style/url/
servo.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! Servo-specific logic for CSS url() values.
6
7use crate::derives::*;
8use crate::parser::ParserContext;
9use crate::stylesheets::CorsMode;
10use crate::values::computed::{Context, ToComputedValue};
11use servo_arc::Arc;
12use std::fmt::{self, Write};
13use std::ops::Deref;
14use style_traits::{CssWriter, ToCss};
15use to_shmem::{SharedMemoryBuilder, ToShmem};
16use url::Url;
17
18/// A CSS url() value for servo.
19///
20/// Servo eagerly resolves SpecifiedUrls, which it can then take advantage of
21/// when computing values. In contrast, Gecko uses a different URL backend, so
22/// eagerly resolving with rust-url would be duplicated work.
23///
24/// However, this approach is still not necessarily optimal: See
25/// <https://bugzilla.mozilla.org/show_bug.cgi?id=1347435#c6>
26#[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize, SpecifiedValueInfo)]
27#[css(function = "url")]
28#[repr(C)]
29pub struct CssUrl(#[ignore_malloc_size_of = "Arc"] pub Arc<CssUrlData>);
30
31/// Data shared between CssUrls.
32///
33#[derive(Debug, Deserialize, MallocSizeOf, Serialize, SpecifiedValueInfo)]
34#[repr(C)]
35pub struct CssUrlData {
36    /// The original URI. This might be optional since we may insert computed
37    /// values of images into the cascade directly, and we don't bother to
38    /// convert their serialization.
39    ///
40    /// Refcounted since cloning this should be cheap and data: uris can be
41    /// really large.
42    #[ignore_malloc_size_of = "Arc"]
43    original: Option<Arc<String>>,
44
45    /// The resolved value for the url, if valid.
46    #[ignore_malloc_size_of = "Arc"]
47    resolved: Option<Arc<Url>>,
48}
49
50impl ToShmem for CssUrl {
51    fn to_shmem(&self, _builder: &mut SharedMemoryBuilder) -> to_shmem::Result<Self> {
52        unimplemented!("If servo wants to share stylesheets across processes, ToShmem for Url must be implemented");
53    }
54}
55
56impl Deref for CssUrl {
57    type Target = CssUrlData;
58    fn deref(&self) -> &Self::Target {
59        &self.0
60    }
61}
62
63impl CssUrl {
64    /// Try to parse a URL from a string value that is a valid CSS token for a
65    /// URL.
66    ///
67    /// FIXME(emilio): Should honor CorsMode.
68    pub(super) fn new_from_string(
69        url: String,
70        context: &ParserContext,
71        _cors_mode: CorsMode,
72    ) -> Self {
73        let serialization = Arc::new(url);
74        // Per https://drafts.csswg.org/css-values-4/#url-empty
75        // If the original url is empty, then the resolved url is considered invalid.
76        let resolved = (!serialization.is_empty())
77            .then(|| context.url_data.0.join(&serialization))
78            .and_then(Result::ok)
79            .map(Arc::new);
80        CssUrl(Arc::new(CssUrlData {
81            original: Some(serialization),
82            resolved: resolved,
83        }))
84    }
85
86    /// Returns true if the URL is definitely invalid. For Servo URLs, we can
87    /// use its |resolved| status.
88    pub fn is_invalid(&self) -> bool {
89        self.resolved.is_none()
90    }
91
92    /// Returns true if this URL looks like a fragment.
93    /// See https://drafts.csswg.org/css-values/#local-urls
94    ///
95    /// Since Servo currently stores resolved URLs, this is hard to implement. We
96    /// either need to change servo to lazily resolve (like Gecko), or note this
97    /// information in the tokenizer.
98    pub fn is_fragment(&self) -> bool {
99        error!("Can't determine whether the url is a fragment.");
100        false
101    }
102
103    /// Returns the resolved url if it was valid.
104    pub fn url(&self) -> Option<&Arc<Url>> {
105        self.resolved.as_ref()
106    }
107
108    /// Return the resolved url as string, or the empty string if it's invalid.
109    ///
110    /// TODO(emilio): Should we return the original one if needed?
