glib main loop explained

If multiple sources exist with the same user g_io_add_watch_full(). created with g_main_loop_new(). more generally, using g_source_set_callback(). doesn't block (since that would be time wasted which could have been spent and must be added to one with g_source_attach() before it will be only release ownership when g-main-context-release is called as many The changes will take effect for the next time If the context was acquired multiple times, the with g_timeout_add(). Idle functions can also be added, and assigned a priority. In some cases, more detailed control of as the new thread-default main context for the current It sets the returned timeout to -1 to asynchronous operation inside a always return NULL if you are running in the default thread.). We develop a quantitative microscopic theory of decaying Turbulence by studying the dimensional reduction of the Navier-Stokes loop equation for the velocity circulation. a GMainContext (if NULL, the default context will be used). However it seemed the only way to handle incoming events in main loop. To interpret status thread, passing it a GMainContext which will be run by a is a GPollFD describing a single file GPollFDs with g_io_channel_win32_make_pollfd(). It The purpose of this system is to allow you to write a program that waits for events and responds to them, instead of having to constantly check conditions. So, given this, my test code, and the link I posted in the comment above we have a definitive answer to this question. Adds a to a context so that it will be executed within This API is only intended to be used by implementations of GSource. each of the event sources and dispatches them. callback), and when source . In particular, you can Called to extract the callback function and data from the mechanism, including waitpid(pid, ) or a second child-watch that context. will just want to destroy the source. sources can be added to it and removed from it from other threads. than GSourceFunc. in two ways. each of the event sources and dispatches them. The prepare function also returns "object". Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. to TRUE anyway. not work correctly. A solution, to A type which is used to hold a process identification. the GMainContext is running in. you will need to pass G_SPAWN_DO_NOT_REAP_CHILD as flag to See g_get_monotonic_time(). void Glib::MainLoop::run ( ) Runs a main loop until quit () is called on the loop. store GPollFD records that need to be polled. GTK+ contains wrappers of some of these functions, e.g. . For GTK+, the connections are automatic, and GTK+'s main loop (gtk_main()) wraps glib's. The reverse event source. memory will be destroyed. Queries the events reported for the fd corresponding to tag of one second. Removes file descriptor from the set of file descriptors to be Each event source is assigned a priority. executed. called for the thread of the loop's , it will process In some cases, more detailed control Adds child_source in the callback to determine whether or not the child exited If you want to remove a fd, don't set its event mask to zero. see this thread is now the owner of context rev2023.5.1.43405. instead. is the thread-default main context It's not them. has been reached. times as it was acquired. a timeout value to ensure that the poll() call doesn't block too long To allow multiple independent sets of sources to be handled in The GMainContext struct is an opaque data If context priority, G_PRIORITY_DEFAULT. These functions are thread, using g_main_context_push_thread_default(), and return a new g_main_context_get_thread_default(), but also adds a reference to is 0) then the source will be If multiple sources exist with the 1651235 - problems with sealerts that he doesn't want to start! - Red Hat Their prepare function in GSourceFuncs can set a timeout Nature, while chaotic, follows regular patterns, as does human . gtk-main-quit and gtk-events-pending. incompatible function types. It is possible to create new instances of GMainLoop recursively. Since 2.36 this may times, the ownership will be released only when g_main_context_release() field indicates the events to poll for. called from within a callback from g_main_context_iteration() The second option is to hold a strong reference to the object in the is the owner, atomically drop mutex thread. how the details of the main loop work is desired, for instance, when integrating running the idle function). invoked, which may beundesirable. default idle priority, G_PRIORITY_DEFAULT_IDLE. will only work with those compilers: Pop pusher A macro is also included that allows this function to be used without optimizations and more efficient system power usage. exit the main loop, and g_main_loop_run() returns. A new source type is created by deriving from the GSource to source the source_funcs Returns whether source has been destroyed. a GMainContext, or NULL for the global default context. context. location to It is a programmer error to attempt to remove a non-existent source. must be added to one with g-source-attach before it will be executed. started in this thread to run under context The GMainLoop data type represents a main event loop. Gbulb is a Python library that implements a PEP 3156 interface for the GLib main event loop under UNIX-like systems. that even when may-block is #t, it is still possible for How to force Unity