1 files changed, 150 insertions, 0 deletions
diff --git a/servo/components/style/media_queries/media_list.rs b/servo/components/style/media_queries/media_list.rs
new file mode 100644
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+++ b/servo/components/style/media_queries/media_list.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/. */
+
+//! A media query list:
+//!
+//! https://drafts.csswg.org/mediaqueries/#typedef-media-query-list
+
+use super::{Device, MediaQuery, Qualifier};
+use crate::context::QuirksMode;
+use crate::error_reporting::ContextualParseError;
+use crate::parser::ParserContext;
+use crate::queries::condition::KleeneValue;
+use crate::values::computed;
+use cssparser::{Delimiter, Parser};
+use cssparser::{ParserInput, Token};
+
+/// A type that encapsulates a media query list.
+#[derive(Clone, MallocSizeOf, ToCss, ToShmem)]
+#[css(comma, derive_debug)]
+pub struct MediaList {
+    /// The list of media queries.
+    #[css(iterable)]
+    pub media_queries: Vec<MediaQuery>,
+}
+
+impl MediaList {
+    /// Parse a media query list from CSS.
+    ///
+    /// Always returns a media query list. If any invalid media query is
+    /// found, the media query list is only filled with the equivalent of
+    /// "not all", see:
+    ///
+    /// <https://drafts.csswg.org/mediaqueries/#error-handling>
+    pub fn parse(context: &ParserContext, input: &mut Parser) -> Self {
+        if input.is_exhausted() {
+            return Self::empty();
+        }
+
+        let mut media_queries = vec![];
+        loop {
+            let start_position = input.position();
+            match input.parse_until_before(Delimiter::Comma, |i| MediaQuery::parse(context, i)) {
+                Ok(mq) => {
+                    media_queries.push(mq);
+                },
+                Err(err) => {
+                    media_queries.push(MediaQuery::never_matching());
+                    let location = err.location;
+                    let error = ContextualParseError::InvalidMediaRule(
+                        input.slice_from(start_position),
+                        err,
+                    );
+                    context.log_css_error(location, error);
+                },
+            }
+
+            match input.next() {
+                Ok(&Token::Comma) => {},
+                Ok(_) => unreachable!(),
+                Err(_) => break,
+            }
+        }
+
+        MediaList { media_queries }
+    }
+
+    /// Create an empty MediaList.
+    pub fn empty() -> Self {
+        MediaList {
+            media_queries: vec![],
+        }
+    }
+
+    /// Evaluate a whole `MediaList` against `Device`.
+    pub fn evaluate(&self, device: &Device, quirks_mode: QuirksMode) -> bool {
+        // Check if it is an empty media query list or any queries match.
+        // https://drafts.csswg.org/mediaqueries-4/#mq-list
+        if self.media_queries.is_empty() {
+            return true;
+        }
+
+        computed::Context::for_media_query_evaluation(device, quirks_mode, |context| {
+            self.media_queries.iter().any(|mq| {
+                let mut query_match = if mq.media_type.matches(device.media_type()) {
+                    mq.condition
+                        .as_ref()
+                        .map_or(KleeneValue::True, |c| c.matches(context))
+                } else {
+                    KleeneValue::False
+                };
+
+                // Apply the logical NOT qualifier to the result
+                if matches!(mq.qualifier, Some(Qualifier::Not)) {
+                    query_match = !query_match;
+                }
+                query_match.to_bool(/* unknown = */ false)
+            })
+        })
+    }
+
+    /// Whether this `MediaList` contains no media queries.
+    pub fn is_empty(&self) -> bool {
+        self.media_queries.is_empty()
+    }
+
+    /// Whether this `MediaList` depends on the viewport size.
+    pub fn is_viewport_dependent(&self) -> bool {
+        self.media_queries.iter().any(|q| q.is_viewport_dependent())
+    }
+
+    /// Append a new media query item to the media list.
+    /// <https://drafts.csswg.org/cssom/#dom-medialist-appendmedium>
+    ///
+    /// Returns true if added, false if fail to parse the medium string.
+    pub fn append_medium(&mut self, context: &ParserContext, new_medium: &str) -> bool {
+        let mut input = ParserInput::new(new_medium);
+        let mut parser = Parser::new(&mut input);
+        let new_query = match MediaQuery::parse(&context, &mut parser) {
+            Ok(query) => query,
+            Err(_) => {
+                return false;
+            },
+        };
+        // This algorithm doesn't actually matches the current spec,
+        // but it matches the behavior of Gecko and Edge.
+        // See https://github.com/w3c/csswg-drafts/issues/697
+        self.media_queries.retain(|query| query != &new_query);
+        self.media_queries.push(new_query);
+        true
+    }
+
+    /// Delete a media query from the media list.
+    /// <https://drafts.csswg.org/cssom/#dom-medialist-deletemedium>
+    ///
+    /// Returns true if found and deleted, false otherwise.
+    pub fn delete_medium(&mut self, context: &ParserContext, old_medium: &str) -> bool {
+        let mut input = ParserInput::new(old_medium);
+        let mut parser = Parser::new(&mut input);
+        let old_query = match MediaQuery::parse(context, &mut parser) {
+            Ok(query) => query,
+            Err(_) => {
+                return false;
+            },
+        };
+        let old_len = self.media_queries.len();
+        self.media_queries.retain(|query| query != &old_query);
+        old_len != self.media_queries.len()
+    }
+}