1 files changed, 82 insertions, 0 deletions
diff --git a/servo/components/style/values/specified/gecko.rs b/servo/components/style/values/specified/gecko.rs
new file mode 100644
index 0000000000..e721add59c
--- /dev/null
+++ b/servo/components/style/values/specified/gecko.rs
@@ -0,0 +1,82 @@
+/* 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/. */
+
+//! Specified types for legacy Gecko-only properties.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{self, Length, LengthPercentage};
+use crate::values::generics::rect::Rect;
+use cssparser::{Parser, Token};
+use std::fmt;
+use style_traits::values::SequenceWriter;
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+
+fn parse_pixel_or_percent<'i, 't>(
+    _context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+) -> Result<LengthPercentage, ParseError<'i>> {
+    let location = input.current_source_location();
+    let token = input.next()?;
+    let value = match *token {
+        Token::Dimension {
+            value, ref unit, ..
+        } => {
+            match_ignore_ascii_case! { unit,
+                "px" => Ok(LengthPercentage::new_length(Length::new(value))),
+                _ => Err(()),
+            }
+        },
+        Token::Percentage { unit_value, .. } => Ok(LengthPercentage::new_percent(
+            computed::Percentage(unit_value),
+        )),
+        _ => Err(()),
+    };
+    value.map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+}
+
+/// The value of an IntersectionObserver's rootMargin property.
+///
+/// Only bare px or percentage values are allowed. Other length units and
+/// calc() values are not allowed.
+///
+/// <https://w3c.github.io/IntersectionObserver/#parse-a-root-margin>
+#[repr(transparent)]
+pub struct IntersectionObserverRootMargin(pub Rect<LengthPercentage>);
+
+impl Parse for IntersectionObserverRootMargin {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use crate::Zero;
+        if input.is_exhausted() {
+            // If there are zero elements in tokens, set tokens to ["0px"].
+            return Ok(IntersectionObserverRootMargin(Rect::all(
+                LengthPercentage::zero(),
+            )));
+        }
+        let rect = Rect::parse_with(context, input, parse_pixel_or_percent)?;
+        Ok(IntersectionObserverRootMargin(rect))
+    }
+}
+
+// Strictly speaking this is not ToCss. It's serializing for DOM. But
+// we can just reuse the infrastructure of this.
+//
+// <https://w3c.github.io/IntersectionObserver/#dom-intersectionobserver-rootmargin>
+impl ToCss for IntersectionObserverRootMargin {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        // We cannot use the ToCss impl of Rect, because that would
+        // merge items when they are equal. We want to list them all.
+        let mut writer = SequenceWriter::new(dest, " ");
+        let rect = &self.0;
+        writer.item(&rect.0)?;
+        writer.item(&rect.1)?;
+        writer.item(&rect.2)?;
+        writer.item(&rect.3)
+    }
+}