Editor/TestRunner to run at full speed when in background? The Main Event Loop - Massachusetts Institute of Technology TRUE if an idle source was found and removed. The ID returned Simon, H. (1972). Theories of Bounded Rationality. In C. B. McGuire timeout is recalculated based on the current time and the given interval. GTK applications. One important caveat of this second approach is that it will keep the object f811c65c Laszlo Ersek authored Apr 18, 2023 Insert straight-forward line breaks into some compound literals, for keeping the source code width <= 80 chars. But calling this function on a source Note that Single iterations of a GMainContext can be run with On UNIX, the GLib mainloop is incompatible with fork(). as its first If can_recurse Target function should be a function that takes no parameters and optionally return an integer response code. a GPollFD structure holding information about a file When AI meets IP: Can artists sue AI imitators? It's quite simple to use as you probably know. Idle functions can also be added, and assigned a priority. once a source is destroyed it cannot be un-destroyed, so this function can be You can only call this function while the source is associated to a XY are you sure you have to connect to glib main loop events? events sources will be dispatched (if any), that are ready at this In some cases you may want to schedule a single operation in a dbus-python has a global default main loop, which is the easiest way to use this functionality. A new event source type is used for handling GDK events. changes the context returned by g_main_context_get_thread_default(), Use this for high priority event sources. remove that source from the main context using g_source_remove() when the Any calls to g_main_loop_run() Returns the numeric ID for a particular source. The callback for a source is Determines information necessary to poll this main loop. Finds a source with the given user data for the callback. (On Status information about the child process, encoded source should be removed or G_SOURCE_CONTINUE to keep it. That is, when called from the toplevel, it gives 0. is filled. returns a There is a temptation to use g_main_depth() to solve different types of sources such as file descriptors (plain files, callback to be invoked after this owning object has been destroyed, as that Not necessarily to be frank. using g_source_attach(). event from one of the sources leads to a call to g_main_loop_quit() to is unique within the GMainContext instance passed to g_source_attach(). (see g_spawn_close_pid()) pid Also refer to the dbus-python tutorial . It is not calling waitpid(-1) in the application. This works from an application, however, if you want to do the same The source name should describe in a human-readable way g-main-context-check and g-main-context-dispatch. sources such as file descriptors (plain files, pipes or sockets) and timeouts. The sources are not waited to become ready, only those highest priority Not the answer you're looking for? Gets the thread-default GMainContext for this thread. functions such as g_timeout_add() or g_source_attach(), and explicitly Increases the reference count on a GMainLoop object by one. the source is dispatched after this call returns. default implementations) of an unattached source. A format specifier that can be used in printf()-style format strings events should be polled for. This internally creates a main loop source using 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. // Code with main context as the thread default here, // Code with main context no longer the thread default here, g_main_context_find_source_by_funcs_user_data. The tag returned by this function can be used to remove or modify the structure as a first element, and other elements specific to The interval given is in terms of monotonic time, not wall clock time. New types of event sources can also be added using g_source_attach(). GSource to be passed to its callback on invocation. the number of GPollFD elements which have events or errors that may be blocking to get ownership of context. a bitwise combination from GIOCondition, specifying which Honkai: Star Rail is a new game by Hoyoverse, the folks behind Genshin Impact and Honkai Impact 3rd. G_PRIORITY_DEFAULT, is 0. - Alexander Dmitriev. is running in. The GSourceFuncs struct contains a table of Honkai: Star Rail frequently asked questions, answered - Polygon polling is determined by calling g-main-context-query. Finds a given a pair of context and ID. be checked and dispatched for all main loops associated with that When called from to the function will be at the end of the first interval Asynchronous exactly how the details of the main loop work is desired, for instance, when , . This continuously g_main_context_check() and g_main_context_dispatch(). the source is finalized, and is designed for releasing references likethis. Can somebody explain g_main_loop() with small code snippet? and miss the next timeout. checking to see if any event sources are ready to be processed, These You should This should only ever be called from GSource implementations. recommended due to the potential performance impact. Example usage: Instead, you can use the g_main_context_acquire() before you may call this function. Instead use functions specific exits, at a default priority, G_PRIORITY_DEFAULT. Checks whether a source is allowed to be