read_fonts/tables/layout/
lookup_flag.rs

1//! The lookup flag type.
2//!
3//! This is kind-of-but-not-quite-exactly a bit enumeration, and so we implement
4//! it manually.
5
6use core::ops::{BitOr, BitOrAssign, Sub};
7
8/// The [LookupFlag](https://learn.microsoft.com/en-us/typography/opentype/spec/chapter2#lookupFlag) bit enumeration.
9#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
10#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
11pub struct LookupFlag(u16);
12
13//NOTE: this impl has the potential to make garbage if used on two lookupflag
14//instances which have different mark attachment masks set, but as that field
15//is not really used in compilation, which is where this impl will be helpful,
16//the risk that this is the source of an actual bug seems very low,
17impl BitOr for LookupFlag {
18    type Output = Self;
19
20    fn bitor(self, rhs: Self) -> Self::Output {
21        Self(self.0 | rhs.0)
22    }
23}
24
25impl BitOrAssign for LookupFlag {
26    fn bitor_assign(&mut self, rhs: Self) {
27        self.0 |= rhs.0
28    }
29}
30
31impl Sub for LookupFlag {
32    type Output = Self;
33    /// Returns the difference between the flags in `self` and `other`.
34    #[inline]
35    fn sub(self, rhs: Self) -> Self {
36        Self(self.0 & !rhs.0)
37    }
38}
39
40impl LookupFlag {
41    /// This bit relates only to the correct processing of GPOS type 3 (cursive attachment) lookups
42    ///
43    /// When this bit is set, the last glyph in a given sequence to which the cursive
44    /// attachment lookup is applied, will be positioned on the baseline.
45    pub const RIGHT_TO_LEFT: Self = LookupFlag(0x0001);
46    /// If set, skips over base glyphs
47    pub const IGNORE_BASE_GLYPHS: Self = LookupFlag(0x002);
48    /// If set, skips over ligatures
49    pub const IGNORE_LIGATURES: Self = LookupFlag(0x004);
50    /// If set, skips over all combining marks
51    pub const IGNORE_MARKS: Self = LookupFlag(0x008);
52    /// If set, indicates that the lookup table structure is followed by a MarkFilteringSet field.
53    ///
54    /// The layout engine skips over all mark glyphs not in the mark filtering set indicated.
55    pub const USE_MARK_FILTERING_SET: Self = LookupFlag(0x010);
56
57    // union of all flags, above
58    const FLAG_MASK: Self = LookupFlag(0x1F);
59
60    /// Return new, empty flags
61    pub fn empty() -> Self {
62        Self(0)
63    }
64
65    /// Construct a LookupFlag from a raw value, discarding invalid bits
66    pub fn from_bits_truncate(bits: u16) -> Self {
67        const VALID_BITS: u16 = !0x00E0;
68        Self(bits & VALID_BITS)
69    }
70
71    /// Raw transmutation to u16.
72    pub fn to_bits(self) -> u16 {
73        self.0
74    }
75
76    /// Returns `true` if all of the flags in `other` are contained within `self`.
77    #[inline]
78    pub const fn contains(&self, other: Self) -> bool {
79        // only count flag bits
80        let other = other.0 & Self::FLAG_MASK.0;
81        (self.0 & other) == other
82    }
83
84    /// If not zero, skips over all marks of attachment type different from specified.
85    pub fn mark_attachment_class(self) -> Option<u16> {
86        let val = self.0 & 0xff00;
87        if val == 0 {
88            None
89        } else {
90            Some(val >> 8)
91        }
92    }
93
94    /// If not zero, skips over all marks of attachment type different from specified.
95    pub fn set_mark_attachment_class(&mut self, val: u16) {
96        let val = (val & 0xff) << 8;
97        self.0 = (self.0 & 0xff) | val;
98    }
99}
100
101impl types::Scalar for LookupFlag {
102    type Raw = <u16 as types::Scalar>::Raw;
103    fn to_raw(self) -> Self::Raw {
104        self.0.to_raw()
105    }
106    fn from_raw(raw: Self::Raw) -> Self {
107        let t = <u16>::from_raw(raw);
108        Self(t)
109    }
110}
read_fonts/tables/layout/lookup_flag.rs

read_fonts/tables/layout/
lookup_flag.rs
