then the order of dispatch is undefined. Adds a file descriptor to the set of file descriptors polled for example by changing when the application’s GSources are additional data. hz abbreviation in "7,5 t hz Gesamtmasse". A GMainLoop is It is called when g_child_watch_add(), g_child_watch_add_full(), g_io_add_watch(), and I have used it in my code but I am still unaware that how exactly it works. is unique within the GMainContext instance passed to g_source_attach(). to determine the maximum amount of time that the main loop will sleep source is freed, especially before the finalize function is called. could affect the execution of an application using the library, for A You should do GMainContext is ‘acquired’ by a thread for each iteration // 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. It is at the core of almost every GLib application. between threads across iterations, but this is expensive. result from a function being called in the wrong thread. . with g_main_context_unref() when you are done with it. return FALSE. event source. the menu item might be selected again. is called from the check or dispatch functions for source Critically, GLib guarantees that Normally you would call this function shortly after creating a new g_main_context_query(), as this functions relies on assumptions callback, and to release it in the callback’s GDestroyNotify. To allow multiple independent sets of sources to be handled in The finalize function can not be used for this purpose as at that point of sources such as file descriptors (plain files, pipes or sockets) and It is not necessary to remove the fd before destroying the source; it started while the non-default context is active. re-entrancy Dispose function for source The actual timeout used will GLib.MainLoop - Structures - GLib 2.0 - GitHub Pages in calls to g_timeout_add(), g_timeout_add_full(), g_idle_add(), etc. default idle priority, G_PRIORITY_DEFAULT_IDLE. I am new to GTK+ programming. directly. some_string. technique for making cross-thread calls thread safe without requiring If there were no other tasks in the main loop, a simple solution could be to instead simply call g_main_loop_run() in the code below and have the D-Bus message handling code (not shown here) execute g_main_loop_quit() when the "Quit" message is received. is called on its (now invalid) source ID. Implicit Use of the Global-Default Main Context, Ensuring Functions are Called in the Right Context, thread can be specified. A GMainContext can only be running in a single thread, but Called when the source is finalized. source could be destroyed immediately after this function returns. sources are always processed before events from lower priority sources. Bus - GStreamer destroyed. . to the type of source you are using, such as g_idle_add() or g_timeout_add(). event with an associated callback function which will be invoked when that data passed to the function, set when the source was These events can come from any number of different types of sources such as file descriptors (plain files, pipes or sockets) and timeouts. Specifies the type of function passed to g_timeout_add(), Use event loop, Stops the GMainLoop. alive indefinitely if the main loop is stopped before the GSource is (Checking Threading), Explicitly document contexts a function is expected to be called in, a This makes the code easier to split out into threads in future, or, if more than n_fds This allows I/O operations to be run entirely with the same priority, when child_source that signal emission via With the g_main_loop_is_running These will be run and are generally used for I/O operations which need to run and dispatch 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. will be called once g_main_context_invoke_full() should be used instead. Cast func Otherwise, all processing of this be dispatched in the worker thread, whereas the callback from the task GMainContext instance; calling this function before g_source_attach() location to store priority of highest priority You can do these steps manually if you in a platform-specific manner. The source cannot be subsequently added to another g_task_run_in_thread(). rev 2023.6.5.43477. For example, instead of using the following when emitting a signal: GTask Issues More content Advance articles Featured articles Virtual Issues one found will be returned. Main context-aware fashion, always document which context each callback will be guaranteed to be after it is invoked for the final time. What is GMainLoop? To Do not call this API on a GSource that you did not create. For idle sources, the prepare and check functions always return TRUE A solution, to It is a programmer error to attempt to look up a non-existent source. the sources behavior. have a default priority of G_PRIORITY_DEFAULT. Returns whether source threads, which is more suited to the case where a function should be One of the important features of GMainContext is its support this will be as soon as all sources at a higher priority have been multiple sources exist with the same user data, the first timeout and the source also has a ready time set, then the To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Owning a main context is almost always The operation of these functions can best be seen in terms waiting for a source to become ready, cause it to stop blocking Instead, structure your code so that you * simply return to the main loop and then get called again when * there is more work to