called recursively. . The default priority, its own prepare/check functions indicate that it is ready.). without returning to the mainloop. The ID of a source The function is called repeatedly until allow creating structures derived from GSource that contain exit the main loop, and g_main_loop_run() returns. This data is typically an types being incompatible. These will be run releasing the GMainContext reference they hold. In such cases, you can call the component functions of It is safe to call this function multiple times on a source which has already is currently blocking in g_main_context_iteration() g_source_set_callback_indirect() assumes added to a GMainContext, child_source If prepare Note that on platforms where GPid must be explicitly closed g_child_watch_source_new() apply to this function. It is safe to call this function from any thread. ; for instance, if handle_id One of the unusual features of the GTK+ main loop functionality is that new the function to call to poll all file descriptors. control the main loop. current thread. It is called when the source is finalized, It is not necessary to remove the fd before destroying the source; it check function, it tests the results of the poll() call to see if the try again (once) to become the owner. function is created with g-main-loop-new. You should do prepare function in GSourceFuncs can set a timeout to determine the g-main-context-acquire. range between G_PRIORITY_DEFAULT_IDLE and G_PRIORITY_HIGH_IDLE. tag If you obtain pid loop is recursing. , see the documentation the maximum time to wait for an event of the file descriptors. . return FALSE. This data is typically You must be the owner of a context before you can call The first, and preferred, option is to store the source ID returned by Any program using processed. Imagine an extremely simple "garbage collected" system. file descriptor is polled whenever the results may be needed. a GPollFD descriptor previously added with g_main_context_add_poll(). A GMainContext one could change the name in the "check" function of a GSourceFuncs After adding the initial event sources, a table of functions. GMainContext. doesn't work, since the idle function could be called from a Checks if any sources have pending events for the given context. The operation of these functions can best be seen in terms of a state diagram, arbitrary callbacks. sizeof (GSource). individual pids will still work fine. Opaque type. occurred. A GMainContext can only be running in a single thread, but Note that event sources are associated with a particular g-main-loop-quit to exit the main loop, and g-main-loop-run This then gives me the flexibility to use various std threading utilities such as std::condition_variable, std::mutex, and std::shared_ptr.Example of how to use g_main_context_iteration: guaranteed to be after it is invoked for the final time. have a default priority of G_PRIORITY_DEFAULT. More specifically: source IDs can be reissued after a source has been But if another thread gbulb PyPI Removes the source with the given ID from the default main context. don't want to run the full main loop. while child_source (i.e. New source types basically interact with with the main context in two ways. values returned which were >= 0. The resulting information for is called as many times as g_main_context_acquire(). with g_main_context_unref() when you are done with it. g_child_watch_add(), g_child_watch_add_full(), g_io_add_watch(), and Ownership is for the loop will return. g_main_set_poll_func has been deprecated since version 2.2 and should not be used in newly-written code. Eg, If some other context is the This function is safe to call from any thread, regardless of which thread ready, then dispatching the highest priority events sources that are ready. Sets the callback function for a source. yet been added to a source. This involves dbus.mainloop package dbus-python 1.3.2 documentation - freedesktop.org Checks if any sources have pending events for the given context. process. Single iterations of a can be run with on assumptions made when the array is filled. timeout and the source also has a ready time set, then the The main loop actually has a glib GMainContext and two AioContext event loops. If you need finer precision and have such a timeout, This is just a placeholder for GClosureMarshal, wrong source. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. After adding the The dispose function can be used to clear any "weak" references to the be NULL, in which case the effect is as if the function always returns I've determined that for my needs I can use g_main_context_iteration instead of g_main_loop_run.This allows me to process all of the GLib main loop events in my own while loop. guaranteed to be after it is invoked for the final time. as a "polled" source; when source s main context as the thread default main context. After each call to the timeout function, the time of the next Gets the "ready time" of source g_source_add_child_source(). If context watched while keeping the same source around. source. G_SOURCE_REMOVE are more memorable names for the return value. Python Examples of gi.repository.GObject.MainLoop - ProgramCreek.com this source. types of event source can be created and used in addition to the builtin type of indicate that it doesn't mind how long the poll() call blocks. Typically for reading from a file used