1 files changed, 301 insertions, 0 deletions
diff --git a/servo/components/style/stylesheets/import_rule.rs b/servo/components/style/stylesheets/import_rule.rs
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+++ b/servo/components/style/stylesheets/import_rule.rs
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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/. */
+
+//! The [`@import`][import] at-rule.
+//!
+//! [import]: https://drafts.csswg.org/css-cascade-3/#at-import
+
+use crate::media_queries::MediaList;
+use crate::parser::{Parse, ParserContext};
+use crate::shared_lock::{
+    DeepCloneParams, DeepCloneWithLock, SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard,
+};
+use crate::str::CssStringWriter;
+use crate::stylesheets::{
+    layer_rule::LayerName, supports_rule::SupportsCondition, CssRule, CssRuleType,
+    StylesheetInDocument,
+};
+use crate::values::CssUrl;
+use cssparser::{Parser, SourceLocation};
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+use to_shmem::{self, SharedMemoryBuilder, ToShmem};
+
+/// A sheet that is held from an import rule.
+#[cfg(feature = "gecko")]
+#[derive(Debug)]
+pub enum ImportSheet {
+    /// A bonafide stylesheet.
+    Sheet(crate::gecko::data::GeckoStyleSheet),
+
+    /// An @import created while parsing off-main-thread, whose Gecko sheet has
+    /// yet to be created and attached.
+    Pending,
+
+    /// An @import created with a false <supports-condition>, so will never be fetched.
+    Refused,
+}
+
+#[cfg(feature = "gecko")]
+impl ImportSheet {
+    /// Creates a new ImportSheet from a GeckoStyleSheet.
+    pub fn new(sheet: crate::gecko::data::GeckoStyleSheet) -> Self {
+        ImportSheet::Sheet(sheet)
+    }
+
+    /// Creates a pending ImportSheet for a load that has not started yet.
+    pub fn new_pending() -> Self {
+        ImportSheet::Pending
+    }
+
+    /// Creates a refused ImportSheet for a load that will not happen.
+    pub fn new_refused() -> Self {
+        ImportSheet::Refused
+    }
+
+    /// Returns a reference to the GeckoStyleSheet in this ImportSheet, if it
+    /// exists.
+    pub fn as_sheet(&self) -> Option<&crate::gecko::data::GeckoStyleSheet> {
+        match *self {
+            ImportSheet::Sheet(ref s) => {
+                debug_assert!(!s.hack_is_null());
+                if s.hack_is_null() {
+                    return None;
+                }
+                Some(s)
+            },
+            ImportSheet::Refused | ImportSheet::Pending => None,
+        }
+    }
+
+    /// Returns the media list for this import rule.
+    pub fn media<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> Option<&'a MediaList> {
+        self.as_sheet().and_then(|s| s.media(guard))
+    }
+
+    /// Returns the rule list for this import rule.
+    pub fn rules<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> &'a [CssRule] {
+        match self.as_sheet() {
+            Some(s) => s.rules(guard),
+            None => &[],
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl DeepCloneWithLock for ImportSheet {
+    fn deep_clone_with_lock(
+        &self,
+        _lock: &SharedRwLock,
+        _guard: &SharedRwLockReadGuard,
+        params: &DeepCloneParams,
+    ) -> Self {
+        use crate::gecko::data::GeckoStyleSheet;
+        use crate::gecko_bindings::bindings;
+        match *self {
+            ImportSheet::Sheet(ref s) => {
+                let clone = unsafe {
+                    bindings::Gecko_StyleSheet_Clone(s.raw() as *const _, params.reference_sheet)
+                };
+                ImportSheet::Sheet(unsafe { GeckoStyleSheet::from_addrefed(clone) })
+            },
+            ImportSheet::Pending => ImportSheet::Pending,
+            ImportSheet::Refused => ImportSheet::Refused,
+        }
+    }
+}
+
+/// A sheet that is held from an import rule.
+#[cfg(feature = "servo")]
+#[derive(Debug)]
+pub struct ImportSheet(pub ::servo_arc::Arc<crate::stylesheets::Stylesheet>);
+
+#[cfg(feature = "servo")]
+impl ImportSheet {
+    /// Returns the media list for this import rule.
+    pub fn media<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> Option<&'a MediaList> {
+        self.0.media(guard)
+    }
+
+    /// Returns the rules for this import rule.
+    pub fn rules<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> &'a [CssRule] {
+        self.0.rules()
+    }
+}
+
+#[cfg(feature = "servo")]
+impl DeepCloneWithLock for ImportSheet {
+    fn deep_clone_with_lock(
+        &self,
+        _lock: &SharedRwLock,
+        _guard: &SharedRwLockReadGuard,
+        _params: &DeepCloneParams,
+    ) -> Self {
+        use servo_arc::Arc;
+
+        ImportSheet(Arc::new((&*self.0).clone()))
+    }
+}
+
+/// The layer specified in an import rule (can be none, anonymous, or named).
