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// Copyright 2013-2015, The Gtk-rs Project Developers.
// See the COPYRIGHT file at the top-level directory of this distribution.
// Licensed under the MIT license, see the LICENSE file or <http://opensource.org/licenses/MIT>

//! General — Library initialization and miscellaneous functions

use std::cell::Cell;
use std::ptr;
use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};

use ffi;

thread_local! {
    static IS_MAIN_THREAD: Cell<bool> = Cell::new(false)
}

static INITIALIZED: AtomicBool = ATOMIC_BOOL_INIT;

/// Asserts that this is the main thread and either `gdk::init` or `gtk::init` has been called.
macro_rules! assert_initialized_main_thread {
    () => (
        if !::rt::is_initialized_main_thread() {
            if ::rt::is_initialized() {
                panic!("GDK may only be used from the main thread.");
            }
            else {
                panic!("GDK has not been initialized. Call `gdk::init` or `gtk::init` first.");
            }
        }
    )
}

/// No-op.
macro_rules! skip_assert_initialized {
    () => ()
}

/// Asserts that neither `gdk::init` nor `gtk::init` has been called.
macro_rules! assert_not_initialized {
    () => (
        if ::rt::is_initialized() {
            panic!("This function has to be called before `gdk::init` or `gtk::init`.");
        }
    )
}

macro_rules! callback_guard {
    () => (
        let _guard = ::glib::CallbackGuard::new();
        if cfg!(debug_assertions) {
            assert_initialized_main_thread!();
        }
    )
}

/// Returns `true` if GDK has been initialized.
#[inline]
pub fn is_initialized() -> bool {
    skip_assert_initialized!();
    INITIALIZED.load(Ordering::Acquire)
}

/// Returns `true` if GDK has been initialized and this is the main thread.
#[inline]
pub fn is_initialized_main_thread() -> bool {
    skip_assert_initialized!();
    IS_MAIN_THREAD.with(|c| c.get())
}

/// Informs this crate that GDK has been initialized and the current thread is the main one.
pub unsafe fn set_initialized() {
    skip_assert_initialized!();
    if is_initialized_main_thread() {
        return;
    }
    else if is_initialized() {
        panic!("Attempted to initialize GDK from two different threads.");
    }
    INITIALIZED.store(true, Ordering::Release);
    IS_MAIN_THREAD.with(|c| c.set(true));
}

pub fn init() {
    assert_not_initialized!();
    unsafe {
        ffi::gdk_init(ptr::null_mut(), ptr::null_mut());
        set_initialized();
    }
}