111    pub fn as_str(&self) -> &str {
112        match self.resolved {
113            Some(ref url) => url.as_str(),
114            None => "",
115        }
116    }
117
118    /// Creates an already specified url value from an already resolved URL
119    /// for insertion in the cascade.
120    pub fn for_cascade(url: Arc<::url::Url>) -> Self {
121        CssUrl(Arc::new(CssUrlData {
122            original: None,
123            resolved: Some(url),
124        }))
125    }
126
127    /// Gets a new url from a string for unit tests.
128    pub fn new_for_testing(url: &str) -> Self {
129        CssUrl(Arc::new(CssUrlData {
130            original: Some(Arc::new(url.into())),
131            resolved: (!url.is_empty())
132                .then(|| ::url::Url::parse(url))
133                .and_then(Result::ok)
134                .map(Arc::new),
135        }))
136    }
137}
138
139impl PartialEq for CssUrl {
140    fn eq(&self, other: &Self) -> bool {
141        // TODO(emilio): maybe we care about equality of the specified values if
142        // present? Seems not.
143        self.resolved == other.resolved
144    }
145}
146
147impl Eq for CssUrl {}
148
149impl ToCss for CssUrl {
150    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
151    where
152        W: Write,
153    {
154        let string = match self.0.original {
155            Some(ref original) => &**original,
156            None => match self.resolved {
157                Some(ref url) => url.as_str(),
158                // This can only happen if the url wasn't specified by the
159                // user *and* it's an invalid url that has been transformed
160                // back to specified value via the "uncompute" functionality.
161                None => "about:invalid",
162            },
163        };
164
165        dest.write_str("url(")?;
166        string.to_css(dest)?;
167        dest.write_char(')')
168    }
169}
170
171/// A specified url() value for servo.
172pub type SpecifiedUrl = CssUrl;
173
174impl ToComputedValue for SpecifiedUrl {
175    type ComputedValue = ComputedUrl;
176
177    // If we can't resolve the URL from the specified one, we fall back to the original
178    // but still return it as a ComputedUrl::Invalid
179    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
180        match self.resolved {
181            Some(ref url) => ComputedUrl::Valid(url.clone()),
182            None => match self.original {
183                Some(ref url) => ComputedUrl::Invalid(url.clone()),
184                None => {
185                    unreachable!("Found specified url with neither resolved or original URI!");
186                },
187            },
188        }
189    }
190
191    fn from_computed_value(computed: &ComputedUrl) -> Self {
192        let data = match *computed {
193            ComputedUrl::Valid(ref url) => CssUrlData {
194                original: None,
195                resolved: Some(url.clone()),
196            },
197            ComputedUrl::Invalid(ref url) => CssUrlData {
198                original: Some(url.clone()),
199                resolved: None,
200            },
201        };
202        CssUrl(Arc::new(data))
203    }
204}
205
206/// The computed value of a CSS `url()`, resolved relative to the stylesheet URL.
207#[derive(Clone, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize)]
208pub enum ComputedUrl {
209    /// The `url()` was invalid or it wasn't specified by the user.
210    Invalid(#[ignore_malloc_size_of = "Arc"] Arc<String>),
211    /// The resolved `url()` relative to the stylesheet URL.
212    Valid(#[ignore_malloc_size_of = "Arc"] Arc<Url>),
213}
214
215impl ComputedUrl {
216    /// Returns the resolved url if it was valid.
217    pub fn url(&self) -> Option<&Arc<Url>> {
218        match *self {
219            ComputedUrl::Valid(ref url) => Some(url),
220            _ => None,
221        }
222    }
223}
224
225impl ToCss for ComputedUrl {
226    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
227    where
228        W: Write,
229    {
230        let string = match *self {
231            ComputedUrl::Valid(ref url) => url.as_str(),
232            ComputedUrl::Invalid(ref invalid_string) => invalid_string,
233        };
234
235        dest.write_str("url(")?;
236        string.to_css(dest)?;
237        dest.write_char(')')
238    }
239}
style/url/servo.rs

style/url/
servo.rs
