[previous] [index] [next]
In this tutorial we show how to force a roundtrip to the server to make sure an action completed.
We'll change our example from Tutorial 2 slightly and add the extra code to implement the roundtrip.
Let's take the following small method first:
static int roundtrip(
struct pw_core *core,
struct pw_main_loop *loop)
{
struct spa_hook core_listener;
int pending, done = 0;
void core_event_done(
void *
object, uint32_t
id,
int seq) {
done = 1;
}
}
.done = core_event_done,
};
spa_zero(core_listener);
&core_events, NULL);
}
spa_hook_remove(&core_listener);
return 0;
}
PipeWire main-loop interface.
SPA_EXPORT int pw_main_loop_run(struct pw_main_loop *loop)
Start a main loop.
Definition: main-loop.c:149
SPA_EXPORT int pw_main_loop_quit(struct pw_main_loop *loop)
Stop a main loop.
Definition: main-loop.c:134
#define pw_core_sync(c,...)
Definition: core.h:318
#define PW_ID_CORE
Definition: core.h:49
#define pw_core_add_listener(c,...)
Definition: core.h:316
static uint32_t int seq
Definition: core.h:325
#define PW_VERSION_CORE_EVENTS
Definition: core.h:106
Core events.
Definition: core.h:105
void(* done)(void *object, uint32_t id, int seq)
Emit a done event.
Definition: core.h:126
Let's take a look at what this method does.
struct spa_hook core_listener;
spa_zero(core_listener);
&core_events, NULL);
First of all we add a listener for the events of the core object. We are only interested in the done
event in this tutorial. This is the event handler:
int pending, done = 0;
void core_event_done(
void *
object, uint32_t
id,
int seq) {
done = 1;
}
}
.done = core_event_done,
};
When the done event is received for an object with id PW_ID_CORE
and a certain sequence number seq
, this function will set the done variable to 1 and call pw_main_loop_quit()
.
Next we do:
This triggers the sync
method on the core object with id PW_ID_CORE
and sequence number 0.
Because this is a method on a proxy object, it will be executed asynchronously and the returns value will reflect this. PipeWire uses the return values of the underlying SPA (Simple Plugin API) helper objects (See also error codes).
Because all messages on the PipeWire server are handled sequentially, the sync method will be executed after all previous methods are completed. The PipeWire server will emit a done
event with the same ID and the return value of the original pw_core_sync()
method in the sequence number.
We then run the mainloop to send the messages to the server and receive the events:
When we get the done event, we can compare it to the sync method and then we know that we did a complete roundtrip and there are no more pending methods on the server. We can quit the mainloop and remove the listener:
spa_hook_remove(&core_listener);
If we add this roundtrip method to our code and call it instead of the pw_main_loop_run()
we will exit the program after all previous methods are finished. This means that the pw_core_get_registry()
call completed and thus that we also received all events for the globals on the server.
static int roundtrip(
struct pw_core *core,
struct pw_main_loop *loop)
{
struct spa_hook core_listener;
int pending, done = 0;
void core_event_done(
void *
object, uint32_t
id,
int seq) {
done = 1;
}
}
.done = core_event_done,
};
spa_zero(core_listener);
&core_events, NULL);
}
spa_hook_remove(&core_listener);
return 0;
}
static void registry_event_global(
void *
data, uint32_t
id,
uint32_t permissions,
const char *type, uint32_t
version,
{
printf(
"object: id:%u type:%s/%d\n",
id, type,
version);
}
.global = registry_event_global,
};
int main(int argc, char *argv[])
{
struct pw_core *core;
struct spa_hook registry_listener;
NULL ,
0 );
NULL ,
0 );
0 );
spa_zero(registry_listener);
®istry_events, NULL);
roundtrip(core, loop);
return 0;
}
SPA_EXPORT struct pw_main_loop * pw_main_loop_new(const struct spa_dict *props)
Create a new main loop.
Definition: main-loop.c:87
SPA_EXPORT void pw_main_loop_destroy(struct pw_main_loop *loop)
Destroy a main loop.
Definition: main-loop.c:98
SPA_EXPORT void pw_init(int *argc, char **argv[])
Initialize PipeWire.
Definition: pipewire.c:479
Represents an object on the client side.
SPA_EXPORT void pw_proxy_destroy(struct pw_proxy *proxy)
Destroy a proxy object.
Definition: proxy.c:232
void pw_context_destroy(struct pw_context *context)
destroy a context object, all resources except the main_loop will be destroyed
struct pw_context * pw_context_new(struct pw_loop *main_loop, struct pw_properties *props, size_t user_data_size)
Make a new context object for a given main_loop.
SPA_EXPORT struct pw_core * pw_context_connect(struct pw_context *context, struct pw_properties *properties, size_t user_data_size)
Definition: core.c:405
#define PW_VERSION_REGISTRY_EVENTS
Definition: core.h:413
int pw_core_disconnect(struct pw_core *core)
disconnect and destroy a core
Definition: core.c:492
#define PW_VERSION_REGISTRY
Definition: core.h:42
#define pw_registry_add_listener(p,...)
Registry.
Definition: core.h:491
struct pw_loop * pw_main_loop_get_loop(struct pw_main_loop *loop)
Get the loop implementation.
Definition: main-loop.c:121
uint32_t version
Definition: core.h:107
Registry events.
Definition: core.h:412
Definition: pipewire.c:73
Update client properties.
To compile the simple test application, copy it into a tutorial3.c file and use:
gcc -Wall tutorial3.c -o tutorial3 $(pkg-config --cflags --libs libpipewire-0.3)
Now that our program completes, we can take a look at how we can destroy the objects we created. Let's destroy each of them in reverse order that we created them:
The registry is a proxy and can be destroyed with the generic proxy destroy method. After destroying the object, you should not use it anymore. It is an error to destroy an object more than once.
We can disconnect from the server with:
This will also destroy the core proxy object and will remove the proxies that might have been created on this connection.
We can finally destroy our context and mainloop to conclude this tutorial:
[previous] [index] [next]