+#[derive(Debug, Clone)]
+pub enum ImportLayer {
+    /// No layer specified
+    None,
+
+    /// Anonymous layer (`layer`)
+    Anonymous,
+
+    /// Named layer (`layer(name)`)
+    Named(LayerName),
+}
+
+/// The supports condition in an import rule.
+#[derive(Debug, Clone)]
+pub struct ImportSupportsCondition {
+    /// The supports condition.
+    pub condition: SupportsCondition,
+
+    /// If the import is enabled, from the result of the import condition.
+    pub enabled: bool,
+}
+
+impl ToCss for ImportLayer {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            ImportLayer::None => Ok(()),
+            ImportLayer::Anonymous => dest.write_str("layer"),
+            ImportLayer::Named(ref name) => {
+                dest.write_str("layer(")?;
+                name.to_css(dest)?;
+                dest.write_char(')')
+            },
+        }
+    }
+}
+
+/// The [`@import`][import] at-rule.
+///
+/// [import]: https://drafts.csswg.org/css-cascade-3/#at-import
+#[derive(Debug)]
+pub struct ImportRule {
+    /// The `<url>` this `@import` rule is loading.
+    pub url: CssUrl,
+
+    /// The stylesheet is always present. However, in the case of gecko async
+    /// parsing, we don't actually have a Gecko sheet at first, and so the
+    /// ImportSheet just has stub behavior until it appears.
+    pub stylesheet: ImportSheet,
+
+    /// A <supports-condition> for the rule.
+    pub supports: Option<ImportSupportsCondition>,
+
+    /// A `layer()` function name.
+    pub layer: ImportLayer,
+
+    /// The line and column of the rule's source code.
+    pub source_location: SourceLocation,
+}
+
+impl ImportRule {
+    /// Parses the layer() / layer / supports() part of the import header, as per
+    /// https://drafts.csswg.org/css-cascade-5/#at-import:
+    ///
+    ///     [ layer | layer(<layer-name>) ]?
+    ///     [ supports([ <supports-condition> | <declaration> ]) ]?
+    ///
+    /// We do this here so that the import preloader can look at this without having to parse the
+    /// whole import rule or parse the media query list or what not.
+    pub fn parse_layer_and_supports<'i, 't>(
+        input: &mut Parser<'i, 't>,
+        context: &mut ParserContext,
+    ) -> (ImportLayer, Option<ImportSupportsCondition>) {
+        let layer = if input
+            .try_parse(|input| input.expect_ident_matching("layer"))
+            .is_ok()
+        {
+            ImportLayer::Anonymous
+        } else {
+            input
+                .try_parse(|input| {
+                    input.expect_function_matching("layer")?;
+                    input
+                        .parse_nested_block(|input| LayerName::parse(context, input))
+                        .map(|name| ImportLayer::Named(name))
+                })
+                .ok()
+                .unwrap_or(ImportLayer::None)
+        };
+
+        let supports = if !static_prefs::pref!("layout.css.import-supports.enabled") {
+            None
+        } else {
+            input
+                .try_parse(SupportsCondition::parse_for_import)
+                .map(|condition| {
+                    let enabled = context
+                        .nest_for_rule(CssRuleType::Style, |context| condition.eval(context));
+                    ImportSupportsCondition { condition, enabled }
+                })
+                .ok()
+        };
+
+        (layer, supports)
+    }
+}
+
+impl ToShmem for ImportRule {
+    fn to_shmem(&self, _builder: &mut SharedMemoryBuilder) -> to_shmem::Result<Self> {
+        Err(String::from(
+            "ToShmem failed for ImportRule: cannot handle imported style sheets",
+        ))
+    }
+}
+
+impl DeepCloneWithLock for ImportRule {
+    fn deep_clone_with_lock(
+        &self,
+        lock: &SharedRwLock,
+        guard: &SharedRwLockReadGuard,
+        params: &DeepCloneParams,
+    ) -> Self {
+        ImportRule {
+            url: self.url.clone(),
+            stylesheet: self.stylesheet.deep_clone_with_lock(lock, guard, params),
+            supports: self.supports.clone(),
+            layer: self.layer.clone(),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
+impl ToCssWithGuard for ImportRule {
+    fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
+        dest.write_str("@import ")?;
+        self.url.to_css(&mut CssWriter::new(dest))?;
+
+        if !matches!(self.layer, ImportLayer::None) {
+            dest.write_char(' ')?;
+            self.layer.to_css(&mut CssWriter::new(dest))?;
+        }
+
+        if let Some(ref supports) = self.supports {
+            dest.write_str(" supports(")?;
+            supports.condition.to_css(&mut CssWriter::new(dest))?;
+            dest.write_char(')')?;
+        }
+
+        if let Some(media) = self.stylesheet.media(guard) {
+            if !media.is_empty() {
+                dest.write_char(' ')?;
+                media.to_css(&mut CssWriter::new(dest))?;
+            }
+        }
+
+        dest.write_char(';')
+    }
+}