gecko-dev/servo/ports/geckolib/glue.rs

/* 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 http://mozilla.org/MPL/2.0/. */

#![allow(unsafe_code)]

use app_units::Au;
use data::PerDocumentStyleData;
use env_logger;
use euclid::Size2D;
use gecko_bindings::bindings::{RawGeckoDocument, RawGeckoElement, RawGeckoNode};
use gecko_bindings::bindings::{RawServoStyleSet, RawServoStyleSheet, ServoComputedValues, ServoNodeData};
use gecko_bindings::bindings::{ThreadSafePrincipalHolder, ThreadSafeURIHolder, nsIAtom};
use gecko_bindings::ptr::{GeckoArcPrincipal, GeckoArcURI};
use gecko_bindings::structs::SheetParsingMode;
use properties::GeckoComputedValues;
use selector_impl::{GeckoSelectorImpl, PseudoElement, SharedStyleContext, Stylesheet};
use std::marker::PhantomData;
use std::mem::{forget, transmute};
use std::ptr;
use std::slice;
use std::str::from_utf8_unchecked;
use std::sync::{Arc, Mutex};
use style::context::{ReflowGoal};
use style::dom::{TDocument, TElement, TNode};
use style::error_reporting::StdoutErrorReporter;
use style::parallel;
use style::parser::ParserContextExtraData;
use style::properties::ComputedValues;
use style::selector_impl::{SelectorImplExt, PseudoElementCascadeType};
use style::stylesheets::Origin;
use traversal::RecalcStyleOnly;
use url::Url;
use util::arc_ptr_eq;
use wrapper::{GeckoDocument, GeckoElement, GeckoNode, NonOpaqueStyleData};

// TODO: This is ugly and should go away once we get an atom back-end.
pub fn pseudo_element_from_atom(pseudo: *mut nsIAtom,
                                in_ua_stylesheet: bool) -> Result<PseudoElement, String> {
    use gecko_bindings::bindings::Gecko_GetAtomAsUTF16;
    use selectors::parser::{ParserContext, SelectorImpl};

    let pseudo_string = unsafe {
        let mut length = 0;
        let mut buff = Gecko_GetAtomAsUTF16(pseudo, &mut length);

        // Handle the annoying preceding colon in front of everything in nsCSSAnonBoxList.h.
        debug_assert!(length >= 2 && *buff == ':' as u16 && *buff.offset(1) != ':' as u16);
        buff = buff.offset(1);
        length -= 1;

        String::from_utf16(slice::from_raw_parts(buff, length as usize)).unwrap()
    };

    let mut context = ParserContext::new();
    context.in_user_agent_stylesheet = in_ua_stylesheet;
    GeckoSelectorImpl::parse_pseudo_element(&context, &pseudo_string).map_err(|_| pseudo_string)
}

/*
 * For Gecko->Servo function calls, we need to redeclare the same signature that was declared in
 * the C header in Gecko. In order to catch accidental mismatches, we run rust-bindgen against
 * those signatures as well, giving us a second declaration of all the Servo_* functions in this
 * crate. If there's a mismatch, LLVM will assert and abort, which is a rather awful thing to
 * depend on but good enough for our purposes.
 */

#[no_mangle]
pub extern "C" fn Servo_Initialize() -> () {
    // Enable standard Rust logging.
    //
    // See https://doc.rust-lang.org/log/env_logger/index.html for instructions.
    env_logger::init().unwrap();
}

#[no_mangle]
pub extern "C" fn Servo_RestyleDocument(doc: *mut RawGeckoDocument, raw_data: *mut RawServoStyleSet) -> () {
    let document = unsafe { GeckoDocument::from_raw(doc) };
    let node = match document.root_node() {
        Some(x) => x,
        None => return,
    };
    let data = unsafe { &mut *(raw_data as *mut PerDocumentStyleData) };

