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use super::cache::CacheKey;
use super::internal::{raw_data, RawFont};
use super::Tag;
/// Reference to the content of a font file.
#[derive(Copy, Clone)]
pub struct FontDataRef<'a> {
data: &'a [u8],
len: usize,
}
impl<'a> FontDataRef<'a> {
/// Creates font data from the specified bytes. Returns `None` if the bytes
/// cannot trivially be determined to represent a font.
pub fn new(data: &'a [u8]) -> Option<Self> {
if !raw_data::is_font(data, 0) && !raw_data::is_collection(data) {
None
} else {
Some(Self {
data,
len: raw_data::count(data) as usize,
})
}
}
/// Returns true if the data represents a font collection.
pub fn is_collection(&self) -> bool {
raw_data::is_collection(self.data)
}
/// Returns the underlying data.
pub fn data(&self) -> &'a [u8] {
self.data
}
/// Returns the number of available fonts.
pub fn len(&self) -> usize {
self.len
}
/// Returns true if there are no available fonts.
pub fn is_empty(&self) -> bool {
self.len == 0
}
/// Returns the font at the specified index.
pub fn get(&self, index: usize) -> Option<FontRef<'a>> {
FontRef::from_offset(self.data, raw_data::offset(self.data, index as u32)?)
}
/// Returns an iterator over the available fonts.
pub fn fonts(&self) -> Fonts<'a> {
Fonts {
data: *self,
pos: 0,
}
}
}
/// Reference to a font.
///
/// This struct encapsulates the data required to access font resources and
/// uniquely identify the font in various caches. Font files can be organized
/// into collections of multiple fonts, so along with a reference to the actual
/// content of the file, we also store a byte offset to the header of the
/// selected font (although most fonts are not collections so this is almost always
/// zero). Note that internal references in the font are stored relative to the
/// base of the file, so the entire file must be kept in memory and it is an error
/// to slice the data at the offset.
///
/// # Getting started
/// As a primer, let's write a function to read a font file, construct a font reference
/// and print the [`Attributes`](super::Attributes) and all of the associated
/// [`LocalizedString`](super::LocalizedString)s (including names, copyright information
/// and other metadata).
///
/// ```
/// fn print_localized_strings(font_path: &str) -> Option<()> {
/// use swash::FontRef;
/// // Read the full font file
/// let font_data = std::fs::read(font_path).ok()?;
/// // Create a font reference for the first font in the file
/// let font = FontRef::from_index(&font_data, 0)?;
/// // Print the font attributes (stretch, weight and style)
/// println!("{}", font.attributes());
/// // Iterate through the localized strings
/// for string in font.localized_strings() {
/// // Print the string identifier and the actual value
/// println!("[{:?}] {}", string.id(), string.to_string());
/// }
/// Some(())
/// }
/// ```
///
/// # Owning your fonts
/// The [`FontRef`] struct is designed to be agnostic with regard to the font management
/// policy of higher level crates and applications, and as such, contains borrowed
/// data and is intended to be used as a transient resource. If you're using this
/// library, you'll likely want to create your own type to represent a font.
/// Regardless of the complexity of your management strategy, the basic pattern remains
/// the same, so we'll build a simple `Font` struct here that can load fonts from a
/// file using a basic `Vec<u8>` as a backing store.
/// ```
/// use swash::{Attributes, CacheKey, Charmap, FontRef};
///
/// pub struct Font {
/// // Full content of the font file
/// data: Vec<u8>,
/// // Offset to the table directory
/// offset: u32,
/// // Cache key
/// key: CacheKey,
/// }
///
/// impl Font {
/// pub fn from_file(path: &str, index: usize) -> Option<Self> {
/// // Read the full font file
/// let data = std::fs::read(path).ok()?;
/// // Create a temporary font reference for the first font in the file.
/// // This will do some basic validation, compute the necessary offset
/// // and generate a fresh cache key for us.
