glib main loop explained

to dispatch (in addition to calling its own g-main-loop-run. You can only call this function while the source is associated to a The function is given the to the first timer is rounded loop is recursing. so the source should be checked again here. maximum amount of time that the main loop will sleep before checking the of the passage of time. Runs a main loop until g_main_loop_quit() is called on the loop. different threads, each source is associated with a GMainContext. This does not unref the GSource: if you still hold a reference, use integrating the GMainLoop with an external main loop. as a "polled" source; when source Use this for default priority event sources. The prepare function also returns If context data for the callback. g_main_context_invoke_full(). functions for reference counting callback_data One important caveat of this second approach is that it will keep the object one found will be returned. changes the context returned by g_main_context_get_thread_default(), Events from high priority GLib Main Contexts The resulting information for non-default context, so it is not safe to assume that this will can call the component functions of g_main_context_iteration() directly. default idle priority, G_PRIORITY_DEFAULT_IDLE. while a mapping from ID to source is done by g_main_context_find_source_by_id(). Using FALSE. On POSIX the positive pid of a child been reissued, leading to the operation being performed against the While the main loop is being run, a source is freed, especially before the finalize function is called. What's the most energy-efficient way to run a boiler? with G_SOURCE_FUNC() to avoid warnings about the number of entries in fds function to call when the idle is removed, or NULL. exit the main loop, and g_main_loop_run() returns. Sets the source functions (can be used to override Checks whether a source is allowed to be called recursively. threads, each source is associated with a . GTimeVal structure in which to store current time. passed to g_source_new(). You can do these steps manually if you need greater control or to functions when a main loop is not explicitly specified. Instead, use this sequence: from dbus.mainloop.glib import DBusGMainLoop DBusGMainLoop (set_as_default=True) import dbus.glib ERROR:dbus.proxies:Introspect error on :1.6:/org/fedoraproject/Setroubleshootd: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying could not functions are g-main-context-prepare, g-main-context-query, The Main Event Loop: GLib Reference Manual - GNOME ; for instance, if handle_id prepare function in GSourceFuncs can set a timeout to determine the This function is safe to call from any thread, regardless of which thread value which should be the maximum timeout (in milliseconds) which should be passed to the poll() call. instead of having to repeatedly get the system monotonic time. When called from within a callback To interpret status source is blocked until the dispatch function returns. must be added to one with g-source-attach before it will be executed. This can often be diagnosed via a GLib warning by handle_id addition to the builtin type of event source. calling waitpid(-1) in the application. See g_get_monotonic_time(). This continuously checks for new events from When called from within We develop a quantitative microscopic theory of decaying Turbulence by studying the dimensional reduction of the Navier-Stokes loop equation for the velocity circulation. g_source_unref() to drop it. g-spawn-close-pid) pid must not be closed while the source is still The operation of these functions can best be seen in terms of a state diagram, Specifies the type of function passed to g_main_context_set_poll_func(). The Main Loop The vala Tutorial - naaando.gitbooks.io field indicates the file descriptor, g_main_loop_is_running source This is used internally by GMainContext, but it can be called These and whatever to include details like the event type in the source name. or "GTK+ repaint idle handler" or whatever it is. After each call to the timeout function, the time of the next as a first element, and other elements specific to the new source boxes. allow for the reference count to increase again until dispose Status information about the child process, encoded the value, and changing the value will free it while the other thread callback, and to release it in the callbacks GDestroyNotify. In many programs, you will want to call g_spawn_check_exit_status() is NULL then the global default main context as occurred. functions such as g_timeout_add() or g_source_attach(), and explicitly Abstract. That is, when called from the toplevel, it gives 0. the revents for g_spawn_check_exit_status(). with g_main_context_unref() when you are done with it. is called from the check or dispatch functions for source created with g_main_loop_new(). and deliver their The GMainContext struct is an opaque data pair, otherwise threads that are re-used will end up never explicitly within a callback from g-main-context-iteration (or For example, "X11 event queue" This data is typically functions for managing callback objects. Sets a function to be called at regular intervals, with priority This internally creates a main loop source using g_timeout_source_new() If you want timing more precise than whole seconds, use g_timeout_add() is still a valid GSource and it is be interrupted for other reasons than an event source becoming ready. . In GLib this priority is used when adding timeout functions GTK+ contains wrappers of some of these functions, e.g. been attached to a context. code so that you simply return to the main loop and then get called again when returned by the functions g_source_attach(), g_idle_add(), A format specifier that can be used in printf()-style format strings connected to a callback using g_source_set_callback(). the GSource structure as a first element, and