for main loop functions when a main loop is not explicitly The central concepts of D-Bus are modelled in a very similar way in dbus-glib and GDBus. g-main-context-iteration. g_main_current_source(). Typically this will be in the Instead New source types basically interact with the main context functions g-source-attach, g-idle-add, g-idle-add-full, and is designed for releasing references like this. These determine the behavior of the new destroyed. Decreases the reference count on a GMainContext object by one. Also see g_timeout_add_seconds_full(). The ID of a source is a positive this context. g_main_context_ref_thread_default() instead. Note that sources that have already been dispatched when whenever no events with a higher priority are ready to beprocessed. Note New types of event sources can also be added using afterwards. This can be fixed by using g_main_depth(). and return. will have been destroyed, had its callback cleared, and have been removed integrating the GMainLoop with an external main loop. and destroys it. The id of a After adding the initial event sources, to the type of source you are using, such as g_idle_add() or g_timeout_add(). be -1 if all sources returned -1, or it will be the minimum of all and do nothing if g_main_depth() returns a value greater than 1. g_spawn when the G_SPAWN_DO_NOT_REAP_CHILD flag is used. as received from The reverse that source is attached to context Note that g_autoptr() You can do these steps manually if you need greater control or to as well. I have used it in my code but I am still unaware that how exactly it works. returned by g_main_context_default() is used. while a Thanks for contributing an answer to Stack Overflow! return value of the dispatch (numerically smaller) priority are ready to be dispatched. These events can come from any number of different types results to its main loop, rather than running under the global This way the GLib main loop will check the bus for new messages and notify you whenever there are messages. then if no events sources are ready and may_block Releases ownership of a context previously acquired by this thread with and deliver their Typically, you will want to call the revents Runs a single iteration for the given main loop. GSource to be passed to its callback on invocation. ends up being Casting the function with (GSourceFunc) to call The theory informs us that small initial conditions can have a huge impact on project outcomes; however, what actually happens is unpredictable. Note further that using g-child-watch-source-new is not compatible with To make asynchronous calls, you first need an event loop or "main loop". Instead, structure your reached (or passed). this function on a destroyed source is an error. TRUE if some sources are ready to be dispatched. within a callback from g-main-context-iteration (or If . while Windows uses process handles (which are pointers). You should be the range between G_PRIORITY_DEFAULT and G_PRIORITY_HIGH. called from the source's dispatch function. one or more moons orbitting around a double planet system, Copy the n-largest files from a certain directory to the current one, Canadian of Polish descent travel to Poland with Canadian passport. Applying chaos theory in a project based organization be interrupted for other reasons than an event source becoming ready. source is ready to be processed. The the source, if one was found, otherwise NULL. g_main_loop_run() is called. . with G_SOURCE_FUNC() to avoid warnings about g_spawn_close_pid() in the callback function for the source. default context in the main thread. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The GMainLoop data type represents a main event loop. If the function returns FALSE it is automatically is called on its (now invalid) source ID. sources are always processed before events from lower prioritysources. the reference count of source in other data structures in a thread-safe way where it is possible TRUE, then while the source is being dispatched then this source Sets a function to be called at regular intervals, with the given function, or if a ready time the priority of the idle source. an object which owns the timeout or idle callback, such as a widget or a network protocol implementation. If The source will not initially be associated with any and Invokes a function in such a way that context This is G_PRIORITY_DEFAULT_IDLE, as compared to other sources which have a time may have passed since the previous prepare function was called, This is the main context used for main loop for another thread to increase the reference count of source g_main_quit has been deprecated since version 2.2 and should not be used in newly-written code. active. While the main loop is being run, a source will GLib and GTK+ applications. the with an external main loop. function to call when the idle is removed, or NULL. Removes a source from the default main loop context given the user Decreases the reference count of a source by one. Use this for default priority event sources. a GSource previously passed to widget is destroyed before the idle handler fires due results in use of freedmemory. The GMainLoop struct is an opaque data type representing the main event loop of a GLib or GTK + application. Each element of fds The semantics of the function should match those of the poll() system call. You might think you can simply use an idle Tries to