    // Force the creation of our lazily-constructed initial computed values on
    // the main thread, since it's not safe to call elsewhere.
    //
    // FIXME(bholley): this should move into Servo_Initialize as soon as we get
    // rid of the HackilyFindSomeDeviceContext stuff that happens during
    // initial_values computation, since that stuff needs to be called further
    // along in startup than the sensible place to call Servo_Initialize.
    GeckoComputedValues::initial_values();

    let _needs_dirtying = Arc::get_mut(&mut data.stylist).unwrap()
                              .update(&data.stylesheets, data.stylesheets_changed);
    data.stylesheets_changed = false;

    let shared_style_context = SharedStyleContext {
        viewport_size: Size2D::new(Au(0), Au(0)),
        screen_size_changed: false,
        generation: 0,
        goal: ReflowGoal::ForScriptQuery,
        stylist: data.stylist.clone(),
        new_animations_sender: Mutex::new(data.new_animations_sender.clone()),
        running_animations: data.running_animations.clone(),
        expired_animations: data.expired_animations.clone(),
        error_reporter: Box::new(StdoutErrorReporter),
    };

    if node.is_dirty() || node.has_dirty_descendants() {
        parallel::traverse_dom::<GeckoNode, RecalcStyleOnly>(node, &shared_style_context, &mut data.work_queue);
    }
}

#[no_mangle]
pub extern "C" fn Servo_DropNodeData(data: *mut ServoNodeData) -> () {
    unsafe {
        let _ = Box::<NonOpaqueStyleData>::from_raw(data as *mut NonOpaqueStyleData);
    }
}

#[no_mangle]
pub extern "C" fn Servo_StylesheetFromUTF8Bytes(bytes: *const u8,
                                                length: u32,
                                                mode: SheetParsingMode,
                                                base: *mut ThreadSafeURIHolder,
                                                referrer: *mut ThreadSafeURIHolder,
                                                principal: *mut ThreadSafePrincipalHolder)
                                                -> *mut RawServoStyleSheet {

    let input = unsafe { from_utf8_unchecked(slice::from_raw_parts(bytes, length as usize)) };

    let origin = match mode {
        SheetParsingMode::eAuthorSheetFeatures => Origin::Author,
        SheetParsingMode::eUserSheetFeatures => Origin::User,
        SheetParsingMode::eAgentSheetFeatures => Origin::UserAgent,
    };

    // FIXME(heycam): Pass in the real base URL.
    let url = Url::parse("about:none").unwrap();
    let extra_data = ParserContextExtraData {
        base: Some(GeckoArcURI::new(base)),
        referrer: Some(GeckoArcURI::new(referrer)),
        principal: Some(GeckoArcPrincipal::new(principal)),
    };
    let sheet = Arc::new(Stylesheet::from_str(input, url, origin, Box::new(StdoutErrorReporter),
                                              extra_data));
    unsafe {
        transmute(sheet)
    }
}

pub struct ArcHelpers<GeckoType, ServoType> {
    phantom1: PhantomData<GeckoType>,
    phantom2: PhantomData<ServoType>,
}


impl<GeckoType, ServoType> ArcHelpers<GeckoType, ServoType> {
    pub fn with<F, Output>(raw: *mut GeckoType, cb: F) -> Output
                           where F: FnOnce(&Arc<ServoType>) -> Output {
        debug_assert!(!raw.is_null());

        let owned = unsafe { Self::into(raw) };
        let result = cb(&owned);
        forget(owned);
        result
    }

    pub fn maybe_with<F, Output>(maybe_raw: *mut GeckoType, cb: F) -> Output
                                 where F: FnOnce(Option<&Arc<ServoType>>) -> Output {
        let owned = if maybe_raw.is_null() {
            None
        } else {
            Some(unsafe { Self::into(maybe_raw) })
        };

        let result = cb(owned.as_ref());
        forget(owned);

        result
    }

    pub unsafe fn into(ptr: *mut GeckoType) -> Arc<ServoType> {
        transmute(ptr)
    }

    pub fn from(owned: Arc<ServoType>) -> *mut GeckoType {
        unsafe { transmute(owned) }
    }

    pub unsafe fn addref(ptr: *mut GeckoType) {
        Self::with(ptr, |arc| forget(arc.clone()));
    }

    pub unsafe fn release(ptr: *mut GeckoType) {
        let _ = Self::into(ptr);
    }
}

