Commit d9154473 authored by Olivier Fourdan's avatar Olivier Fourdan Committed by Pekka Paalanen

wayland-server: Add API to control globals visibility

Add a new API to let compositor decide whether or not a wl_global
should be advertised to the clients via wl_registry_bind() or

By using its own filter, the compositor can decide which wl_global would
be listed to clients.

Compositors can use this mechanism to hide their own private interfaces
that regular clients should not use.

- Hiding interfaces that expose compositor implementation details
  makes it harder for clients to identify the compositor. Therefore
  clients are a little less likely to develop compositor-specific
  workarounds instead of reporting problems upstream.

- Hiding can be used to diminish the problems from missing namespacing:
  if two compositors happen to use the same named global with
  different interfaces for their special-purpose clients, the client
  expecting the different interface would probably never see it
Signed-off-by: default avatarOlivier Fourdan <>
Reviewed-by: Jonas Ådahl's avatarJonas Ådahl <>
Reviewed-by: default avatarYong Bakos <>
Acked-by: Pekka Paalanen's avatarPekka Paalanen <>
Reviewed-by: Pekka Paalanen's avatarPekka Paalanen <>
parent 2f72d0a8
......@@ -28,6 +28,7 @@
#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include "wayland-util.h"
#include "wayland-version.h"
......@@ -168,6 +169,30 @@ wl_global_create(struct wl_display *display,
wl_global_destroy(struct wl_global *global);
/** A filter function for wl_global objects
* \param client The client object
* \param global The global object to show or hide
* \param data The user data pointer
* A filter function enables the server to decide which globals to
* advertise to each client.
* When a wl_global filter is set, the given callback funtion will be
* called during wl_global advertisment and binding.
* This function should return true if the global object should be made
* visible to the client or false otherwise.
typedef bool (*wl_display_global_filter_func_t)(const struct wl_client *client,
const struct wl_global *global,
void *data);
wl_display_set_global_filter(struct wl_display *display,
wl_display_global_filter_func_t filter,
void *data);
struct wl_client *
wl_client_create(struct wl_display *display, int fd);
......@@ -101,6 +101,9 @@ struct wl_display {
struct wl_signal create_client_signal;
struct wl_array additional_shm_formats;
wl_display_global_filter_func_t global_filter;
void *global_filter_data;
struct wl_global {
......@@ -769,6 +772,21 @@ wl_client_destroy(struct wl_client *client)
/* Check if a global filter is registered and use it if any.
* If no wl_global filter has been registered, this funtion will
* return true, allowing the wl_global to be visible to the wl_client
static bool
wl_global_is_visible(const struct wl_client *client,
const struct wl_global *global)
struct wl_display *display = client->display;
return (display->global_filter == NULL ||
display->global_filter(client, global, display->global_filter_data));
static void
registry_bind(struct wl_client *client,
struct wl_resource *resource, uint32_t name,
......@@ -795,6 +813,10 @@ registry_bind(struct wl_client *client,
"invalid version for global %s (%d): have %d, wanted %d",
interface, name, global->version, version);
else if (!wl_global_is_visible(client, global))
"invalid global %s (%d)", interface, name);
global->bind(client, global->data, version, id);
......@@ -850,11 +872,12 @@ display_get_registry(struct wl_client *client,
wl_list_for_each(global, &display->global_list, link)
if (wl_global_is_visible(client, global))
static const struct wl_display_interface display_interface = {
......@@ -925,6 +948,9 @@ wl_display_create(void)
display->id = 1;
display->serial = 0;
display->global_filter = NULL;
display->global_filter_data = NULL;
return display;
......@@ -999,6 +1025,37 @@ wl_display_destroy(struct wl_display *display)
/** Set a filter function for global objects
* \param display The Wayland display object.
* \param filter The global filter funtion.
* \param data User data to be associated with the global filter.
* \return None.
* Set a filter for the wl_display to advertise or hide global objects
* to clients.
* The set filter will be used during wl_global advertisment to
* determine whether a global object should be advertised to a
* given client, and during wl_global binding to determine whether
* a given client should be allowed to bind to a global.
* Clients that try to bind to a global that was filtered out will
* have an error raised.
* Setting the filter NULL will result in all globals being
* advertised to all clients. The default is no filter.
* \memberof wl_display
wl_display_set_global_filter(struct wl_display *display,
wl_display_global_filter_func_t filter,
void *data)
display->global_filter = filter;
display->global_filter_data = data;
WL_EXPORT struct wl_global *
wl_global_create(struct wl_display *display,
const struct wl_interface *interface, int version,
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