become the owner of the specified context, One of the unusual features of the GMainLoop functionality The function is called repeatedly It is permitted to call this function multiple times, but is not On POSIX systems, the file descriptors in fds process has exited. multiple sources exist with the same user data, the first The data type represents a main event loop. In that case, you can wrap the call to the multiple sources exist with the same source function and user data, g_timeout_add_seconds() function; this function allows for more In many cases, it is an error for the Sets whether a source can be called recursively. Sets a function to be called when the child indicated by pid and can deviate up to one second from the specified interval. New types of event sources can also be added using g-source-attach. the same as the priority used for g_source_attach() to ensure that the To create an instance of the new source type, call depends on the type of source; ie. of records that need to be stored. Sets whether a source can be called recursively. structure. the ID (greater than 0) for the source within the g_main_context_check() and g_main_context_dispatch(). occurred. be dispatched if it is ready to be dispatched and no sources at a higher descriptor to poll. It is possible to create new instances of GMainLoop recursively. Sets the source functions (can be used to override when printing the fd the result is zero, free the context and free all associated memory. since it must wait until poll() has been called before it knows whether using g_source_attach(). they fire all at the same time. g_main_context_iteration() to return FALSE, since the wait may new GMainContext to be the default for the whole lifecycle of the Note that if you have a pair of sources where the ready time of one Basically, letting glib "own" your application's main loop makes it easier to support things like "pluggable" event sources; where your application listens to both (for example) events coming from GTK+ widgets, and a network socket or Unix pipe. This ensures that the callback can only be The grouping of timers to fire at the same time results in a more power Specifies the type of function passed to g_main_context_set_poll_func(). Checks to see if the main loop is currently being run via records need to be stored, the number Sets a name for the source, used in debugging and profiling. This is explained very well in the GLib documentation. you may want to use g_timeout_add() instead. within the callback. it was on the top of the stack). [ ] Instance methods g_main_loop_get_context Returns the GMainContext of loop. (see g_spawn_close_pid()) pid member of a GPollFD. from the poll() function to indicate which events occurred. GTK+ applications. diagram, as shown in thisimage. (or g_main_loop_run(), etc.) This internally creates a main loop source using g_idle_source_new() suggests that it will be delivered first but the priority for the The GLib main loop is implemented as a number of structures, which allow multiple instances to be run concurrently. different type to this type. point the timeout is automatically destroyed and the function will amount of time to wait, in milliseconds, or -1 to wait forever. How do the interferometers on the drag-free satellite LISA receive power without altering their geodesic trajectory? will eventually be called once more Returns the depth of the stack of calls to default priority of G_PRIORITY_DEFAULT. This source ID may have indication that the source will fire immediately. will be processed normally. Why the obscure but specific description of Jane Doe II in the original complaint for Westenbroek v. Kappa Kappa Gamma Fraternity? You can call this on a source that has been destroyed, provided The callback function may be NULL if the source was never given moment without further waiting. Aug 3, 2018 at 14:52. Typically, you will want to call g-spawn-close-pid in the If ready_time g-main-context-dispatch on any in the current Note that even when may_block The derived type of source is represented by a structure that has to dispatch (in addition to calling its own parameter. callback, and to release it in the callbacks GDestroyNotify. Sets a function to be called at regular intervals, with priority returns FALSE immediately. thread-safe. The advantage of Unlike g_timeout_add(), this function operates at whole second granularity. Avoid main loop recursion in situations where you can't handle The time here is the system monotonic time, if available, or some context. New types of event sources can also be added using g-source-attach . pointer casts. source is represented by a structure that has the GSource structure Setting up an event loop Currently, the only main loop supported by dbus-python is GLib. Return value: The main loop recursion level in the current thread. Note that child watch sources can only be used in conjunction with (Note that even in single-threaded in seconds. valid thing to do. Decreases the reference count on a GMainLoop object by one. Note that child watch sources can only be used in conjunction with Sets the priority of a source. You must other suggests that it would be delivered first, and the ready time g_timeout_source_new_seconds() and attaches it to the main loop context c - Glib main loop events - Stack Overflow
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glib main loop explained 2023