servo/components/style/media_queries.rs

/* 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 http://mozilla.org/MPL/2.0/. */

//! [Media queries][mq].
//!
//! [mq]: https://drafts.csswg.org/mediaqueries/

use Atom;
use context::QuirksMode;
use cssparser::{Delimiter, Parser};
use cssparser::{Token, ParserInput};
use error_reporting::{ContextualParseError, ParseErrorReporter};
use parser::{ParserContext, ParserErrorContext};
use selectors::parser::SelectorParseErrorKind;
use std::fmt::{self, Write};
use str::string_as_ascii_lowercase;
use style_traits::{CssWriter, ToCss, ParseError, StyleParseErrorKind};
use values::CustomIdent;

#[cfg(feature = "servo")]
pub use servo::media_queries::{Device, Expression};
#[cfg(feature = "gecko")]
pub use gecko::media_queries::{Device, Expression};

/// A type that encapsulates a media query list.
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
#[css(comma)]
#[derive(Clone, Debug, ToCss)]
pub struct MediaList {
    /// The list of media queries.
    #[css(iterable)]
    pub media_queries: Vec<MediaQuery>,
}

impl MediaList {
    /// Create an empty MediaList.
    pub fn empty() -> Self {
        MediaList { media_queries: vec![] }
    }
}

/// <https://drafts.csswg.org/mediaqueries/#mq-prefix>
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
#[derive(Clone, Copy, Debug, Eq, PartialEq, ToCss)]
pub enum Qualifier {
    /// Hide a media query from legacy UAs:
    /// <https://drafts.csswg.org/mediaqueries/#mq-only>
    Only,
    /// Negate a media query:
    /// <https://drafts.csswg.org/mediaqueries/#mq-not>
    Not,
}

/// A [media query][mq].
///
/// [mq]: https://drafts.csswg.org/mediaqueries/
#[derive(Clone, Debug, PartialEq)]
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub struct MediaQuery {
    /// The qualifier for this query.
    pub qualifier: Option<Qualifier>,
    /// The media type for this query, that can be known, unknown, or "all".
    pub media_type: MediaQueryType,
    /// The set of expressions that this media query contains.
    pub expressions: Vec<Expression>,
}

impl MediaQuery {
    /// Return a media query that never matches, used for when we fail to parse
    /// a given media query.
    fn never_matching() -> Self {
        Self {
            qualifier: Some(Qualifier::Not),
            media_type: MediaQueryType::All,
            expressions: vec![],
        }
    }
}

impl ToCss for MediaQuery {
    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    where
        W: Write,
    {
        if let Some(qual) = self.qualifier {
            qual.to_css(dest)?;
            dest.write_char(' ')?;
        }

        match self.media_type {
            MediaQueryType::All => {
                // We need to print "all" if there's a qualifier, or there's
                // just an empty list of expressions.
                //
                // Otherwise, we'd serialize media queries like "(min-width:
                // 40px)" in "all (min-width: 40px)", which is unexpected.
                if self.qualifier.is_some() || self.expressions.is_empty() {
                    dest.write_str("all")?;
                }
            },
            MediaQueryType::Concrete(MediaType(ref desc)) => desc.to_css(dest)?,
        }

        if self.expressions.is_empty() {
            return Ok(());
        }

        if self.media_type != MediaQueryType::All || self.qualifier.is_some() {
            dest.write_str(" and ")?;
        }

        self.expressions[0].to_css(dest)?;

        for expr in self.expressions.iter().skip(1) {
            dest.write_str(" and ")?;
            expr.to_css(dest)?;
        }
        Ok(())
    }
}

/// <http://dev.w3.org/csswg/mediaqueries-3/#media0>
#[derive(Clone, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub enum MediaQueryType {
    /// A media type that matches every device.
    All,
    /// A specific media type.
    Concrete(MediaType),
}

impl MediaQueryType {
    fn parse(ident: &str) -> Result<Self, ()> {
        match_ignore_ascii_case! { ident,
            "all" => return Ok(MediaQueryType::All),
            _ => (),
        };

