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use core::str::FromStr;
use crate::Script;
/// Defines the direction in which text is to be read.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum Direction {
/// Initial, unset direction.
Invalid,
/// Text is set horizontally from left to right.
LeftToRight,
/// Text is set horizontally from right to left.
RightToLeft,
/// Text is set vertically from top to bottom.
TopToBottom,
/// Text is set vertically from bottom to top.
BottomToTop,
}
impl Direction {
#[inline]
pub(crate) fn is_horizontal(self) -> bool {
match self {
Direction::Invalid => false,
Direction::LeftToRight => true,
Direction::RightToLeft => true,
Direction::TopToBottom => false,
Direction::BottomToTop => false,
}
}
#[inline]
pub(crate) fn is_vertical(self) -> bool {
!self.is_horizontal()
}
#[inline]
pub(crate) fn is_forward(self) -> bool {
match self {
Direction::Invalid => false,
Direction::LeftToRight => true,
Direction::RightToLeft => false,
Direction::TopToBottom => true,
Direction::BottomToTop => false,
}
}
#[inline]
pub(crate) fn is_backward(self) -> bool {
!self.is_forward()
}
#[inline]
pub(crate) fn reverse(self) -> Self {
match self {
Direction::Invalid => Direction::Invalid,
Direction::LeftToRight => Direction::RightToLeft,
Direction::RightToLeft => Direction::LeftToRight,
Direction::TopToBottom => Direction::BottomToTop,
Direction::BottomToTop => Direction::TopToBottom,
}
}
pub(crate) fn from_script(script: Script) -> Option<Self> {
// https://docs.google.com/spreadsheets/d/1Y90M0Ie3MUJ6UVCRDOypOtijlMDLNNyyLk36T6iMu0o
match script {
// Unicode-1.1 additions
Script::ARABIC |
Script::HEBREW |
// Unicode-3.0 additions
Script::SYRIAC |
Script::THAANA |
// Unicode-4.0 additions
Script::CYPRIOT |
// Unicode-4.1 additions
Script::KHAROSHTHI |
// Unicode-5.0 additions
Script::PHOENICIAN |
Script::NKO |
// Unicode-5.1 additions
Script::LYDIAN |
// Unicode-5.2 additions
Script::AVESTAN |
Script::IMPERIAL_ARAMAIC |
Script::INSCRIPTIONAL_PAHLAVI |
Script::INSCRIPTIONAL_PARTHIAN |
Script::OLD_SOUTH_ARABIAN |
Script::OLD_TURKIC |
Script::SAMARITAN |
// Unicode-6.0 additions
Script::MANDAIC |
// Unicode-6.1 additions
Script::MEROITIC_CURSIVE |
Script::MEROITIC_HIEROGLYPHS |
// Unicode-7.0 additions
Script::MANICHAEAN |
Script::MENDE_KIKAKUI |
Script::NABATAEAN |
Script::OLD_NORTH_ARABIAN |
Script::PALMYRENE |
Script::PSALTER_PAHLAVI |
// Unicode-8.0 additions
Script::HATRAN |
// Unicode-9.0 additions
Script::ADLAM |
// Unicode-11.0 additions
Script::HANIFI_ROHINGYA |
Script::OLD_SOGDIAN |
Script::SOGDIAN |
// Unicode-12.0 additions
Script::ELYMAIC |
// Unicode-13.0 additions
Script::CHORASMIAN |
Script::YEZIDI |
// Unicode-14.0 additions
Script::OLD_UYGHUR |
// Unicode-16.0 additions
Script::GARAY |
// Unicode-17.0 additions
Script::SIDETIC => {
Some(Direction::RightToLeft)
}
// https://github.com/harfbuzz/harfbuzz/issues/1000
Script::OLD_HUNGARIAN |
Script::OLD_ITALIC |
Script::RUNIC |
Script::TIFINAGH => {
None
}
_ => Some(Direction::LeftToRight),
}
}
}
impl Default for Direction {
#[inline]
fn default() -> Self {
Direction::Invalid
}
}
impl FromStr for Direction {
type Err = &'static str;
fn from_str(s: &str) -> Result<Self, Self::Err> {
if s.is_empty() {
return Err("invalid direction");
}
// harfbuzz also matches only the first letter.
match s.as_bytes()[0].to_ascii_lowercase() {
b'l' => Ok(Direction::LeftToRight),
b'r' => Ok(Direction::RightToLeft),
b't' => Ok(Direction::TopToBottom),
b'b' => Ok(Direction::BottomToTop),
_ => Err("invalid direction"),
}
}
}