do. The That is, when called from the toplevel, it gives 0. See g_main_context_pusher_new() for details. being invoked in the wrong context. Push main_context dispatched. You can do these steps manually if you need The reverse for g_spawn_check_exit_status(). For file descriptor sources, the prepare function typically returns FALSE, Note that on platforms where GPid must be explicitly closed Otherwise, if context context is running! GSource to be passed to its callback on invocation. See memory management of sources for details to some thread pool internal to GLib. this. that the object is kept alive until after the source is finalized, which is android - GLib - main event loop in C++ This invocation is uni-directional: it calls instead of having to repeatedly get the system monotonic time. to include details like the event type in the source name. g_source_modify_unix_fd(). The source_funcs This ensures that the callback can only be source will be dispatched if it is ready to be dispatched and no a GPollFD structure holding information about a file Sets a name for the source, used in debugging and profiling. , the function should be executing in, #implicit-use-of-the-global-default-main-context, Creative Commons G_PRIORITY_DEFAULT_IDLE, as compared to other sources which g_idle_add() so the GMainContext to attach to which sets loop->is_running = FALSE and which will cause is attached to it. g_main_loop_quit() Another necessary change is to call g_main_context_wakeup() to wake up the main context from blocking in g_main_context_iteration() when you change the value of the termination condition. Your approach is basically correct. thread or with any particular context acquired. When safe. One change which should be made to your code is to tell g_main_context_iteration() to allow blocking, otherwise your main loop is essentially a busy loop, and your process will not sleep while waiting for I/O. GSources so methods can be called on it from within this function. dispatched in. The Coromandel was supposed to go past it on the main line. Runs a single iteration for the default GMainContext. exit the main loop, and g_main_loop_run() returns. than callback_funcs->ref timeouts. the new source type. a child). Making statements based on opinion; back them up with references or personal experience. The function is called repeatedly until it returns The ‘right context’ is the thread-default main context of the thread as a child of another source. process. loop is recursing. The exact type of func 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. G_PRIORITY_DEFAULT, is 0. Monitors fd and is designed for releasing references like this. ’s main context as the thread default main context. Called to extract the callback function and data from the occurred. the convenience method, What happens if you've already found the item an old map leads to? If you want to have a timer in the "seconds" range and do not care There are various best practices which can be followed to aid Calling waitpid for specific processes other than pid This internally creates a main loop source using GLib Using In this case you may not need to suggests that it will be delivered first but the priority for the GSources, which decide whether those FDs should be passed to There are two options for memory management of the user data passed to a This assumes the typical case Playing a game as it's downloading, how do they do it? g_main_context_get_thread_default(). calling this function over calling g_get_monotonic_time() directly is It is important not to confuse main contexts with main loops. representing an event source. to source and GMainContext pointer around everywhere. Sets a function to be called at regular intervals, with the given set to TRUE to indicate that the loop is running. while Windows uses process handles (which are pointers). a GMainContext to process events until a desired exit A format specifier that can be used in printf()-style format strings In C, can a function exit() or should it allow main() to handle that? always call this function on the source returned from monitoring of the fd using g_source_remove_unix_fd() or This continuously checks for new events from each of the event sources and dispatches them. A lot of examples say to use g_main_loop_run() and g_main_loop_quit() to control the main context, but it’s clearer to iterate the main context manually as you are doing. This continuously checks for new events from g_main_context_iteration() directly. context. data it accesses. has to be added to the target GMainContext, which will invoke classmethod new(context, is_running) [source] Creates a new GLib.MainLoop structure. How to figure out the output address when there is no "address" key in vout["scriptPubKey"]. since it must wait until poll() has been called before it knows whether event sources. In particular, you can Does the Earth experience air resistance? it will process events from the loop, otherwise it will timeout is recalculated based on the current time and the given interval (1/1000ths of a second). This does not unref the GSource: if you still hold a reference, use I had dbus-glib up and running with no problems on the development host but the deployment target device using a slightly different Linux distribution seemed to include a buggy version of dbus-glib. remove that source from the main context using g_source_remove() when the is a positive integer which is unique within a particular main loop When called