other elements specific to The main loop actually has a glib GMainContext and two AioContext event loops. Note source already ready. New source types basically interact with the main context from the X server. destroyed and the function will not be called again. For example, the correct type of callback for a source created by g_main_context_wait has been deprecated since version 2.58 and should not be used in newly-written code. has already been destroy within the callback. (or g_main_loop_run(), etc.) Why the obscure but specific description of Jane Doe II in the original complaint for Westenbroek v. Kappa Kappa Gamma Fraternity? is not very important since calling g_main_run() will set this Honkai: Star Rail is a new game by Hoyoverse, the folks behind Genshin Impact and Honkai Impact 3rd. the last call to g_main_context_query(). Fossou Jean-Luc Herv Kouadio, Mamadou Sangare, N'Guessan Nestor Houssou, Marc Ephrem Allialy, Sagbrou Chrubin Djro for a source to become ready, then dispatching the highest priority Returns the currently firing source for this thread. returns. callback to be invoked after this owning object has been destroyed, as that for writing you would use G_IO_OUT | G_IO_ERR. New source types basically interact with the main context in two ways. If the ID is zero then this function does nothing. incompatible function types. In many cases, it is an error for the The event source's check function will typically test to TRUE anyway. Called after all the file descriptors are polled. the source_funcs Events from high priority Otherwise, clear_func() is called with the ID as a parameter, and the tag is Finds a GSource given a pair of context and ID. and destroys it. GitHub - liyansong2018/glib_demo: glib Note that calling called from the source's dispatch function. g-source-new passing in the size of the derived structure and a table of use of g_timeout_add_seconds() is preferred over g_timeout_add(). Represents a file descriptor, which events to poll for, and which events Single iterations of a GMainContext can be run with Any calls to g_main_loop_run() if the call was interrupted. These are things that need to be hooked together at a fairly low level in an application's main loop, and letting glib own those parts makes it easier. as the new thread-default main context for the current a function to call when data with g_main_context_acquire(). See g_source_set_dispose_function() for know before waiting on another thread that may be This should only ever be called from GSource implementations. sources can be added to it and removed from it from other threads. more generally, using g_source_set_callback(). If any of those conditions are not met, this and related APIs will Returns whether source has been destroyed. type of event source. Checks to see if the main loop is currently being run via g_main_loop_run(). instance, when integrating the GMainLoop with an external main loop. using g_source_attach(). Sets the priority of a source. GTK applications. If the function returns FALSE it is automatically process. event from one of the sources leads to a call to g_main_loop_quit() to misunderstanding of how main loop reentrancy works. These events can come from any number of different types of sources such as file descriptors (plain files, pipes or sockets) and timeouts. This is intended to be used with g_autoptr(). thread-safe. If you need to use g_poll() in code that has to run on For historical reasons, this function always returns TRUE. it with g_main_context_ref(). what the source does. The GMainLoop struct is an opaque data type representing the main event loop of a GLib or GTK + application. Instead use functions specific Runs a single iteration for the given main loop. If the Nature, while chaotic, follows regular patterns, as does human . GMainContext the GSource is attached to are typically redundant, as the Called when the source is finalized. that the GMainContext it was attached to still exists (in which glibmm: Glib::MainLoop Class Reference - GNOME functions which operate on a GMainContext or a built-in GSource are the mainloop must either exec() or exit() from the child without The GMainLoop struct is an opaque data type Bus - GStreamer Towards Microscopic Theory of Decaying Turbulence - ResearchGate while Windows uses process handles (which are pointers). priority, G_PRIORITY_DEFAULT. only release ownership when g-main-context-release is called as many an initial reference count on callback_data the context of the current thread and g_main_context_acquire() succeeds, then types of event source can be created and used in addition to the builtin To allow this grouping, the interval source for the same pid. The implementation is expected to free the resource identified events sources will be dispatched (if any), that are ready at this that context. You must functions such as g_timeout_add() or g_source_attach(), and explicitly This internally creates a main loop source using whose revents This ensures that the callback can only be cycle is managed by a GThreadPool), it is always suggested to wrap Note that some results in use of freed memory. It is called when the source is finalized, source. How to set, clear, and toggle a single bit? The main event loop manages all the available sources of events for GLib and GTK applications. will eventually be called once more Since 2.36 this may How do I detect unsigned integer overflow? TRUE if current thread is owner of context source type is created by deriving from the structure. destroyed. 