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

/// Implementation of Quartz (CoreGraphics) fonts.

extern crate core_foundation;
extern crate core_graphics;
extern crate core_text;

use app_units::Au;
use core_foundation::base::CFIndex;
use core_foundation::data::CFData;
use core_foundation::string::UniChar;
use core_graphics::font::CGGlyph;
use core_graphics::geometry::CGRect;
use core_text::font::CTFont;
use core_text::font_descriptor::{SymbolicTraitAccessors, TraitAccessors};
use core_text::font_descriptor::{kCTFontDefaultOrientation};
use font::FontTableTag;
use font::FractionalPixel;
use font::{FontHandleMethods, FontMetrics, FontTableMethods};
use platform::font_template::FontTemplateData;
use platform::macos::font_context::FontContextHandle;
use std::ptr;
use std::sync::Arc;
use style::computed_values::{font_stretch, font_weight};
use text::glyph::GlyphId;

pub struct FontTable {
    data: CFData,
}

// assumes 72 points per inch, and 96 px per inch
fn px_to_pt(px: f64) -> f64 {
    px / 96. * 72.
}

// assumes 72 points per inch, and 96 px per inch
fn pt_to_px(pt: f64) -> f64 {
    pt / 72. * 96.
}

fn au_from_pt(pt: f64) -> Au {
    Au::from_f64_px(pt_to_px(pt))
}

impl FontTable {
    pub fn wrap(data: CFData) -> FontTable {
        FontTable { data: data }
    }
}

impl FontTableMethods for FontTable {
    fn with_buffer<F>(&self, blk: F) where F: FnOnce(*const u8, usize) {
        blk(self.data.bytes().as_ptr(), self.data.len() as usize);
    }
}

#[derive(Debug)]
pub struct FontHandle {
    pub font_data: Arc<FontTemplateData>,
    pub ctfont: CTFont,
}

impl FontHandleMethods for FontHandle {
    fn new_from_template(_fctx: &FontContextHandle,
                         template: Arc<FontTemplateData>,
                         pt_size: Option<Au>)
                         -> Result<FontHandle, ()> {
        let size = match pt_size {
            Some(s) => s.to_f64_px(),
            None => 0.0
        };
        match template.ctfont(size) {
            Some(ref ctfont) => {
                Ok(FontHandle {
                    font_data: template.clone(),
                    ctfont: ctfont.clone_with_font_size(size),
                })
            }
            None => {
                Err(())
            }
        }
    }

    fn template(&self) -> Arc<FontTemplateData> {
        self.font_data.clone()
    }

    fn family_name(&self) -> String {
        self.ctfont.family_name()
    }

    fn face_name(&self) -> String {
        self.ctfont.face_name()
    }

    fn is_italic(&self) -> bool {
        self.ctfont.symbolic_traits().is_italic()
    }

    fn boldness(&self) -> font_weight::T {
        let normalized = self.ctfont.all_traits().normalized_weight();  // [-1.0, 1.0]
        let normalized = (normalized + 1.0) / 2.0 * 9.0;  // [0.0, 9.0]
        match normalized {
            v if v < 1.0 => font_weight::T::Weight100,
            v if v < 2.0 => font_weight::T::Weight200,
            v if v < 3.0 => font_weight::T::Weight300,
            v if v < 4.0 => font_weight::T::Weight400,
            v if v < 5.0 => font_weight::T::Weight500,
            v if v < 6.0 => font_weight::T::Weight600,
            v if v < 7.0 => font_weight::T::Weight700,
            v if v < 8.0 => font_weight::T::Weight800,
            _ => font_weight::T::Weight900,
        }
    }

