glib/main_context.rs
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// Take a look at the license at the top of the repository in the LICENSE file.
use std::mem;
use crate::ffi::{self, gboolean, gpointer};
use crate::{source::Priority, translate::*, MainContext, Source, SourceId};
impl MainContext {
/// Prepares to poll sources within a main loop. The resulting information
/// for polling is determined by calling `GLib::MainContext::query()`.
///
/// You must have successfully acquired the context with
/// [`acquire()`][Self::acquire()] before you may call this function.
///
/// # Returns
///
/// [`true`] if some source is ready to be dispatched
/// prior to polling.
///
/// ## `priority`
/// location to store priority of highest priority
/// source already ready.
#[doc(alias = "g_main_context_prepare")]
pub fn prepare(&self) -> (bool, i32) {
unsafe {
let mut priority = mem::MaybeUninit::uninit();
let res = from_glib(ffi::g_main_context_prepare(
self.to_glib_none().0,
priority.as_mut_ptr(),
));
let priority = priority.assume_init();
(res, priority)
}
}
/// Finds a #GSource given a pair of context and ID.
///
/// It is a programmer error to attempt to look up a non-existent source.
///
/// More specifically: source IDs can be reissued after a source has been
/// destroyed and therefore it is never valid to use this function with a
/// source ID which may have already been removed. An example is when
/// scheduling an idle to run in another thread with `idle_add()`: the
/// idle may already have run and been removed by the time this function
/// is called on its (now invalid) source ID. This source ID may have
/// been reissued, leading to the operation being performed against the
/// wrong source.
/// ## `source_id`
/// the source ID, as returned by `GLib::Source::get_id()`.
///
/// # Returns
///
/// the #GSource
#[doc(alias = "g_main_context_find_source_by_id")]
pub fn find_source_by_id(&self, source_id: &SourceId) -> Option<Source> {
unsafe {
from_glib_none(ffi::g_main_context_find_source_by_id(
self.to_glib_none().0,
source_id.as_raw(),
))
}
}
// rustdoc-stripper-ignore-next
/// Invokes `func` on the main context.
///
/// If the current thread is the owner of the main context or the main context currently has no
/// owner then `func` will be called directly from inside this function. If this behaviour is
/// not desired and `func` should always be called asynchronously then use [`MainContext::spawn`]
/// [`glib::idle_add`](crate::idle_add) instead.
// rustdoc-stripper-ignore-next-stop
/// Invokes a function in such a way that @self is owned during the
/// invocation of @function.
///
/// If @self is [`None`] then the global-default main context — as
/// returned by [`default()`][Self::default()] — is used.
///
/// If @self is owned by the current thread, @function is called
/// directly. Otherwise, if @self is the thread-default main context
/// of the current thread and [`acquire()`][Self::acquire()] succeeds, then
/// @function is called and [`release()`][Self::release()] is called
/// afterwards.
///
/// In any other case, an idle source is created to call @function and
/// that source is attached to @self (presumably to be run in another
/// thread). The idle source is attached with `GLib::PRIORITY_DEFAULT`
/// priority. If you want a different priority, use
/// [`invoke_full()`][Self::invoke_full()].
///
/// Note that, as with normal idle functions, @function should probably
/// return [`false`]. If it returns [`true`], it will be continuously run in a
/// loop (and may prevent this call from returning).
/// ## `function`
/// function to call
#[doc(alias = "g_main_context_invoke")]
pub fn invoke<F>(&self, func: F)
where
F: FnOnce() + Send + 'static,
{
self.invoke_with_priority(crate::Priority::DEFAULT_IDLE, func);
}
// rustdoc-stripper-ignore-next
/// Invokes `func` on the main context with the given priority.
///
/// If the current thread is the owner of the main context or the main context currently has no
/// owner then `func` will be called directly from inside this function. If this behaviour is
/// not desired and `func` should always be called asynchronously then use [`MainContext::spawn`]
/// [`glib::idle_add`](crate::idle_add) instead.
#[doc(alias = "g_main_context_invoke_full")]
pub fn invoke_with_priority<F>(&self, priority: Priority, func: F)
where
F: FnOnce() + Send + 'static,
{
unsafe {
self.invoke_unsafe(priority, func);
}
}
// rustdoc-stripper-ignore-next
/// Invokes `func` on the main context.
///
/// Different to `invoke()`, this does not require `func` to be
/// `Send` but can only be called from the thread that owns the main context.
///
/// This function panics if called from a different thread than the one that
/// owns the main context.
///
/// Note that this effectively means that `func` is called directly from inside this function
/// or otherwise panics immediately. If this behaviour is not desired and `func` should always
/// be called asynchronously then use [`MainContext::spawn_local`]
/// [`glib::idle_add_local`](crate::idle_add_local) instead.
pub fn invoke_local<F>(&self, func: F)
where
F: FnOnce() + 'static,
{
self.invoke_local_with_priority(crate::Priority::DEFAULT_IDLE, func);
}
// rustdoc-stripper-ignore-next
/// Invokes `func` on the main context with the given priority.
///
/// Different to `invoke_with_priority()`, this does not require `func` to be
/// `Send` but can only be called from the thread that owns the main context.
///
/// This function panics if called from a different thread than the one that
/// owns the main context.
///
/// Note that this effectively means that `func` is called directly from inside this function
/// or otherwise panics immediately. If this behaviour is not desired and `func` should always
/// be called asynchronously then use [`MainContext::spawn_local`]
/// [`glib::idle_add_local`](crate::idle_add_local) instead.
