servo/components/gfx/platform/macos/font_template.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/. */

use app_units::Au;
use core_graphics::data_provider::CGDataProvider;
use core_graphics::font::CGFont;
use core_text;
use core_text::font::CTFont;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
use serde::de::{Error, Visitor};
use servo_atoms::Atom;
use servo_url::ServoUrl;
use std::borrow::ToOwned;
use std::collections::HashMap;
use std::fmt;
use std::fs::File;
use std::io::{Read, Error as IoError};
use std::ops::Deref;
use std::sync::Mutex;

/// Platform specific font representation for mac.
/// The identifier is a PostScript font name. The
/// CTFont object is cached here for use by the
/// paint functions that create CGFont references.
#[derive(Deserialize, Serialize, Debug)]
pub struct FontTemplateData {
    /// The `CTFont` object, if present. This is cached here so that we don't have to keep creating
    /// `CTFont` instances over and over. It can always be recreated from the `identifier` and/or
    /// `font_data` fields.
    ///
    /// When sending a `FontTemplateData` instance across processes, this will be cleared out on
    /// the other side, because `CTFont` instances cannot be sent across processes. This is
    /// harmless, however, because it can always be recreated.
    ctfont: CachedCTFont,

    pub identifier: Atom,
    pub font_data: Option<Vec<u8>>
}

unsafe impl Send for FontTemplateData {}
unsafe impl Sync for FontTemplateData {}

impl FontTemplateData {
    pub fn new(identifier: Atom, font_data: Option<Vec<u8>>) -> Result<FontTemplateData, IoError> {
        Ok(FontTemplateData {
            ctfont: CachedCTFont(Mutex::new(HashMap::new())),
            identifier: identifier.to_owned(),
            font_data: font_data
        })
    }

    /// Retrieves the Core Text font instance, instantiating it if necessary.
    pub fn ctfont(&self, pt_size: f64) -> Option<CTFont> {
        let mut ctfonts = self.ctfont.lock().unwrap();
        let pt_size_key = Au::from_f64_px(pt_size);
        if !ctfonts.contains_key(&pt_size_key) {
            // If you pass a zero font size to one of the Core Text APIs, it'll replace it with
            // 12.0. We don't want that! (Issue #10492.)
            let clamped_pt_size = pt_size.max(0.01);
            let ctfont = match self.font_data {
                Some(ref bytes) => {
                    let fontprov = CGDataProvider::from_buffer(bytes);
                    let cgfont_result = CGFont::from_data_provider(fontprov);
                    match cgfont_result {
                        Ok(cgfont) => {
                            Some(core_text::font::new_from_CGFont(&cgfont, clamped_pt_size))
                        }
                        Err(_) => None
                    }
                }
                None => core_text::font::new_from_name(&*self.identifier, clamped_pt_size).ok(),
            };
            if let Some(ctfont) = ctfont {
                ctfonts.insert(pt_size_key, ctfont);
            }
        }
        ctfonts.get(&pt_size_key).map(|ctfont| (*ctfont).clone())
    }

    /// Returns a clone of the data in this font. This may be a hugely expensive
    /// operation (depending on the platform) which performs synchronous disk I/O
    /// and should never be done lightly.
    pub fn bytes(&self) -> Vec<u8> {
        if let Some(font_data) = self.bytes_if_in_memory() {
            return font_data;
        }

        let path = ServoUrl::parse(&*self.ctfont(0.0)
                                    .expect("No Core Text font available!")
                                    .url()
                                    .expect("No URL for Core Text font!")
                                    .get_string()
                                    .to_string()).expect("Couldn't parse Core Text font URL!")
                                                 .as_url().unwrap().to_file_path()
                                                 .expect("Core Text font didn't name a path!");
        let mut bytes = Vec::new();
        File::open(path).expect("Couldn't open font file!").read_to_end(&mut bytes).unwrap();
        bytes
    }

    /// Returns a clone of the bytes in this font if they are in memory. This function never
    /// performs disk I/O.
    pub fn bytes_if_in_memory(&self) -> Option<Vec<u8>> {
        self.font_data.clone()
    }

    /// Returns the native font that underlies this font template, if applicable.
    pub fn native_font(&self) -> Option<CGFont> {
        self.ctfont(0.0).map(|ctfont| ctfont.copy_to_CGFont())
    }
}

#[derive(Debug)]
pub struct CachedCTFont(Mutex<HashMap<Au, CTFont>>);

impl Deref for CachedCTFont {
    type Target = Mutex<HashMap<Au, CTFont>>;
    fn deref(&self) -> &Mutex<HashMap<Au, CTFont>> {
        &self.0
    }
}

impl Serialize for CachedCTFont {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer {
        serializer.serialize_none()
    }
}

impl Deserialize for CachedCTFont {
    fn deserialize<D>(deserializer: D) -> Result<CachedCTFont, D::Error>
                      where D: Deserializer {
        struct NoneOptionVisitor;

        impl Visitor for NoneOptionVisitor {
            type Value = CachedCTFont;

            fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
                write!(fmt, "none")
            }

            #[inline]
            fn visit_none<E>(self) -> Result<CachedCTFont, E> where E: Error {
                Ok(CachedCTFont(Mutex::new(HashMap::new())))
            }
        }

        deserializer.deserialize_option(NoneOptionVisitor)
    }
}