/// let font = FontRef::from_index(&data, index)?;
/// let (offset, key) = (font.offset, font.key);
/// // Return our struct with the original file data and copies of the
/// // offset and key from the font reference
/// Some(Self { data, offset, key })
/// }
///
/// // As a convenience, you may want to forward some methods.
/// pub fn attributes(&self) -> Attributes {
/// self.as_ref().attributes()
/// }
///
/// pub fn charmap(&self) -> Charmap {
/// self.as_ref().charmap()
/// }
///
/// // Create the transient font reference for accessing this crate's
/// // functionality.
/// pub fn as_ref(&self) -> FontRef {
/// // Note that you'll want to initialize the struct directly here as
/// // using any of the FontRef constructors will generate a new key which,
/// // while completely safe, will nullify the performance optimizations of
/// // the caching mechanisms used in this crate.
/// FontRef {
/// data: &self.data,
/// offset: self.offset,
/// key: self.key
/// }
/// }
/// }
/// ```
/// In the example above, it's trivial to replace the `Vec<u8>` with an
/// `Rc<Vec<u8>>` for a reference counted version or an `Arc<Vec<u8>>` for fonts
/// that are shareable across threads. You may also consider memory mapping
/// your font data, particularly for larger fonts (hello Apple Color Emoji!).
///
#[derive(Copy, Clone)]
pub struct FontRef<'a> {
/// Full content of a file containing the font.
pub data: &'a [u8],
/// Offset to the table directory of the font.
pub offset: u32,
/// Key for identifying a font in various caches.
pub key: CacheKey,
}
impl<'a> FontRef<'a> {
/// Creates a new font from the specified font data and the index of the
/// desired font. Returns `None` if the data does not represent a font file
/// or the index is out of bounds.
pub fn from_index(data: &'a [u8], index: usize) -> Option<Self> {
FontDataRef::new(data)?.get(index)
}
/// Creates a new font from the specified font data and offset to the
/// table directory. Returns `None` if the offset is out of bounds or the
/// data at the offset does not represent a table directory.
pub fn from_offset(data: &'a [u8], offset: u32) -> Option<Self> {
if !raw_data::is_font(data, offset) {
None
} else {
Some(Self {
data,
offset,
key: CacheKey::new(),
})
}
}
}
impl<'a> RawFont<'a> for FontRef<'a> {
fn data(&self) -> &'a [u8] {
self.data
}
fn offset(&self) -> u32 {
self.offset
}
}
/// Iterator over a collection of fonts.
pub struct Fonts<'a> {
data: FontDataRef<'a>,
pos: usize,
}
impl<'a> Iterator for Fonts<'a> {
type Item = FontRef<'a>;
fn size_hint(&self) -> (usize, Option<usize>) {
let remaining = self.data.len - self.pos;
(remaining, Some(remaining))
}
fn nth(&mut self, n: usize) -> Option<Self::Item> {
let pos = self.pos.checked_add(n)?;
self.pos = pos.checked_add(1)?;
self.data.get(pos)
}
fn next(&mut self) -> Option<Self::Item> {
if self.pos >= self.data.len {
None
} else {
let pos = self.pos;
self.pos += 1;
self.data.get(pos)
}
}
}
impl<'a> ExactSizeIterator for Fonts<'a> {
fn len(&self) -> usize {
self.data.len - self.pos
}
}
impl<'a> IntoIterator for FontDataRef<'a> {
type IntoIter = Fonts<'a>;
type Item = FontRef<'a>;
fn into_iter(self) -> Self::IntoIter {
self.fonts()
}
}
/// Source that can provide table data by tag.
pub trait TableProvider {
/// Returns the table for the specified tag.
fn table_by_tag(&self, tag: Tag) -> Option<&[u8]>;
}
impl<'a> TableProvider for FontRef<'a> {
fn table_by_tag(&self, tag: Tag) -> Option<&[u8]> {
self.table_data(tag)
}
}
impl<'a> TableProvider for &'a FontRef<'a> {
fn table_by_tag(&self, tag: Tag) -> Option<&[u8]> {
self.table_data(tag)
}
}