servo-script-bindings 0.2.0

A component of the servo web-engine.
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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

use std::thread;

use js::jsapi::{HideScriptedCaller, UnhideScriptedCaller};
use js::rust::Runtime;

use crate::DomTypes;
use crate::interfaces::{DomHelpers, GlobalScopeHelpers};
use crate::root::Dom;
use crate::script_runtime::temp_cx;

#[derive(Debug, Eq, JSTraceable, PartialEq)]
pub enum StackEntryKind {
    Incumbent,
    Entry,
}

#[cfg_attr(crown, expect(crown::unrooted_must_root))]
#[derive(JSTraceable)]
pub struct StackEntry<D: DomTypes> {
    pub global: Dom<D::GlobalScope>,
    pub kind: StackEntryKind,
}

/// Wrapper that pushes and pops entries from the script settings stack.
///
/// <https://html.spec.whatwg.org/multipage/#prepare-to-run-script>
/// <https://html.spec.whatwg.org/multipage/#clean-up-after-running-script>
pub fn run_a_script<D: DomTypes, R>(global: &D::GlobalScope, f: impl FnOnce() -> R) -> R {
    let settings_stack = <D as DomHelpers<D>>::settings_stack();
    let _span = settings_stack.with(|stack| {
        trace!("Prepare to run script with {:p}", global);
        let mut stack = stack.borrow_mut();
        stack.push(StackEntry {
            global: Dom::from_ref(global),
            kind: StackEntryKind::Entry,
        });
        profile_traits::info_span!("ScriptEvaluate", url = global.get_url().to_string()).entered()
    });
    let result = f();
    let stack_is_empty = settings_stack.with(|stack| {
        let mut stack = stack.borrow_mut();
        let entry = stack.pop().unwrap();
        assert_eq!(
            &*entry.global as *const D::GlobalScope, global as *const D::GlobalScope,
            "Dropped AutoEntryScript out of order."
        );
        assert_eq!(entry.kind, StackEntryKind::Entry);
        trace!("Clean up after running script with {:p}", &*entry.global);
        stack.is_empty()
    });

    // Step 5
    if !thread::panicking() && stack_is_empty {
        let mut cx = unsafe { temp_cx() };
        global.perform_a_microtask_checkpoint(&mut cx);
    }
    result
}

/// Wrapper that pushes and pops entries from the script settings stack.
///
/// <https://html.spec.whatwg.org/multipage/#prepare-to-run-a-callback>
/// <https://html.spec.whatwg.org/multipage/#clean-up-after-running-a-callback>
pub fn run_a_callback<D: DomTypes, R>(global: &D::GlobalScope, f: impl FnOnce() -> R) -> R {
    let settings_stack = <D as DomHelpers<D>>::settings_stack();
    let cx = Runtime::get().expect("Creating a new incumbent script after runtime shutdown");
    // <https://html.spec.whatwg.org/multipage/#prepare-to-run-a-callback>
    // Step 2-3.
    unsafe {
        HideScriptedCaller(cx.as_ptr());
    }
    settings_stack.with(|stack| {
        trace!("Prepare to run a callback with {:p}", global);
        // Step 1.
        let mut stack = stack.borrow_mut();
        stack.push(StackEntry {
            global: Dom::from_ref(global),
            kind: StackEntryKind::Incumbent,
        });
    });
    let result = f();
    // <https://html.spec.whatwg.org/multipage/#clean-up-after-running-a-callback>
    settings_stack.with(|stack| {
        // Step 4.
        let mut stack = stack.borrow_mut();
        let entry = stack.pop().unwrap();
        // Step 3.
        assert_eq!(
            &*entry.global as *const D::GlobalScope as usize,
            global as *const D::GlobalScope as usize,
            "Dropped AutoIncumbentScript out of order."
        );
        assert_eq!(entry.kind, StackEntryKind::Incumbent);
        trace!(
            "Clean up after running a callback with {:p}",
            &*entry.global
        );
    });
    unsafe {
        // Step 1-2.
        UnhideScriptedCaller(cx.as_ptr());
    }
    result
}