#[no_mangle]
pub extern "C" fn Servo_AppendStyleSheet(raw_sheet: *mut RawServoStyleSheet,
                                         raw_data: *mut RawServoStyleSet) {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);
    Helpers::with(raw_sheet, |sheet| {
        data.stylesheets.retain(|x| !arc_ptr_eq(x, sheet));
        data.stylesheets.push(sheet.clone());
        data.stylesheets_changed = true;
    });
}

#[no_mangle]
pub extern "C" fn Servo_PrependStyleSheet(raw_sheet: *mut RawServoStyleSheet,
                                          raw_data: *mut RawServoStyleSet) {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);
    Helpers::with(raw_sheet, |sheet| {
        data.stylesheets.retain(|x| !arc_ptr_eq(x, sheet));
        data.stylesheets.insert(0, sheet.clone());
        data.stylesheets_changed = true;
    })
}

#[no_mangle]
pub extern "C" fn Servo_InsertStyleSheetBefore(raw_sheet: *mut RawServoStyleSheet,
                                               raw_reference: *mut RawServoStyleSheet,
                                               raw_data: *mut RawServoStyleSet) {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);
    Helpers::with(raw_sheet, |sheet| {
        Helpers::with(raw_reference, |reference| {
            data.stylesheets.retain(|x| !arc_ptr_eq(x, sheet));
            let index = data.stylesheets.iter().position(|x| arc_ptr_eq(x, reference)).unwrap();
            data.stylesheets.insert(index, sheet.clone());
            data.stylesheets_changed = true;
        })
    })
}

#[no_mangle]
pub extern "C" fn Servo_RemoveStyleSheet(raw_sheet: *mut RawServoStyleSheet,
                                         raw_data: *mut RawServoStyleSet) {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);
    Helpers::with(raw_sheet, |sheet| {
        data.stylesheets.retain(|x| !arc_ptr_eq(x, sheet));
        data.stylesheets_changed = true;
    });
}

#[no_mangle]
pub extern "C" fn Servo_StyleSheetHasRules(raw_sheet: *mut RawServoStyleSheet) -> bool {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    Helpers::with(raw_sheet, |sheet| !sheet.rules.is_empty())
}

#[no_mangle]
pub extern "C" fn Servo_AddRefStyleSheet(sheet: *mut RawServoStyleSheet) -> () {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    unsafe { Helpers::addref(sheet) };
}

#[no_mangle]
pub extern "C" fn Servo_ReleaseStyleSheet(sheet: *mut RawServoStyleSheet) -> () {
    type Helpers = ArcHelpers<RawServoStyleSheet, Stylesheet>;
    unsafe { Helpers::release(sheet) };
}

#[no_mangle]
pub extern "C" fn Servo_GetComputedValues(node: *mut RawGeckoNode)
     -> *mut ServoComputedValues {
    let node = unsafe { GeckoNode::from_raw(node) };
    let arc_cv = match node.borrow_data().map_or(None, |data| data.style.clone()) {
        Some(style) => style,
        None => {
            // FIXME(bholley): This case subverts the intended semantics of this
            // function, and exists only to make stylo builds more robust corner-
            // cases where Gecko wants the style for a node that Servo never
            // traversed. We should remove this as soon as possible.
            error!("stylo: encountered unstyled node, substituting default values.");
            Arc::new(GeckoComputedValues::initial_values().clone())
        },
    };
    unsafe { transmute(arc_cv) }
}

#[no_mangle]
pub extern "C" fn Servo_GetComputedValuesForAnonymousBox(parent_style_or_null: *mut ServoComputedValues,
                                                         pseudo_tag: *mut nsIAtom,
                                                         raw_data: *mut RawServoStyleSet)
     -> *mut ServoComputedValues {
    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);

    let pseudo = match pseudo_element_from_atom(pseudo_tag, /* ua_stylesheet = */ true) {
        Ok(pseudo) => pseudo,
        Err(pseudo) => {
            warn!("stylo: Unable to parse anonymous-box pseudo-element: {}", pseudo);
            return ptr::null_mut();
        }
    };

    type Helpers = ArcHelpers<ServoComputedValues, GeckoComputedValues>;