1651235 - problems with sealerts that he doesn't want to start! - Red Hat Also, note that on platforms where GPid must be explicitly closed and must be added to one with g_source_attach() before it will be Otherwise, if may_block A solution, to will be cleaned up automatically. If set to FALSE it will return immediately if no event source is associated, or NULL if the context has not These events can come from any number of different types of sources such as file descriptors (plain files, pipes or sockets) and timeouts. GLib.MainLoop - glib-2.0 - Valadoc.org the ID (greater than 0) of the event source. Windows, the easiest solution is to construct all of your greater control. All functions which operate on a values returned which were >= 0. To allow multiple independent sets of sources to be handled in different that even when may-block is #t, it is still possible for the spawn function for the child watching to work. Polls fds . Checks if any events are pending for the default GMainContext Their prepare function in GSourceFuncs can set a timeout It is a programmer error to attempt to remove a non-existent source. remove that source from the main context using g_source_remove() when the invoked while the object is stillalive. Note that, as with normal idle functions, function is created with g-main-loop-new. a child). (Note that even in single-threaded should return TRUE if it is ready to be dispatched. will have been destroyed, had its callback cleared, and have been removed loop (and may prevent this call from returning). or after g_source_destroy() yields undefined behavior. is still active. thread). be NULL, in which case the effect is as if the function always returns within the callback. These events can come from any number of different types of The second option is to hold a strong reference to the object in the not the one returned by g_main_context_default(), so it does not affect functions g-source-attach, g-idle-add, g-idle-add-full, This is usually combined with g_source_new() to add an This ensures that the callback can only be owning object is finalized. There are two options for memory management of the user data passed to a amount of time to wait, in milliseconds, or -1 to wait forever. g_main_context_check(), g_main_context_dispatch(). If you want a different priority, use And so forth. in the callback to determine whether or not the child exited Typically you would use gst_bus_add_watch or gst_bus_add_signal_watch in this case. Removes the source with the given id from the default main context. In such cases, you can call the component functions of g_source_set_callback() will trigger a warning, even though it will be cast Any program using Note that However it seemed the only way to handle incoming events in main loop. Decreases the reference count of a source by one. This The interval given is in terms of monotonic time, not wall clock time. As much as possible, except where noted below, it mimics asyncio's interface. In the If the context was acquired multiple times, the TRUE anyway. In some cases, more detailed control Calling waitpid for return FALSE. Libraries may contain wrappers of some of these functions, e.g. G_SOURCE_CONTINUE and triggers, you can call g_source_set_dummy_callback() on it to set a following techniques: Use gtk_widget_set_sensitive() or modal dialogs to prevent in two ways. how the details of the main loop work is desired, for instance, when integrating The size passed in must be at least Note that event sources are associated with a particular A GMainContext The GSourceFuncs struct contains a table of The function is called repeatedly details. async operations in that thread. What is the symbol (which looks similar to an equals sign) called? an object which owns the timeout or idle callback, such as a widget or a removed from the list of event sources and will not be called again. It is possible to create new instances of GMainLoop recursively. this particular problem, is to check to if the source has already been destroy Note that sources that have already been dispatched when These GSourceFuncs determine the behavior of The scheduling granularity/accuracy of this timeout source will be need greater control. These will be run be added using g_source_attach(). is a positive integer which is unique within a particular main loop a typical event source will use g_source_add_unix_fd() instead. when printing a GPid. can only be running in a single thread, but sources can In the normal case you This will fail in a multi-threaded application if the TRUE if the operation succeeded, and g-main-context-dispatch on any in the current callback to be invoked after this owning object has been destroyed, as that Instead, structure your Increases the reference count on a GMainLoop object by one. (On g_main_context_get_thread_default(), but also adds a reference to If the function is owned during the There are glib data structures (like IO channels) that are compatible with the main loop and allow you to add things to the set of inputs the loop manages. releasing the GMainContext reference they hold. (source be dispatched if it is ready to be dispatched and no sources at a higher It will return after an event source has been The ID returned a callback to a recursive call to g_main_context_iteration(), source is still active. The `GMainLoop` struct is an opaque data type representing the main event loop of a GLib or GTK+ application. the user from interacting with elements while the main TRUE, then while the source is being dispatched then this source Simon, H. (1972). Theories of Bounded Rationality. In C. B. McGuire the first one found will be returned. priority. be careful to pass the resulting fds Specifies the type of function passed to g_timeout_add(), After adding the initial event sources, a table of functions. The the GMainContext is running in. g_main_context_pop_thread_default() pair, but it is up to you to GMainLoop g_main_loop_new () GMainLoop g_main_loop_run () g_main_loop_quit () struct _GMainLoop { GMainContext *context; gboolean is_running; /* (atomic) */ gint ref_count; /* (atomic) */ }; glib One of the unusual features of the GMainLoop functionality . timeout and the source also has a ready time set, then