### Method

# GLib MainContext push_thread_default

since: 2.22

#### Declaration

    void
    g_main_context_push_thread_default (
      GMainContext* context
    )

#### Description

Acquires `context` and sets it as the thread-default context for the current thread. This will cause certain asynchronous operations (such as most [gio][gio]-based I/O) which are started in this thread to run under `context` and deliver their results to its main loop, rather than running under the global default main context in the main thread. Note that calling this function changes the context returned by g_main_context_get_thread_default(), not the one returned by g_main_context_default(), so it does not affect the context used by functions like g_idle_add().

Normally you would call this function shortly after creating a new thread, passing it a `GMainContext` which will be run by a `GMainLoop` in that thread, to set a new default context for all async operations in that thread. In this case you may not need to ever call g_main_context_pop_thread_default(), assuming you want the new `GMainContext` to be the default for the whole lifecycle of the thread.

If you don’t have control over how the new thread was created (e.g. in the new thread isn’t newly created, or if the thread life cycle is managed by a `GThreadPool`), it is always suggested to wrap the logic that needs to use the new `GMainContext` inside a `g_main_context_push_thread_default()` / `g_main_context_pop_thread_default()` pair, otherwise threads that are re-used will end up never explicitly releasing the `GMainContext` reference they hold.

In some cases you may want to schedule a single operation in a non-default context, or temporarily use a non-default context in the main thread. In that case, you can wrap the call to the asynchronous operation inside a `g_main_context_push_thread_default()` / `g_main_context_pop_thread_default()` pair, but it is up to you to ensure that no other asynchronous operations accidentally get started while the non-default context is active.

Beware that libraries that predate this function may not correctly handle being used from a thread with a thread-default context. Eg, see g_file_supports_thread_contexts().

Available since: 2.22