    Helpers::maybe_with(parent_style_or_null, |maybe_parent| {
        let new_computed = data.stylist.precomputed_values_for_pseudo(&pseudo, maybe_parent);
        new_computed.map_or(ptr::null_mut(), |c| Helpers::from(c))
    })
}

#[no_mangle]
pub extern "C" fn Servo_GetComputedValuesForPseudoElement(parent_style: *mut ServoComputedValues,
                                                          match_element: *mut RawGeckoElement,
                                                          pseudo_tag: *mut nsIAtom,
                                                          raw_data: *mut RawServoStyleSet,
                                                          is_probe: bool)
     -> *mut ServoComputedValues {
    debug_assert!(!match_element.is_null());

    let parent_or_null = || {
        if is_probe {
            ptr::null_mut()
        } else {
            Servo_AddRefComputedValues(parent_style);
            parent_style
        }
    };

    let pseudo = match pseudo_element_from_atom(pseudo_tag, /* ua_stylesheet = */ true) {
        Ok(pseudo) => pseudo,
        Err(pseudo) => {
            warn!("stylo: Unable to parse anonymous-box pseudo-element: {}", pseudo);
            return parent_or_null();
        }
    };


    let data = PerDocumentStyleData::borrow_mut_from_raw(raw_data);

    let element = unsafe { GeckoElement::from_raw(match_element) };

    type Helpers = ArcHelpers<ServoComputedValues, GeckoComputedValues>;

    match GeckoSelectorImpl::pseudo_element_cascade_type(&pseudo) {
        PseudoElementCascadeType::Eager => {
            let node = element.as_node();
            let maybe_computed = node.borrow_data()
                                     .and_then(|data| {
                                         data.per_pseudo.get(&pseudo).map(|c| c.clone())
                                     });
            maybe_computed.map_or_else(parent_or_null, Helpers::from)
        }
        PseudoElementCascadeType::Lazy => {
            Helpers::with(parent_style, |parent| {
                data.stylist
                    .lazily_compute_pseudo_element_style(&element, &pseudo, parent)
                    .map_or_else(parent_or_null, Helpers::from)
            })
        }
        PseudoElementCascadeType::Precomputed => {
            unreachable!("Anonymous pseudo found in \
                         Servo_GetComputedValuesForPseudoElement");
        }
    }
}

#[no_mangle]
pub extern "C" fn Servo_InheritComputedValues(parent_style: *mut ServoComputedValues)
     -> *mut ServoComputedValues {
    type Helpers = ArcHelpers<ServoComputedValues, GeckoComputedValues>;
    Helpers::with(parent_style, |parent| {
        let style = GeckoComputedValues::inherit_from(parent);
        Helpers::from(style)
    })
}

#[no_mangle]
pub extern "C" fn Servo_AddRefComputedValues(ptr: *mut ServoComputedValues) -> () {
    type Helpers = ArcHelpers<ServoComputedValues, GeckoComputedValues>;
    unsafe { Helpers::addref(ptr) };
}

#[no_mangle]
pub extern "C" fn Servo_ReleaseComputedValues(ptr: *mut ServoComputedValues) -> () {
    type Helpers = ArcHelpers<ServoComputedValues, GeckoComputedValues>;
    unsafe { Helpers::release(ptr) };
}

#[no_mangle]
pub extern "C" fn Servo_InitStyleSet() -> *mut RawServoStyleSet {
    let data = Box::new(PerDocumentStyleData::new());
    Box::into_raw(data) as *mut RawServoStyleSet
}

#[no_mangle]
pub extern "C" fn Servo_DropStyleSet(data: *mut RawServoStyleSet) -> () {
    unsafe {
        let _ = Box::<PerDocumentStyleData>::from_raw(data as *mut PerDocumentStyleData);
    }
}