write_fonts/tables/glyf/
composite.rs

1//! Composite glyphs (containing other glyphs as components)
2
3use crate::{
4    from_obj::{FromObjRef, FromTableRef, ToOwnedTable},
5    FontWrite,
6};
7
8use read_fonts::{tables::glyf::CompositeGlyphFlags, types::GlyphId16, FontRead};
9
10use super::Bbox;
11
12pub use read_fonts::tables::glyf::{Anchor, Transform};
13
14/// A glyph consisting of multiple component sub-glyphs
15#[derive(Clone, Debug, PartialEq, Eq)]
16pub struct CompositeGlyph {
17    pub bbox: Bbox,
18    components: Vec<Component>,
19    _instructions: Vec<u8>,
20}
21
22/// A single component glyph (part of a [`CompositeGlyph`]).
23#[derive(Clone, Debug, PartialEq, Eq)]
24pub struct Component {
25    pub glyph: GlyphId16,
26    pub anchor: Anchor,
27    pub flags: ComponentFlags,
28    pub transform: Transform,
29}
30
31/// Options that can be manually set for a given component.
32///
33/// This provides an easier interface for setting those flags that are not
34/// calculated based on other properties of the glyph. For more information
35/// on these flags, see [Component Glyph Flags](flags-spec) in the spec.
36///
37/// These eventually are combined with calculated flags into the
38/// [`CompositeGlyphFlags`] bitset.
39///
40/// [flags-spec]: https://learn.microsoft.com/en-us/typography/opentype/spec/glyf#compositeGlyphFlags
41#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
42pub struct ComponentFlags {
43    /// Round xy values to the nearest grid line
44    pub round_xy_to_grid: bool,
45    /// Use the advance/lsb/rsb values of this component for the whole
46    /// composite glyph
47    pub use_my_metrics: bool,
48    /// The composite should have this component's offset scaled
49    pub scaled_component_offset: bool,
50    /// The composite should *not* have this component's offset scaled
51    pub unscaled_component_offset: bool,
52    /// If set, the components of the composite glyph overlap.
53    pub overlap_compound: bool,
54}
55
56impl FromObjRef<read_fonts::tables::glyf::CompositeGlyph<'_>> for CompositeGlyph {
57    fn from_obj_ref(
58        from: &read_fonts::tables::glyf::CompositeGlyph,
59        _data: read_fonts::FontData,
60    ) -> Self {
61        let bbox = Bbox {
62            x_min: from.x_min(),
63            y_min: from.y_min(),
64            x_max: from.x_max(),
65            y_max: from.y_max(),
66        };
67        let components = from
68            .components()
69            .map(|c| Component {
70                glyph: c.glyph,
71                anchor: c.anchor,
72                flags: c.flags.into(),
73                transform: c.transform,
74            })
75            .collect();
76        Self {
77            bbox,
78            components,
79            _instructions: from
80                .instructions()
81                .map(|v| v.to_owned())
82                .unwrap_or_default(),
83        }
84    }
85}
86
87impl FromTableRef<read_fonts::tables::glyf::CompositeGlyph<'_>> for CompositeGlyph {}
88
89impl<'a> FontRead<'a> for CompositeGlyph {
90    fn read(data: read_fonts::FontData<'a>) -> Result<Self, read_fonts::ReadError> {
91        read_fonts::tables::glyf::CompositeGlyph::read(data).map(|g| g.to_owned_table())
92    }
93}
94
95impl Component {
96    /// Create a new component.
97    pub fn new(
98        glyph: GlyphId16,
99        anchor: Anchor,
100        transform: Transform,
101        flags: impl Into<ComponentFlags>,
102    ) -> Self {
103        Component {
104            glyph,
105            anchor,
106            flags: flags.into(),
107            transform,
108        }
109    }
110    /// Compute the flags for this glyph, excepting `MORE_COMPONENTS` and
111    /// `WE_HAVE_INSTRUCTIONS`, which must be set manually
112    fn compute_flag(&self) -> CompositeGlyphFlags {
113        self.anchor.compute_flags() | self.transform.compute_flags() | self.flags.into()
114    }
115
116    /// like `FontWrite` but lets us pass in the flags that must be determined
117    /// externally (WE_HAVE_INSTRUCTIONS and MORE_COMPONENTS)
118    fn write_into(&self, writer: &mut crate::TableWriter, extra_flags: CompositeGlyphFlags) {
119        let flags = self.compute_flag() | extra_flags;
120        flags.bits().write_into(writer);
121        self.glyph.write_into(writer);
122        self.anchor.write_into(writer);
123        self.transform.write_into(writer);
124    }
125}
126
127/// An error that occurs if a `CompositeGlyph` is constructed with no components.
