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// font-kit/src/loader.rs
//
// Copyright © 2018 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Provides a common interface to the platform-specific API that loads, parses, and rasterizes
//! fonts.

use euclid::{Point2D, Rect, Vector2D};
use lyon_path::builder::PathBuilder;
use std::fs::File;
use std::path::Path;
use std::sync::Arc;

use canvas::{Canvas, RasterizationOptions};
use error::{FontLoadingError, GlyphLoadingError};
use file_type::FileType;
use handle::Handle;
use hinting::HintingOptions;
use metrics::Metrics;
use properties::Properties;

/// Provides a common interface to the platform-specific API that loads, parses, and rasterizes
/// fonts.
pub trait Loader: Clone + Sized {
    /// The handle that the API natively uses to represent a font.
    type NativeFont;

    /// Loads a font from raw font data (the contents of a `.ttf`/`.otf`/etc. file).
    ///
    /// If the data represents a collection (`.ttc`/`.otc`/etc.), `font_index` specifies the index
    /// of the font to load from it. If the data represents a single font, pass 0 for `font_index`.
    fn from_bytes(font_data: Arc<Vec<u8>>, font_index: u32) -> Result<Self, FontLoadingError>;

    /// Loads a font from a `.ttf`/`.otf`/etc. file.
    ///
    /// If the file is a collection (`.ttc`/`.otc`/etc.), `font_index` specifies the index of the
    /// font to load from it. If the file represents a single font, pass 0 for `font_index`.
    fn from_file(file: &mut File, font_index: u32) -> Result<Self, FontLoadingError>;

    /// Loads a font from the path to a `.ttf`/`.otf`/etc. file.
    ///
    /// If the file is a collection (`.ttc`/`.otc`/etc.), `font_index` specifies the index of the
    /// font to load from it. If the file represents a single font, pass 0 for `font_index`.
    fn from_path<P>(path: P, font_index: u32) -> Result<Self, FontLoadingError>
                    where P: AsRef<Path> {
        Loader::from_file(&mut try!(File::open(path)), font_index)
    }

    /// Creates a font from a native API handle.
    unsafe fn from_native_font(native_font: Self::NativeFont) -> Self;

    /// Loads the font pointed to by a handle.
    fn from_handle(handle: &Handle) -> Result<Self, FontLoadingError> {
        match *handle {
            Handle::Memory {
                ref bytes,
                font_index,
            } => Self::from_bytes((*bytes).clone(), font_index),
            Handle::Path {
                ref path,
                font_index,
            } => Self::from_path(path, font_index),
        }
    }

    /// Determines whether a blob of raw font data represents a supported font, and, if so, what
    /// type of font it is.
    fn analyze_bytes(font_data: Arc<Vec<u8>>) -> Result<FileType, FontLoadingError>;

    /// Determines whether a file represents a supported font, and, if so, what type of font it is.
    fn analyze_file(file: &mut File) -> Result<FileType, FontLoadingError>;

    /// Determines whether a path points to a supported font, and, if so, what type of font it is.
    #[inline]
    fn analyze_path<P>(path: P) -> Result<FileType, FontLoadingError> where P: AsRef<Path> {
        <Self as Loader>::analyze_file(&mut try!(File::open(path)))
    }

    /// Returns the wrapped native font handle.
    fn native_font(&self) -> Self::NativeFont;

    /// Returns the PostScript name of the font. This should be globally unique.
    fn postscript_name(&self) -> Option<String>;

    /// Returns the full name of the font (also known as "display name" on macOS).
    fn full_name(&self) -> String;

    /// Returns the name of the font family.
    fn family_name(&self) -> String;

    /// Returns true if and only if the font is monospace (fixed-width).
    fn is_monospace(&self) -> bool;

    /// Returns the values of various font properties, corresponding to those defined in CSS.
    fn properties(&self) -> Properties;

    /// Returns the number of glyphs in the font.
    ///
    /// Glyph IDs range from 0 inclusive to this value exclusive.
    fn glyph_count(&self) -> u32;