        // If parseable, accept this type as a concrete type.
        MediaType::parse(ident).map(MediaQueryType::Concrete)
    }

    fn matches(&self, other: MediaType) -> bool {
        match *self {
            MediaQueryType::All => true,
            MediaQueryType::Concrete(ref known_type) => *known_type == other,
        }
    }
}

/// <https://drafts.csswg.org/mediaqueries/#media-types>
#[derive(Clone, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub struct MediaType(pub CustomIdent);

impl MediaType {
    /// The `screen` media type.
    pub fn screen() -> Self {
        MediaType(CustomIdent(atom!("screen")))
    }

    /// The `print` media type.
    pub fn print() -> Self {
        MediaType(CustomIdent(atom!("print")))
    }

    fn parse(name: &str) -> Result<Self, ()> {
        // From https://drafts.csswg.org/mediaqueries/#mq-syntax:
        //
        //   The <media-type> production does not include the keywords not, or, and, and only.
        //
        // Here we also perform the to-ascii-lowercase part of the serialization
        // algorithm: https://drafts.csswg.org/cssom/#serializing-media-queries
        match_ignore_ascii_case! { name,
            "not" | "or" | "and" | "only" => Err(()),
            _ => Ok(MediaType(CustomIdent(Atom::from(string_as_ascii_lowercase(name))))),
        }
    }
}
impl MediaQuery {
    /// Parse a media query given css input.
    ///
    /// Returns an error if any of the expressions is unknown.
    pub fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
                         -> Result<MediaQuery, ParseError<'i>> {
        let mut expressions = vec![];

        let qualifier = if input.try(|input| input.expect_ident_matching("only")).is_ok() {
            Some(Qualifier::Only)
        } else if input.try(|input| input.expect_ident_matching("not")).is_ok() {
            Some(Qualifier::Not)
        } else {
            None
        };

        let media_type = match input.try(|i| i.expect_ident_cloned()) {
            Ok(ident) => {
                MediaQueryType::parse(&*ident)
                    .map_err(|()| {
                        input.new_custom_error(
                            SelectorParseErrorKind::UnexpectedIdent(ident.clone())
                        )
                    })?
            }
            Err(_) => {
                // Media type is only optional if qualifier is not specified.
                if qualifier.is_some() {
                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
                }

                // Without a media type, require at least one expression.
                expressions.push(Expression::parse(context, input)?);

                MediaQueryType::All
            }
        };

        // Parse any subsequent expressions
        loop {
            if input.try(|input| input.expect_ident_matching("and")).is_err() {
                return Ok(MediaQuery { qualifier, media_type, expressions })
            }
            expressions.push(Expression::parse(context, input)?)
        }
    }
}

/// 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_media_query_list<R>(
    context: &ParserContext,
    input: &mut Parser,
    error_reporter: &R,
) -> MediaList
where
    R: ParseErrorReporter,
{
    if input.is_exhausted() {
        return MediaList::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);
                let error_context = ParserErrorContext { error_reporter };
                context.log_css_error(&error_context, location, error);
            },
        }

        match input.next() {
            Ok(&Token::Comma) => {},
            Ok(_) => unreachable!(),
            Err(_) => break,
        }
    }

    MediaList {
        media_queries: media_queries,
    }
}

impl MediaList {
    /// 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 (OR condition)
        // https://drafts.csswg.org/mediaqueries-4/#mq-list
        self.media_queries.is_empty() || self.media_queries.iter().any(|mq| {
            let media_match = mq.media_type.matches(device.media_type());

            // Check if all conditions match (AND condition)
            let query_match =
                media_match &&
                mq.expressions.iter()
                    .all(|expression| expression.matches(&device, quirks_mode));

            // Apply the logical NOT qualifier to the result
            match mq.qualifier {
                Some(Qualifier::Not) => !query_match,
                _ => query_match,
            }
        })
    }

    /// Whether this `MediaList` contains no media queries.
    pub fn is_empty(&self) -> bool {
        self.media_queries.is_empty()
    }

    /// 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()
    }
}