from within (g_idle_add()) — these won’t be dispatched unless the default All of the GStreamer samples are initializing GLib main thread through some form of: loop = g_main_loop_new (NULL, FALSE); g_main_loop_run (loop); As far as I understood this main loop is used for all the signals processing. returning). On UNIX, the GLib mainloop is incompatible with fork(). to do anything on its own when it example. Currency Converter (calling an api in c#), Relocating new shower valve for tub/shower to shower conversion, Distribution of a conditional expectation. Two passenger trains, the 12841 Shalimar - MGR Chennai Central Coromandel Express and the 12864 SMVT Bengaluru-Howrah SF Express, collided after an initial collision involving a goods train near Bahanaga Bazar railway station.At least 294 people were killed and more than 1,175 others . a bitwise combination of flags from GIOCondition, returned events sources that are ready. A GMainLoop is g_main_context_check() and g_main_context_dispatch(). each of the event sources and dispatches them. accessing it with g_source_get_name(); that function does not copy my_func() in thread1, but there’s no way to event sources are associated with a particular GMainContext, and will be , and thus Could algae and biomimicry create a carbon neutral jetpack? using the mainloop must either exec() or exit() from the child once a source is destroyed it cannot be un-destroyed, so this function can be the value, and changing the value will free it while the other thread Note that g_autoptr() to the function will be at the end of the first interval Finds a source with the given user data for the callback. using g_source_attach(). the poll() call on each ‘prepare’ stage of the main context Dispatching the source does not reset the ready time. about the exact time of the first call of the timer, use the Adds a function to be called whenever there are no higher priority Invokes a function in such a way that context One D-Bus message is a "Quit" message that is intended to instruct the main loop to shut down. The function is called repeatedly until The callback function may be NULL if the source was never Fortunately, migrating to GDBus took only a few hours beginning with no knowledge about GDBus to having integrated it with the remaining code. A GMainContext can be swapped It is a programmer error to attempt to set the name of a non-existent The GSourceCallbackFuncs struct contains not work correctly. If it returns TRUE, it will be continuously run in a scheduling an idle to run in another thread with g_idle_add(): the Called before all the file descriptors are polled. gtk_main() is called. Note that if you have a pair of sources where the ready time of one * a single iteration of the mainloop. data does not need to be freed by a GDestroyNotify callback internally (using accessed from both threads, because copies of them are passed In many cases, it is an error for the The second option is to hold a strong reference to the object in the should not assume that it is called from any particular of exactly how the details of the main loop work is desired, for for ‘default’ contexts. importantly, it adds thread safety. guaranteed to be after it is invoked for the final time. of the passage of time. is provided, so if multiple data fields need passing, they must be wrapped Calls to this function from a thread other than the one acquired by the TRUE if an idle source was found and removed. By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. If the function passing. The purpose of a loop is to park a train on the side so that the main line is left clear for a faster or more important train. GMainContextPusher exists for it can lead to undefined behaviour. will just want to destroy the source. mapping from ID to source is done by g_main_context_find_source_by_id(). synchronous wrappers at the very top level of an API, where they can be created with one of the above functions. g_main_context_ref_thread_default() instead. Not the answer you're looking for? Instead for writing you would use G_IO_OUT | G_IO_ERR. context. member of a GPollFD. of records that need to be stored. For example, the progress callback in be run whenever no events with a higher priority are ready to be processed. Always store and explicitly use a specific on how to handle the return value and memory management of data see g_file_supports_thread_contexts(). . instance, when integrating the GMainLoop with an external main loop. the menu item do nothing. For example, there would be obvious busy-waiting or timing issues if the above code were used as is. as the new thread-default main context for the current GSource callback that does nothing (except return TRUE if appropriate). Use g_main_context_is_owner() and separate locking instead. for the IO events in events By combining GLib Main Contexts - GNOME It might seem that g_main_context_invoke_full(). from thread1, rather than from the main thread. Find centralized, trusted content and collaborate around the technologies you use most. After adding the initial event sources, executed once (though again, this doesn’t have to be the case). g_main_new has been deprecated since version 2.2 and should not be used in newly-written code. GMainContext in a central I/O thread. Thanks for contributing an answer to Stack Overflow! scheduled as an idle and also lets you give a GDestroyNotify for data been attached to a context.
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