version="6">
   ...
   <enum name="gravity">
     <entry name="none" value="0"/>
     <entry name="top" value="1"/>
     <entry name="bottom" value="2"/>
     <entry name="left" value="3"/>
     <entry name="right" value="4"/>
     <entry name="top_left" value="5"/>
     <entry name="bottom_left" value="6"/>
     <entry name="top_right" value="7"/>
     <entry name="bottom_right" value="8"/>
   </enum>

   <request name="set_gravity">
     <description summary="set child surface gravity">
Defines in what direction a surface should be positioned, relative to
the anchor point of the parent surface. If a corner gravity is
specified (e.g. 'bottom_right' or 'top_left'), then the child surface
will be placed towards the specified gravity; otherwise, the child
surface will be centered over the anchor point on any axis that had no
gravity specified. If the gravity is not in the ‘gravity’ enum, an
invalid_input error is raised.
     </description>
     <arg name="gravity" type="uint" enum="gravity"
   summary="gravity direction"/>
   </request>

   ...

 </interface>

enum字段的gravity在头文件中对应

#ifndef XDG_POSITIONER_GRAVITY_ENUM
#define XDG_POSITIONER_GRAVITY_ENUM
enum xdg_positioner_gravity {
	XDG_POSITIONER_GRAVITY_NONE = 0,
	XDG_POSITIONER_GRAVITY_TOP = 1,
	XDG_POSITIONER_GRAVITY_BOTTOM = 2,
	XDG_POSITIONER_GRAVITY_LEFT = 3,
	XDG_POSITIONER_GRAVITY_RIGHT = 4,
	XDG_POSITIONER_GRAVITY_TOP_LEFT = 5,
	XDG_POSITIONER_GRAVITY_BOTTOM_LEFT = 6,
	XDG_POSITIONER_GRAVITY_TOP_RIGHT = 7,
	XDG_POSITIONER_GRAVITY_BOTTOM_RIGHT = 8,
};
#endif /* XDG_POSITIONER_GRAVITY_ENUM */

request字段的set_gravity对应头文件的函数为

static inline void
xdg_positioner_set_gravity(struct xdg_positioner *xdg_positioner, uint32_t gravity)
{
	wl_proxy_marshal_flags((struct wl_proxy *) xdg_positioner,
			 XDG_POSITIONER_SET_GRAVITY, NULL, wl_proxy_get_version((struct wl_proxy *) xdg_positioner), 0, gravity);
}

对应的实现部分为

static const struct wl_message xdg_positioner_requests[] = {
	{ "destroy", "", xdg_shell_types + 0 },
	{ "set_size", "ii", xdg_shell_types + 0 },
	{ "set_anchor_rect", "iiii", xdg_shell_types + 0 },
	{ "set_anchor", "u", xdg_shell_types + 0 },
	{ "set_gravity", "u", xdg_shell_types + 0 },
	{ "set_constraint_adjustment", "u", xdg_shell_types + 0 },
	{ "set_offset", "ii", xdg_shell_types + 0 },
	{ "set_reactive", "3", xdg_shell_types + 0 },
	{ "set_parent_size", "3ii", xdg_shell_types + 0 },
	{ "set_parent_configure", "3u", xdg_shell_types + 0 },
};

WL_PRIVATE const struct wl_interface xdg_positioner_interface = {
	"xdg_positioner", 6,
	10, xdg_positioner_requests,
	0, NULL,
};