    /// Returns the usual glyph ID for a Unicode character.
    ///
    /// Be careful with this function; typographically correct character-to-glyph mapping must be
    /// done using a *shaper* such as HarfBuzz. This function is only useful for best-effort simple
    /// use cases like "what does character X look like on its own".
    fn glyph_for_char(&self, character: char) -> Option<u32>;

    /// Sends the vector path for a glyph to a path builder.
    ///
    /// If `hinting_mode` is not None, this function performs grid-fitting as requested before
    /// sending the hinding outlines to the builder.
    ///
    /// TODO(pcwalton): What should we do for bitmap glyphs?
    fn outline<B>(&self, glyph_id: u32, hinting_mode: HintingOptions, path_builder: &mut B)
                  -> Result<(), GlyphLoadingError>
                  where B: PathBuilder;

    /// Returns the boundaries of a glyph in font units.
    fn typographic_bounds(&self, glyph_id: u32) -> Result<Rect<f32>, GlyphLoadingError>;

    /// Returns the distance from the origin of the glyph with the given ID to the next, in font
    /// units.
    fn advance(&self, glyph_id: u32) -> Result<Vector2D<f32>, GlyphLoadingError>;

    /// Returns the amount that the given glyph should be displaced from the origin.
    fn origin(&self, glyph_id: u32) -> Result<Point2D<f32>, GlyphLoadingError>;

    /// Retrieves various metrics that apply to the entire font.
    fn metrics(&self) -> Metrics;

    /// Returns a handle to this font, if possible.
    ///
    /// This is useful if you want to open the font with a different loader.
    fn handle(&self) -> Option<Handle> {
        // FIXME(pcwalton): This doesn't handle font collections!
        self.copy_font_data().map(|font_data| Handle::from_memory(font_data, 0))
    }

    /// Attempts to return the raw font data (contents of the font file).
    ///
    /// If this font is a member of a collection, this function returns the data for the entire
    /// collection.
    fn copy_font_data(&self) -> Option<Arc<Vec<u8>>>;

    /// Returns true if and only if the font loader can perform hinting in the requested way.
    ///
    /// Some APIs support only rasterizing glyphs with hinting, not retriving hinted outlines. If
    /// `for_rasterization` is false, this function returns true if and only if the loader supports
    /// retrieval of hinted *outlines*. If `for_rasterization` is true, this function returns true
    /// if and only if the loader supports *rasterizing* hinted glyphs.
    fn supports_hinting_options(&self, hinting_options: HintingOptions, for_rasterization: bool)
                                -> bool;

    /// Returns the pixel boundaries that the glyph will take up when rendered using this loader's
    /// rasterizer at the given size and origin.
    fn raster_bounds(&self,
                     glyph_id: u32,
                     point_size: f32,
                     origin: &Point2D<f32>,
                     _: HintingOptions,
                     _: RasterizationOptions)
                     -> Result<Rect<i32>, GlyphLoadingError> {
        let typographic_bounds = try!(self.typographic_bounds(glyph_id));
        let typographic_raster_bounds = typographic_bounds * point_size /
            self.metrics().units_per_em as f32;
        Ok(typographic_raster_bounds.translate(&origin.to_vector()).round_out().to_i32())
    }

    /// Rasterizes a glyph to a canvas with the given size and origin.
    ///
    /// Format conversion will be performed if the canvas format does not match the rasterization
    /// options. For example, if bilevel (black and white) rendering is requested to an RGBA
    /// surface, this function will automatically convert the 1-bit raster image to the 32-bit
    /// format of the canvas. Note that this may result in a performance penalty, depending on the
    /// loader.
    ///
    /// If `hinting_options` is not None, the requested grid fitting is performed.
    fn rasterize_glyph(&self,
                       canvas: &mut Canvas,
                       glyph_id: u32,
                       point_size: f32,
                       origin: &Point2D<f32>,
                       hinting_options: HintingOptions,
                       rasterization_options: RasterizationOptions)
                       -> Result<(), GlyphLoadingError>;
}