1 files changed, 174 insertions, 0 deletions
diff --git a/servo/components/style/gecko/snapshot.rs b/servo/components/style/gecko/snapshot.rs
new file mode 100644
index 0000000000..2ff04406ac
--- /dev/null
+++ b/servo/components/style/gecko/snapshot.rs
@@ -0,0 +1,174 @@
+/* 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 gecko snapshot, that stores the element attributes and state before they
+//! change in order to properly calculate restyle hints.
+
+use crate::dom::TElement;
+use crate::gecko::snapshot_helpers;
+use crate::gecko::wrapper::GeckoElement;
+use crate::gecko_bindings::bindings;
+use crate::gecko_bindings::structs::ServoElementSnapshot;
+use crate::gecko_bindings::structs::ServoElementSnapshotFlags as Flags;
+use crate::gecko_bindings::structs::ServoElementSnapshotTable;
+use crate::invalidation::element::element_wrapper::ElementSnapshot;
+use crate::selector_parser::AttrValue;
+use crate::string_cache::{Atom, Namespace};
+use crate::values::{AtomIdent, AtomString};
+use crate::LocalName;
+use crate::WeakAtom;
+use dom::ElementState;
+use selectors::attr::{AttrSelectorOperation, CaseSensitivity, NamespaceConstraint};
+
+/// A snapshot of a Gecko element.
+pub type GeckoElementSnapshot = ServoElementSnapshot;
+
+/// A map from elements to snapshots for Gecko's style back-end.
+pub type SnapshotMap = ServoElementSnapshotTable;
+
+impl SnapshotMap {
+    /// Gets the snapshot for this element, if any.
+    ///
+    /// FIXME(emilio): The transmute() business we do here is kind of nasty, but
+    /// it's a consequence of the map being a OpaqueNode -> Snapshot table in
+    /// Servo and an Element -> Snapshot table in Gecko.
+    ///
+    /// We should be able to make this a more type-safe with type annotations by
+    /// making SnapshotMap a trait and moving the implementations outside, but
+    /// that's a pain because it implies parameterizing SharedStyleContext.
+    pub fn get<E: TElement>(&self, element: &E) -> Option<&GeckoElementSnapshot> {
+        debug_assert!(element.has_snapshot());
+
+        unsafe {
+            let element = ::std::mem::transmute::<&E, &GeckoElement>(element);
+            bindings::Gecko_GetElementSnapshot(self, element.0).as_ref()
+        }
+    }
+}
+
+impl GeckoElementSnapshot {
+    #[inline]
+    fn has_any(&self, flags: Flags) -> bool {
+        (self.mContains as u8 & flags as u8) != 0
+    }
+
+    /// Returns true if the snapshot has stored state for pseudo-classes
+    /// that depend on things other than `ElementState`.
+    #[inline]
+    pub fn has_other_pseudo_class_state(&self) -> bool {
+        self.has_any(Flags::OtherPseudoClassState)
+    }
+
+    /// Returns true if the snapshot recorded an id change.
+    #[inline]
+    pub fn id_changed(&self) -> bool {
+        self.mIdAttributeChanged()
+    }
+
+    /// Returns true if the snapshot recorded a class attribute change.
+    #[inline]
+    pub fn class_changed(&self) -> bool {
+        self.mClassAttributeChanged()
+    }
+
+    /// Executes the callback once for each attribute that changed.
+    #[inline]
+    pub fn each_attr_changed<F>(&self, mut callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        for attr in self.mChangedAttrNames.iter() {
+            unsafe { AtomIdent::with(attr.mRawPtr, &mut callback) }
+        }
+    }
+
+    /// selectors::Element::attr_matches
+    pub fn attr_matches(
+        &self,
+        ns: &NamespaceConstraint<&Namespace>,
+        local_name: &LocalName,
+        operation: &AttrSelectorOperation<&AttrValue>,
+    ) -> bool {
+        snapshot_helpers::attr_matches(&self.mAttrs, ns, local_name, operation)
+    }
+}
+
+impl ElementSnapshot for GeckoElementSnapshot {
+    fn debug_list_attributes(&self) -> String {
+        use nsstring::nsCString;
+        let mut string = nsCString::new();
+        unsafe {
+            bindings::Gecko_Snapshot_DebugListAttributes(self, &mut string);
+        }
+        String::from_utf8_lossy(&*string).into_owned()
+    }
+
+    fn state(&self) -> Option<ElementState> {
+        if self.has_any(Flags::State) {
+            Some(ElementState::from_bits_retain(self.mState))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn has_attrs(&self) -> bool {
+        self.has_any(Flags::Attributes)
+    }
+
+    #[inline]
+    fn id_attr(&self) -> Option<&WeakAtom> {
+        if !self.has_any(Flags::Id) {
+            return None;
+        }
+
+        snapshot_helpers::get_id(&*self.mAttrs)
+    }
+
+    #[inline]
+    fn is_part(&self, name: &AtomIdent) -> bool {
+        let attr = match snapshot_helpers::find_attr(&*self.mAttrs, &atom!("part")) {
+            Some(attr) => attr,
+            None => return false,
+        };
+
+        snapshot_helpers::has_class_or_part(name, CaseSensitivity::CaseSensitive, attr)
+    }
+
+    #[inline]
+    fn imported_part(&self, name: &AtomIdent) -> Option<AtomIdent> {
+        snapshot_helpers::imported_part(&*self.mAttrs, name)
+    }
+
+    #[inline]
+    fn has_class(&self, name: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool {
+        if !self.has_any(Flags::MaybeClass) {
+            return false;
+        }
+
+        snapshot_helpers::has_class_or_part(name, case_sensitivity, &self.mClass)
+    }
+
+    #[inline]
+    fn each_class<F>(&self, callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        if !self.has_any(Flags::MaybeClass) {
+            return;
+        }
+
+        snapshot_helpers::each_class_or_part(&self.mClass, callback)
+    }
+
+    #[inline]
+    fn lang_attr(&self) -> Option<AtomString> {
+        let ptr = unsafe { bindings::Gecko_SnapshotLangValue(self) };
+        if ptr.is_null() {
+            None
+        } else {
+            Some(AtomString(unsafe { Atom::from_addrefed(ptr) }))
+        }
+    }
+}