原文链接：https://my.oschina.net/txl/blog/266931

Wayland窗口绘制

    Wayland窗口绘制有两种：1) 共享内存方式、2)EGL。

本文使用方式1绘制窗口。

Wayland窗口：wl_surface

    Wayland窗口绘制完全由程序控制，包括标题栏绘制，边框绘制，窗口移动，改变大小等。 其中与窗口绘制有关的函数有：

wl_surface_attach() 将缓存绑定到窗口上，窗口大小会根据缓存重新计算。

wl_surface_damage() 标记窗口失效的区域

wl_surface_commit() 缓存提交请求，合成器会锁定提交的缓存，直到下一次wl_surface_attach或合成器主动释放。

wl_surface_frame() 申请帧绘制回调，每当绘制完一帧就发送wl_callback::done消息。

Walyand缓存：wl_buffer

    Wayland窗口显示的内容由wl_buffer负责。Wayland与X Server不同，Wayland只支持客户端直接绘制，合成器不提供对wl_buffer的绘制操作。与wl_buffer有关的函数有：

wl_shm_create_pool() 创建一个缓存池，缓存池可以mmap到程序的内存空间中。

wl_shm_pool_create() 创建一个wl_buffer。

示例代码：

lpBuffer->data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	//lpBuffer->data == MAP_FAILED

	HSHMPOOL pool = wl_shm_create_pool(wlGetRegistry()->s_shm, fd, size);
	lpBuffer->buffer = wl_shm_pool_create_buffer(pool, 0, width, height, stride, WL_SHM_FORMAT_XRGB8888);

其中：fd是临时文件，大小为size，用于mmap用。

窗口绘制：

void buffer_release(void *data, struct wl_buffer *buffer)
{
	LPPAINTBUFFER lpBuffer = data;
	lpBuffer->busy = 0;
}

static const struct wl_buffer_listener buffer_listener = 
{
	.release = buffer_release
};

void _wlCreatePaintStructure(int width, int height, LPPAINTBUFFER lpBuffer)
{
	int stride = width * 4;
	int size = stride * height;

	char filename[] = "/tmp/weston-shared-XXXXXX";
	int fd = mkstemp(filename);
	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
	unlink(filename);
	ftruncate(fd, size);

	lpBuffer->busy = 0;

	lpBuffer->data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	//lpBuffer->data == MAP_FAILED

	HSHMPOOL pool = wl_shm_create_pool(wlGetRegistry()->s_shm, fd, size);
	lpBuffer->buffer = wl_shm_pool_create_buffer(pool, 0, width, height, stride, WL_SHM_FORMAT_XRGB8888);
	wl_buffer_add_listener(lpBuffer->buffer, &buffer_listener, lpBuffer);
	wl_shm_pool_destroy(pool);
	close(fd);
}

void wlBeginPaint(HSURFACE surface, LPPAINTSTRUCTURE lpPaint)
{
	LPSURFACEPRIVATE _priv = _wlGetSurfacePrivate(surface);
	if (!_priv->buffer[0].busy && _priv->buffer[0].buffer)
	{
		lpPaint->buffer = &_priv->buffer[0];
	}
	else if (!_priv->buffer[1].busy && _priv->buffer[1].buffer)
	{
		lpPaint->buffer = &_priv->buffer[1];
	}
	else
	{
		SIZE sz = wlGetSurfaceSize(surface);
		_wlCreatePaintStructure(sz.width, sz.height, &_priv->buffer[0]);
		lpPaint->buffer = &_priv->buffer[0];
	}
}

void wlEndPaint(HSURFACE surface, LPPAINTSTRUCTURE lpPaint)
{
	lpPaint->buffer->busy = 1;
	wl_surface_attach(surface, lpPaint->buffer->buffer, 0, 0);
	SIZE sz = wlGetSurfaceSize(surface);
	wl_surface_damage(surface, 0, 0, sz.width, sz.height);
	wl_surface_commit(surface);
}

void frame_listener_done(void *data, HCALLBACK callback, uint32_t time)
{
	HSURFACE surface = (HSURFACE)data;
	/* 每次都需要重新设置回调函数 */
	_wlSetFrameListener(surface);
	
	/* 绘制一帧 */
	_wlDrawFrame(surface, time);
}

static struct wl_callback_listener frame_listener = { frame_listener_done };

void _wlSetFrameListener(HSURFACE surface)
{
	static struct wl_callback_listener frame_listener;
	frame_listener.done = frame_listener_done;
	HCALLBACK callback = wl_surface_frame(surface);
	wl_callback_add_listener(callback, &frame_listener, surface);
}

void _wlDrawFrame(HSURFACE surface, uint32_t time)
{
	PAINTSTRUCTURE ps;
	memset(&ps, 0, sizeof(ps));
	wlBeginPaint(surface, &ps);
	wlCallPaintProc(surface, &ps, time);
	wlEndPaint(surface, &ps);
}

void wlSetPaintProc(HSURFACE surface, REPAINTPROC surfaceproc)
{
	_wlGetSurfacePrivate(surface)->surfaceproc = surfaceproc;
	_wlSetFrameListener(surface);
	_wlDrawFrame(surface, 0);
}

转载于:https://my.oschina.net/txl/blog/266931