128#[derive(Clone, Copy, Debug)]
129#[non_exhaustive]
130pub struct NoComponents;
131
132impl std::fmt::Display for NoComponents {
133    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
134        write!(f, "A composite glyph must contain at least one component")
135    }
136}
137
138impl std::error::Error for NoComponents {}
139
140impl CompositeGlyph {
141    /// Create a new composite glyph, with the provided component.
142    ///
143    /// The 'bbox' argument is the bounding box of the glyph after the transform
144    /// has been applied.
145    ///
146    /// Additional components can be added with [`add_component`][Self::add_component]
147    pub fn new(component: Component, bbox: impl Into<Bbox>) -> Self {
148        Self {
149            bbox: bbox.into(),
150            components: vec![component],
151            _instructions: Default::default(),
152        }
153    }
154
155    /// Add a new component to this glyph
156    ///
157    /// The 'bbox' argument is the bounding box of the glyph after the transform
158    /// has been applied.
159    pub fn add_component(&mut self, component: Component, bbox: impl Into<Bbox>) {
160        self.components.push(component);
161        self.bbox = self.bbox.union(bbox.into());
162    }
163
164    /// Construct a `CompositeGlyph` from an iterator of `Component` and `Bbox`es.
165    ///
166    /// This returns an error if the iterator is empty; a CompositeGlyph must always
167    /// contain at least one component.
168    pub fn try_from_iter(
169        source: impl IntoIterator<Item = (Component, Bbox)>,
170    ) -> Result<Self, NoComponents> {
171        let mut components = Vec::new();
172        let mut union_box: Option<Bbox> = None;
173
174        for (component, bbox) in source {
175            components.push(component);
176            union_box.get_or_insert(bbox).union(bbox);
177        }
178
179        if components.is_empty() {
180            Err(NoComponents)
181        } else {
182            Ok(CompositeGlyph {
183                bbox: union_box.unwrap(),
184                components,
185                _instructions: Default::default(),
186            })
187        }
188    }
189
190    pub fn components(&self) -> &[Component] {
191        &self.components
192    }
193}
194
195impl FontWrite for CompositeGlyph {
196    fn write_into(&self, writer: &mut crate::TableWriter) {
197        const N_CONTOURS: i16 = -1;
198        N_CONTOURS.write_into(writer);
199        self.bbox.write_into(writer);
200        let (last, rest) = self
201            .components
202            .split_last()
203            .expect("empty composites checked in validation");
204        for comp in rest {
205            comp.write_into(writer, CompositeGlyphFlags::MORE_COMPONENTS);
206        }
207        let last_flags = if self._instructions.is_empty() {
208            CompositeGlyphFlags::empty()
209        } else {
210            CompositeGlyphFlags::WE_HAVE_INSTRUCTIONS
211        };
212        last.write_into(writer, last_flags);
213
214        if !self._instructions.is_empty() {
215            (self._instructions.len() as u16).write_into(writer);
216            self._instructions.write_into(writer);
217        }
218        writer.pad_to_2byte_aligned();
219    }
220}
221
222impl crate::validate::Validate for CompositeGlyph {
223    fn validate_impl(&self, ctx: &mut crate::codegen_prelude::ValidationCtx) {
224        if self.components.is_empty() {
225            ctx.report("composite glyph must have components");
226        }
227        if self._instructions.len() > u16::MAX as usize {
228            ctx.report("instructions len overflows");
229        }
230    }
231}
232
233impl FontWrite for Anchor {
234    fn write_into(&self, writer: &mut crate::TableWriter) {
235        let two_bytes = self
236            .compute_flags()
237            .contains(CompositeGlyphFlags::ARG_1_AND_2_ARE_WORDS);
238        match self {
239            Anchor::Offset { x, y } if !two_bytes => [*x as i8, *y as i8].write_into(writer),
240            Anchor::Offset { x, y } => [*x, *y].write_into(writer),
241            Anchor::Point { base, component } if !two_bytes => {
242                [*base as u8, *component as u8].write_into(writer)
243            }