    fn stretchiness(&self) -> font_stretch::T {
        let normalized = self.ctfont.all_traits().normalized_width();  // [-1.0, 1.0]
        let normalized = (normalized + 1.0) / 2.0 * 9.0;  // [0.0, 9.0]
        match normalized {
            v if v < 1.0 => font_stretch::T::ultra_condensed,
            v if v < 2.0 => font_stretch::T::extra_condensed,
            v if v < 3.0 => font_stretch::T::condensed,
            v if v < 4.0 => font_stretch::T::semi_condensed,
            v if v < 5.0 => font_stretch::T::normal,
            v if v < 6.0 => font_stretch::T::semi_expanded,
            v if v < 7.0 => font_stretch::T::expanded,
            v if v < 8.0 => font_stretch::T::extra_expanded,
            _ => font_stretch::T::ultra_expanded,
        }
    }

    fn glyph_index(&self, codepoint: char) -> Option<GlyphId> {
        let characters: [UniChar; 1] = [codepoint as UniChar];
        let mut glyphs: [CGGlyph; 1] = [0 as CGGlyph];
        let count: CFIndex = 1;

        let result = self.ctfont.get_glyphs_for_characters(&characters[0],
                                                           &mut glyphs[0],
                                                           count);

        if !result {
            // No glyph for this character
            return None;
        }

        assert!(glyphs[0] != 0); // FIXME: error handling
        return Some(glyphs[0] as GlyphId);
    }

    fn glyph_h_kerning(&self, _first_glyph: GlyphId, _second_glyph: GlyphId)
                        -> FractionalPixel {
        // TODO: Implement on mac
        0.0
    }

    fn glyph_h_advance(&self, glyph: GlyphId) -> Option<FractionalPixel> {
        let glyphs = [glyph as CGGlyph];
        let advance = self.ctfont.get_advances_for_glyphs(kCTFontDefaultOrientation,
                                                          &glyphs[0],
                                                          ptr::null_mut(),
                                                          1);
        Some(advance as FractionalPixel)
    }

    fn metrics(&self) -> FontMetrics {
        let bounding_rect: CGRect = self.ctfont.bounding_box();
        let ascent = self.ctfont.ascent() as f64;
        let descent = self.ctfont.descent() as f64;
        let em_size = Au::from_f64_px(self.ctfont.pt_size() as f64);
        let leading = self.ctfont.leading() as f64;

        let scale = px_to_pt(self.ctfont.pt_size() as f64) / (ascent + descent);
        let line_gap = (ascent + descent + leading + 0.5).floor();

        let max_advance_width = au_from_pt(bounding_rect.size.width as f64);
        let average_advance = self.glyph_index('0')
                                  .and_then(|idx| self.glyph_h_advance(idx))
                                  .map(Au::from_f64_px)
                                  .unwrap_or(max_advance_width);

        let metrics =  FontMetrics {
            underline_size:   au_from_pt(self.ctfont.underline_thickness() as f64),
            // TODO(Issue #201): underline metrics are not reliable. Have to pull out of font table
            // directly.
            //
            // see also: https://bugs.webkit.org/show_bug.cgi?id=16768
            // see also: https://bugreports.qt-project.org/browse/QTBUG-13364
            underline_offset: au_from_pt(self.ctfont.underline_position() as f64),
            strikeout_size:   Au(0), // FIXME(Issue #942)
            strikeout_offset: Au(0), // FIXME(Issue #942)
            leading:          au_from_pt(leading),
            x_height:         au_from_pt(self.ctfont.x_height() as f64),
            em_size:          em_size,
            ascent:           au_from_pt(ascent * scale),
            descent:          au_from_pt(descent * scale),
            max_advance:      max_advance_width,
            average_advance:  average_advance,
            line_gap:         Au::from_f64_px(line_gap),
        };
        debug!("Font metrics (@{} pt): {:?}", self.ctfont.pt_size() as f64, metrics);
        metrics
    }

    fn table_for_tag(&self, tag: FontTableTag) -> Option<Box<FontTable>> {
        let result: Option<CFData> = self.ctfont.get_font_table(tag);
        result.and_then(|data| {
            Some(box FontTable::wrap(data))
        })
    }
}