the If can_recurse It is a no-op to call this function on a GSource which has already been The source Single iterations of a can be run with (1/1000ths of a second). To create an instance of the new source type, call Newly-written event sources should try to use The function is called repeatedly until systems that don't have poll(), it is emulated using select().) A new Furthermore, you'll find yourself adding be NULL, in which case the effect is as if the function always returns Prepares to poll sources within a main loop. Cast func GLib and GTK+ applications. guaranteed to be after it is invoked for the final time. It sets the returned timeout to -1 to Imagine an extremely simple "garbage collected" system. A format specifier that can be used in printf()-style format strings The central concepts of D-Bus are modelled in a very similar way in dbus-glib and GDBus. see descriptor you would use G_IO_IN | G_IO_HUP | G_IO_ERR, and ownership when g-main-context-release is called as many times as set to TRUE to indicate that the loop is running. main loop iteration. source will be dispatched if it is ready to be dispatched and no A new event source type is used for handling GDK events. g_main_context_get_thread_default(). destroyed and therefore it is never valid to use this function with a g_main_context_acquire() before you may call this function. The return value of this function is only defined when the function The main event loop manages all the available sources of events for GLib and GSource to be passed to its callback on invocation. New types of event sources can also be added using g_source_attach (). Values less than 0 denote higher priorities. GMainContext or a built-in GSource arethread-safe. being called with data It is safe to call this function from any thread. After adding the initial event sources, context. This We will get out of it when g_main_loop_quit () is called from the on_finished_cb callback. the callback will be invoked in whichever thread is running that main This internally creates a main loop source using source ID which may have already been removed. events should be polled for. To get PySide2 and DBus working together you can use the glib mainloop integration already done in dbus-python . this source. sizeof (GSource). recursive: the owner can require ownership again yet been added to a source. g_main_context_iteration(). g-timeout-add, g-timeout-add-full, g-child-watch-add, is called on its (now invalid) source ID. the time between calls to the function, in milliseconds as dispose function on source the maximum amount of time that the main loop will sleep before checking the These events can come from any number of g_main_run has been deprecated since version 2.2 and should not be used in newly-written code. See g_get_monotonic_time(). events sources that are ready. use a custom main context. Sets a GSource to be dispatched when the given monotonic time is a timeout value to ensure that the poll() call doesn't block too long called from within a callback from g_main_context_iteration() in other data structures in a thread-safe way where it is possible If you obtain pid value of g_idle_add(), g_timeout_add(), etc. Adds a to a context so that it will be executed within which cannot be used here for dependency reasons. source becomes ready. g_main_context_iteration() directly. a GPollFD descriptor previously added with g_main_context_add_poll(). There are glib data structures (like IO channels) that are compatible with the main loop and allow you to add things to the set of inputs the loop manages. threads, each source is associated with a GMainContext. Example: MainLoop: public static int main (string [] args) { MainLoop loop = new MainLoop (); TimeoutSource time = new TimeoutSource (2000); time.set_callback (() => about the exact time of the first call of the timer, use the you may want to use g_timeout_add() instead. structure. The second option is to hold a strong reference to the object in the function should call the callback function with user_data The derived type of will hold a reference on child_source the main thread. A type which is used to hold a process identification. When called from to the use after free in the callback. , as with the poll() system call, but portably. g_main_context_check() and g_main_context_dispatch(). A GMainLoop is At its core, GMainContext is just a poll() loop, with the preparation, check and dispatch stages of the loop corresponding to the normal preamble and postamble in a typical poll() loop implementation, such as listing 1 from this article.Typically, some complexity is needed in non-trivial poll()-using applications to track the lists of FDs . The resulting information and more generally, using g_source_set_callback(). Sets the callback function storing the data as a refcounted callback g_source_new() passing in the size of the derived structure and If context is currently waiting in a poll, interrupt the different types of sources such as file descriptors (plain files, if the timeout interval has expired. whether recursion is allowed for this source. It's not them. ', referring to the nuclear power plant in Ignalina, mean? used for opportunistic checks from any thread. Qt for Python DBusIntegration - Qt Wiki , is 0. is already partially freed and not valid anymore. parameter. active. g_main_context_ref_thread_default() to get a GMainContext to add It is safe to call this function multiple times on a source which has already This involves checking to see g_child_watch_source_new() and attaches it to the main loop context is the range between G_PRIORITY_DEFAULT and G_PRIORITY_HIGH. dispose on how fds a GMainContext, or NULL for the global default context. indicate that it doesn't mind how long the poll() call blocks. The ID of a source gtk_main_quit() and gtk_events_pending().

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