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};
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 LookupFlag {
32    /// This bit relates only to the correct processing of GPOS type 3 (cursive attachment) lookups
33    ///
34    /// When this bit is set, the last glyph in a given sequence to which the cursive
35    /// attachment lookup is applied, will be positioned on the baseline.
36    pub const RIGHT_TO_LEFT: Self = LookupFlag(0x0001);
37    /// If set, skips over base glyphs
38    pub const IGNORE_BASE_GLYPHS: Self = LookupFlag(0x002);
39    /// If set, skips over ligatures
40    pub const IGNORE_LIGATURES: Self = LookupFlag(0x004);
41    /// If set, skips over all combining marks
42    pub const IGNORE_MARKS: Self = LookupFlag(0x008);
43    /// If set, indicates that the lookup table structure is followed by a MarkFilteringSet field.
44    ///
45    /// The layout engine skips over all mark glyphs not in the mark filtering set indicated.
46    pub const USE_MARK_FILTERING_SET: Self = LookupFlag(0x010);
47
48    // union of all flags, above
49    const FLAG_MASK: Self = LookupFlag(0x1F);
50
51    /// Return new, empty flags
52    pub fn empty() -> Self {
53        Self(0)
54    }
55
56    /// Construct a LookupFlag from a raw value, discarding invalid bits
57    pub fn from_bits_truncate(bits: u16) -> Self {
58        const VALID_BITS: u16 = !0x00E0;
59        Self(bits & VALID_BITS)
60    }
61
62    /// Raw transmutation to u16.
63    pub fn to_bits(self) -> u16 {
64        self.0
65    }
66
67    /// Returns `true` if all of the flags in `other` are contained within `self`.
68    #[inline]
69    pub const fn contains(&self, other: Self) -> bool {
70        // only count flag bits
71        let other = other.0 & Self::FLAG_MASK.0;
72        (self.0 & other) == other
73    }
74
75    /// If not zero, skips over all marks of attachment type different from specified.
76    pub fn mark_attachment_class(self) -> Option<u16> {
77        let val = self.0 & 0xff00;
78        if val == 0 {
79            None
80        } else {
81            Some(val >> 8)
82        }
83    }
84
85    /// If not zero, skips over all marks of attachment type different from specified.
86    pub fn set_mark_attachment_class(&mut self, val: u16) {
87        let val = (val & 0xff) << 8;
88        self.0 = (self.0 & 0xff) | val;
89    }
90}
91
92impl types::Scalar for LookupFlag {
93    type Raw = <u16 as types::Scalar>::Raw;
94    fn to_raw(self) -> Self::Raw {
95        self.0.to_raw()
96    }
97    fn from_raw(raw: Self::Raw) -> Self {
98        let t = <u16>::from_raw(raw);
99        Self(t)
100    }
101}
read_fonts/tables/layout/lookup_flag.rs

read_fonts/tables/layout/
lookup_flag.rs
