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client: Add wl_event_queue for multi-thread dispatching

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This introduces wl_event_queue, which is what will make multi-threaded
wayland clients possible and useful.  The driving use case is that of a
GL rendering thread that renders and calls eglSwapBuffer independently of
a "main thread" that owns the wl_display and handles input events and
everything else.  In general, the EGL and GL APIs have a threading model
that requires the wayland client library to be usable from several threads.
Finally, the current callback model gets into trouble even in a single
threaded scenario: if we have to block in eglSwapBuffers, we may end up
doing unrelated callbacks from within EGL.

The wl_event_queue mechanism lets the application (or middleware such as
EGL or toolkits) assign a proxy to an event queue.  Only events from objects
associated with the queue will be put in the queue, and conversely,
events from objects associated with the queue will not be queue up anywhere
else.  The wl_display struct has a built-in event queue, which is considered
the main and default event queue.  New proxies are associated with the
same queue as the object that created them (either the object that a
request with a new-id argument was sent to or the object that sent an
event with a new-id argument).  A proxy can be moved to a different event
queue by calling wl_proxy_set_queue().

A subsystem, such as EGL, will then create its own event queue and associate
the objects it expects to receive events from with that queue.  If EGL
needs to block and wait for a certain event, it can keep dispatching event
from its queue until that events comes in.  This wont call out to unrelated
code with an EGL lock held.  Similarly, we don't risk the main thread
handling an event from an EGL object and then calling into EGL from a
different thread without the lock held.
This commit is contained in:
Kristian Høgsberg 2012-10-05 13:49:48 -04:00
parent de961dc1f3
commit 385fe30e8b
2 changed files with 123 additions and 35 deletions
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8
src/wayland-client.h
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@ -32,6 +32,9 @@ extern "C" {
struct wl_proxy;
struct wl_display;
struct wl_event_queue;
void wl_event_queue_destroy(struct wl_event_queue *queue);
void wl_proxy_marshal(struct wl_proxy *p, uint32_t opcode, ...);
struct wl_proxy *wl_proxy_create(struct wl_proxy *factory,
@ -46,6 +49,7 @@ int wl_proxy_add_listener(struct wl_proxy *proxy,
void wl_proxy_set_user_data(struct wl_proxy *proxy, void *user_data);
void *wl_proxy_get_user_data(struct wl_proxy *proxy);
uint32_t wl_proxy_get_id(struct wl_proxy *proxy);
void wl_proxy_set_queue(struct wl_proxy *proxy, struct wl_event_queue *queue);
void *wl_display_bind(struct wl_display *display,
uint32_t name, const struct wl_interface *interface);
@ -74,8 +78,12 @@ struct wl_display *wl_display_connect_to_fd(int fd);
void wl_display_disconnect(struct wl_display *display);
int wl_display_get_fd(struct wl_display *display);
int wl_display_dispatch(struct wl_display *display);
int wl_display_dispatch_queue(struct wl_display *display,
struct wl_event_queue *queue);
int wl_display_flush(struct wl_display *display);
void wl_display_roundtrip(struct wl_display *display);
struct wl_event_queue *wl_display_create_queue(struct wl_display *display);
struct wl_global_listener;
typedef void (*wl_display_global_func_t)(struct wl_display *display,