244            Anchor::Point { base, component } => [*base, *component].write_into(writer),
245        }
246    }
247}
248
249impl FontWrite for Transform {
250    fn write_into(&self, writer: &mut crate::TableWriter) {
251        let flags = self.compute_flags();
252        if flags.contains(CompositeGlyphFlags::WE_HAVE_A_TWO_BY_TWO) {
253            [self.xx, self.yx, self.xy, self.yy].write_into(writer);
254        } else if flags.contains(CompositeGlyphFlags::WE_HAVE_AN_X_AND_Y_SCALE) {
255            [self.xx, self.yy].write_into(writer);
256        } else if flags.contains(CompositeGlyphFlags::WE_HAVE_A_SCALE) {
257            self.xx.write_into(writer)
258        }
259    }
260}
261
262impl From<CompositeGlyphFlags> for ComponentFlags {
263    fn from(src: CompositeGlyphFlags) -> ComponentFlags {
264        ComponentFlags {
265            round_xy_to_grid: src.contains(CompositeGlyphFlags::ROUND_XY_TO_GRID),
266            use_my_metrics: src.contains(CompositeGlyphFlags::USE_MY_METRICS),
267            scaled_component_offset: src.contains(CompositeGlyphFlags::SCALED_COMPONENT_OFFSET),
268            unscaled_component_offset: src.contains(CompositeGlyphFlags::UNSCALED_COMPONENT_OFFSET),
269            overlap_compound: src.contains(CompositeGlyphFlags::OVERLAP_COMPOUND),
270        }
271    }
272}
273
274impl From<ComponentFlags> for CompositeGlyphFlags {
275    fn from(value: ComponentFlags) -> Self {
276        (if value.round_xy_to_grid {
277            CompositeGlyphFlags::ROUND_XY_TO_GRID
278        } else {
279            Default::default()
280        }) | if value.use_my_metrics {
281            CompositeGlyphFlags::USE_MY_METRICS
282        } else {
283            Default::default()
284        } | if value.scaled_component_offset {
285            CompositeGlyphFlags::SCALED_COMPONENT_OFFSET
286        } else {
287            Default::default()
288        } | if value.unscaled_component_offset {
289            CompositeGlyphFlags::UNSCALED_COMPONENT_OFFSET
290        } else {
291            Default::default()
292        } | if value.overlap_compound {
293            CompositeGlyphFlags::OVERLAP_COMPOUND
294        } else {
295            Default::default()
296        }
297    }
298}
299
300#[cfg(test)]
301mod tests {
302
303    use read_fonts::{
304        tables::glyf as read_glyf, types::GlyphId, FontData, FontRead, FontRef, TableProvider,
305    };
306
307    use super::*;
308
309    #[test]
310    fn roundtrip_composite() {
311        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
312        let loca = font.loca(None).unwrap();
313        let glyf = font.glyf().unwrap();
314        let read_glyf::Glyph::Composite(orig) =
315            loca.get_glyf(GlyphId::new(2), &glyf).unwrap().unwrap()
316        else {
317            panic!("not a composite glyph")
318        };
319
320        let bbox = Bbox {
321            x_min: orig.x_min(),
322            y_min: orig.y_min(),
323            x_max: orig.x_max(),
324            y_max: orig.y_max(),
325        };
326        let mut iter = orig
327            .components()
328            .map(|comp| Component::new(comp.glyph, comp.anchor, comp.transform, comp.flags));
329        let mut composite = CompositeGlyph::new(iter.next().unwrap(), bbox);
330        composite.add_component(iter.next().unwrap(), bbox);
331        composite._instructions = orig.instructions().unwrap_or_default().to_vec();
332        assert!(iter.next().is_none());
333        let bytes = crate::dump_table(&composite).unwrap();
334        let ours = read_fonts::tables::glyf::CompositeGlyph::read(FontData::new(&bytes)).unwrap();
335
336        let our_comps = ours.components().collect::<Vec<_>>();
337        let orig_comps = orig.components().collect::<Vec<_>>();
338        assert_eq!(our_comps.len(), orig_comps.len());
339        assert_eq!(our_comps.len(), 2);
340        assert_eq!(&our_comps[0], &orig_comps[0]);
341        assert_eq!(&our_comps[1], &orig_comps[1]);
342        assert_eq!(ours.instructions(), orig.instructions());
343        assert_eq!(orig.offset_data().len(), bytes.len());
344
345        assert_eq!(orig.offset_data().as_ref(), bytes);
346    }
347}
write_fonts/tables/glyf/composite.rs

write_fonts/tables/glyf/
composite.rs