#[allow(clippy::if_same_then_else)]
pub fn invoke_local_with_priority<F>(&self, _priority: Priority, func: F)
where
F: FnOnce() + 'static,
{
// Checks from `g_main_context_invoke_full()`
// FIXME: Combine the first two cases somehow
if self.is_owner() {
func();
} else if let Ok(_acquire) = self.acquire() {
func();
} else {
panic!("Must be called from a thread that owns the main context");
}
}
unsafe fn invoke_unsafe<F>(&self, priority: Priority, func: F)
where
F: FnOnce() + 'static,
{
unsafe extern "C" fn trampoline<F: FnOnce() + 'static>(func: gpointer) -> gboolean {
let func: &mut Option<F> = &mut *(func as *mut Option<F>);
let func = func
.take()
.expect("MainContext::invoke() closure called multiple times");
func();
ffi::G_SOURCE_REMOVE
}
unsafe extern "C" fn destroy_closure<F: FnOnce() + 'static>(ptr: gpointer) {
let _ = Box::<Option<F>>::from_raw(ptr as *mut _);
}
let func = Box::into_raw(Box::new(Some(func)));
ffi::g_main_context_invoke_full(
self.to_glib_none().0,
priority.into_glib(),
Some(trampoline::<F>),
func as gpointer,
Some(destroy_closure::<F>),
)
}
// rustdoc-stripper-ignore-next
/// Call closure with the main context configured as the thread default one.
///
/// The thread default main context is changed in a panic-safe manner before calling `func` and
/// released again afterwards regardless of whether closure panicked or not.
///
/// This will fail if the main context is owned already by another thread.
#[doc(alias = "g_main_context_push_thread_default")]
pub fn with_thread_default<R, F: FnOnce() -> R + Sized>(
&self,
func: F,
) -> Result<R, crate::BoolError> {
let _acquire = self.acquire()?;
let _thread_default = ThreadDefaultContext::new(self);
Ok(func())
}
// rustdoc-stripper-ignore-next
/// Acquire ownership of the main context.
///
/// Ownership will automatically be released again once the returned acquire guard is dropped.
///
/// This will fail if the main context is owned already by another thread.
// rustdoc-stripper-ignore-next-stop
/// Tries to become the owner of the specified context.
/// If some other thread is the owner of the context,
/// returns [`false`] immediately. Ownership is properly
/// recursive: the owner can require ownership again
/// and will release ownership when [`release()`][Self::release()]
/// is called as many times as [`acquire()`][Self::acquire()].
///
/// You must be the owner of a context before you
/// can call [`prepare()`][Self::prepare()], `GLib::MainContext::query()`,
/// `GLib::MainContext::check()`, [`dispatch()`][Self::dispatch()],
/// [`release()`][Self::release()].
///
/// Since 2.76 @self can be [`None`] to use the global-default
/// main context.
///
/// # Returns
///
/// [`true`] if the operation succeeded, and
/// this thread is now the owner of @self.
#[doc(alias = "g_main_context_acquire")]
pub fn acquire(&self) -> Result<MainContextAcquireGuard, crate::BoolError> {
unsafe {
let ret: bool = from_glib(ffi::g_main_context_acquire(self.to_glib_none().0));
if ret {
Ok(MainContextAcquireGuard(self))
} else {
Err(bool_error!("Failed to acquire ownership of main context, already acquired by another thread"))
}
}
}
}
#[must_use = "if unused the main context will be released immediately"]
pub struct MainContextAcquireGuard<'a>(&'a MainContext);
impl<'a> Drop for MainContextAcquireGuard<'a> {
#[doc(alias = "g_main_context_release")]
#[inline]
fn drop(&mut self) {
unsafe {
ffi::g_main_context_release(self.0.to_glib_none().0);
}
}
}
struct ThreadDefaultContext<'a>(&'a MainContext);
impl<'a> ThreadDefaultContext<'a> {
fn new(ctx: &MainContext) -> ThreadDefaultContext {
unsafe {
ffi::g_main_context_push_thread_default(ctx.to_glib_none().0);
}
ThreadDefaultContext(ctx)
}
}
impl<'a> Drop for ThreadDefaultContext<'a> {
#[inline]
fn drop(&mut self) {
unsafe {
ffi::g_main_context_pop_thread_default(self.0.to_glib_none().0);
}
}
}
#[cfg(test)]
mod tests {
use std::{panic, ptr, thread};
use super::*;
#[test]
fn test_invoke() {
let c = MainContext::new();
let l = crate::MainLoop::new(Some(&c), false);
let l_clone = l.clone();
let join_handle = thread::spawn(move || {
c.invoke(move || l_clone.quit());
});
l.run();
join_handle.join().unwrap();
}
fn is_same_context(a: &MainContext, b: &MainContext) -> bool {
ptr::eq(a.to_glib_none().0, b.to_glib_none().0)
}
#[test]
fn test_with_thread_default() {
let a = MainContext::new();
let b = MainContext::new();
assert!(!is_same_context(&a, &b));
a.with_thread_default(|| {
let t = MainContext::thread_default().unwrap();
assert!(is_same_context(&a, &t));
b.with_thread_default(|| {
let t = MainContext::thread_default().unwrap();
assert!(is_same_context(&b, &t));
})
.unwrap();
let t = MainContext::thread_default().unwrap();
assert!(is_same_context(&a, &t));
})
.unwrap();
}
#[test]
fn test_with_thread_default_is_panic_safe() {
let a = MainContext::new();
let b = MainContext::new();
assert!(!is_same_context(&a, &b));
a.with_thread_default(|| {
let t = MainContext::thread_default().unwrap();
assert!(is_same_context(&a, &t));
let result = panic::catch_unwind(|| {
b.with_thread_default(|| {
panic!();
})
.unwrap();
});
assert!(result.is_err());
let t = MainContext::thread_default().unwrap();
assert!(is_same_context(&a, &t));
})
.unwrap();
}
}