1 files changed, 104 insertions, 0 deletions
diff --git a/servo/components/style/stylesheets/style_rule.rs b/servo/components/style/stylesheets/style_rule.rs
new file mode 100644
index 0000000000..d5a22d6fc2
--- /dev/null
+++ b/servo/components/style/stylesheets/style_rule.rs
@@ -0,0 +1,104 @@
+/* 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/. */
+
+//! A style rule.
+
+use crate::properties::PropertyDeclarationBlock;
+use crate::selector_parser::SelectorImpl;
+use crate::shared_lock::{
+    DeepCloneParams, DeepCloneWithLock, Locked, SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard,
+};
+use crate::str::CssStringWriter;
+use crate::stylesheets::CssRules;
+use cssparser::SourceLocation;
+#[cfg(feature = "gecko")]
+use malloc_size_of::MallocUnconditionalShallowSizeOf;
+#[cfg(feature = "gecko")]
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use selectors::SelectorList;
+use servo_arc::Arc;
+use std::fmt::{self, Write};
+
+/// A style rule, with selectors and declarations.
+#[derive(Debug, ToShmem)]
+pub struct StyleRule {
+    /// The list of selectors in this rule.
+    pub selectors: SelectorList<SelectorImpl>,
+    /// The declaration block with the properties it contains.
+    pub block: Arc<Locked<PropertyDeclarationBlock>>,
+    /// The nested rules to this style rule. Only non-`None` when nesting is enabled.
+    pub rules: Option<Arc<Locked<CssRules>>>,
+    /// The location in the sheet where it was found.
+    pub source_location: SourceLocation,
+}
+
+impl DeepCloneWithLock for StyleRule {
+    /// Deep clones this StyleRule.
+    fn deep_clone_with_lock(
+        &self,
+        lock: &SharedRwLock,
+        guard: &SharedRwLockReadGuard,
+        params: &DeepCloneParams,
+    ) -> StyleRule {
+        StyleRule {
+            selectors: self.selectors.clone(),
+            block: Arc::new(lock.wrap(self.block.read_with(guard).clone())),
+            rules: self.rules.as_ref().map(|rules| {
+                let rules = rules.read_with(guard);
+                Arc::new(lock.wrap(rules.deep_clone_with_lock(lock, guard, params)))
+            }),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
+impl StyleRule {
+    /// Measure heap usage.
+    #[cfg(feature = "gecko")]
+    pub fn size_of(&self, guard: &SharedRwLockReadGuard, ops: &mut MallocSizeOfOps) -> usize {
+        let mut n = 0;
+        n += self.selectors.0.size_of(ops);
+        n += self.block.unconditional_shallow_size_of(ops) +
+            self.block.read_with(guard).size_of(ops);
+        if let Some(ref rules) = self.rules {
+            n += rules.unconditional_shallow_size_of(ops) +
+                rules.read_with(guard).size_of(guard, ops)
+        }
+        n
+    }
+}
+
+impl ToCssWithGuard for StyleRule {
+    /// https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSStyleRule
+    fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
+        use cssparser::ToCss;
+        // Step 1
+        self.selectors.to_css(dest)?;
+        dest.write_str(" {")?;
+
+        // Step 2
+        let declaration_block = self.block.read_with(guard);
+        let has_declarations = !declaration_block.declarations().is_empty();
+
+        // Step 3
+        if let Some(ref rules) = self.rules {
+            let rules = rules.read_with(guard);
+            // Step 6 (here because it's more convenient)
+            if !rules.is_empty() {
+                if has_declarations {
+                    dest.write_str("\n  ")?;
+                    declaration_block.to_css(dest)?;
+                }
+                return rules.to_css_block_without_opening(guard, dest);
+            }
+        }
+
+        // Steps 4 & 5
+        if has_declarations {
+            dest.write_char(' ')?;
+            declaration_block.to_css(dest)?;
+        }
+        dest.write_str(" }")
+    }
+}