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server: add wl_global_remove

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This commit adds a new wl_global_remove function that just sends a global
remove event without destroying it. See [1] for details.

Removing a global is racy, because clients have no way to acknowledge they
received the removal event.

It's possible to mitigate the issue by sending the removal event, waiting a
little and then destructing the global for real. The "wait a little" part is
compositor policy.

[1]: https://gitlab.freedesktop.org/wayland/wayland/issues/10

Signed-off-by: Simon Ser <contact@emersion.fr>
This commit is contained in:
Simon Ser 2019-07-20 23:36:29 +03:00
parent 11623e8fdd
commit 39852f1146
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GPG Key ID: 0FDE7BE0E88F5E48
2 changed files with 43 additions and 2 deletions
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3
src/wayland-server-core.h
View File

@ -246,6 +246,9 @@ wl_global_create(struct wl_display *display,
int version,
void *data, wl_global_bind_func_t bind);
void
wl_global_remove(struct wl_global *global);
void
wl_global_destroy(struct wl_global *global);

42
src/wayland-server.c
View File

@ -25,6 +25,7 @@
#define _GNU_SOURCE
#include <stdbool.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
@ -112,6 +113,7 @@ struct wl_global {
void *data;
wl_global_bind_func_t bind;
struct wl_list link;
bool removed;
};
struct wl_resource {
@ -992,7 +994,7 @@ display_get_registry(struct wl_client *client,
&registry_resource->link);
wl_list_for_each(global, &display->global_list, link)
if (wl_global_is_visible(client, global))
if (wl_global_is_visible(client, global) && !global->removed)
wl_resource_post_event(registry_resource,
WL_REGISTRY_GLOBAL,
global->name,
@ -1208,6 +1210,7 @@ wl_global_create(struct wl_display *display,
global->version = version;
global->data = data;
global->bind = bind;
global->removed = false;
wl_list_insert(display->global_list.prev, &global->link);
wl_list_for_each(resource, &display->registry_resource_list, link)
@ -1220,15 +1223,50 @@ wl_global_create(struct wl_display *display,
return global;
}
/** Remove the global
*
* \param global The Wayland global.
*
* Broadcast a global remove event to all clients without destroying the
* global. This function can only be called once per global.
*
* wl_global_destroy() removes the global and immediately destroys it. On
* the other end, this function only removes the global, allowing clients
* that have not yet received the global remove event to continue to bind to
* it.
*
* This can be used by compositors to mitigate clients being disconnected
* because a global has been added and removed too quickly. Compositors can call
* wl_global_remove(), then wait an implementation-defined amount of time, then
* call wl_global_destroy(). Note that the destruction of a global is still
* racy, since clients have no way to acknowledge that they received the remove
* event.
*
* \since 1.17.90
*/
WL_EXPORT void
wl_global_destroy(struct wl_global *global)
wl_global_remove(struct wl_global *global)
{
struct wl_display *display = global->display;
struct wl_resource *resource;
if (global->removed)
wl_abort("wl_global_remove: called twice on the same "
"global '%s@%"PRIu32"'", global->interface->name,
global->name);
wl_list_for_each(resource, &display->registry_resource_list, link)
wl_resource_post_event(resource, WL_REGISTRY_GLOBAL_REMOVE,
global->name);
global->removed = true;
}
WL_EXPORT void
wl_global_destroy(struct wl_global *global)
{
if (!global->removed)
wl_global_remove(global);
wl_list_remove(&global->link);
free(global);
}