usvg/parser/
mask.rs

1// Copyright 2018 the Resvg Authors
2// SPDX-License-Identifier: Apache-2.0 OR MIT
3
4use std::sync::Arc;
5
6use svgtypes::{Length, LengthUnit as Unit};
7
8use super::svgtree::{AId, EId, SvgNode};
9use super::{converter, OptionLog};
10use crate::{Group, Mask, MaskType, Node, NonEmptyString, NonZeroRect, Transform, Units};
11
12pub(crate) fn convert(
13    node: SvgNode,
14    state: &converter::State,
15    object_bbox: Option<NonZeroRect>,
16    cache: &mut converter::Cache,
17) -> Option<Arc<Mask>> {
18    // A `mask` attribute must reference a `mask` element.
19    if node.tag_name() != Some(EId::Mask) {
20        return None;
21    }
22
23    let units = node
24        .attribute(AId::MaskUnits)
25        .unwrap_or(Units::ObjectBoundingBox);
26
27    let content_units = node
28        .attribute(AId::MaskContentUnits)
29        .unwrap_or(Units::UserSpaceOnUse);
30
31    // Check if this element was already converted.
32    //
33    // Only `userSpaceOnUse` masks can be shared,
34    // because `objectBoundingBox` one will be converted into user one
35    // and will become node-specific.
36    let cacheable = units == Units::UserSpaceOnUse && content_units == Units::UserSpaceOnUse;
37    if cacheable {
38        if let Some(mask) = cache.masks.get(node.element_id()) {
39            return Some(mask.clone());
40        }
41    }
42
43    let rect = NonZeroRect::from_xywh(
44        node.convert_length(AId::X, units, state, Length::new(-10.0, Unit::Percent)),
45        node.convert_length(AId::Y, units, state, Length::new(-10.0, Unit::Percent)),
46        node.convert_length(AId::Width, units, state, Length::new(120.0, Unit::Percent)),
47        node.convert_length(AId::Height, units, state, Length::new(120.0, Unit::Percent)),
48    );
49    let mut rect =
50        rect.log_none(|| log::warn!("Mask '{}' has an invalid size. Skipped.", node.element_id()))?;
51
52    let mut mask_all = false;
53    if units == Units::ObjectBoundingBox {
54        if let Some(bbox) = object_bbox {
55            rect = rect.bbox_transform(bbox)
56        } else {
57            // When mask units are `objectBoundingBox` and bbox is zero-sized - the whole
58            // element should be masked.
59            // Technically an UB, but this is what Chrome and Firefox do.
60            mask_all = true;
61        }
62    }
63
64    let mut id = NonEmptyString::new(node.element_id().to_string())?;
65    // Generate ID only when we're parsing `objectBoundingBox` mask for the second time.
66    if !cacheable && cache.masks.contains_key(id.get()) {
67        id = cache.gen_mask_id();
68    }
69    let id_copy = id.get().to_string();
70
71    if mask_all {
72        let mask = Arc::new(Mask {
73            id,
74            rect,
75            kind: MaskType::Luminance,
76            mask: None,
77            root: Group::empty(),
78        });
79        cache.masks.insert(id_copy, mask.clone());
80        return Some(mask);
81    }
82
83    // Resolve linked mask.
84    let mut mask = None;
85    if let Some(link) = node.attribute::<SvgNode>(AId::Mask) {
86        mask = convert(link, state, object_bbox, cache);
87
88        // Linked `mask` must be valid.
89        if mask.is_none() {
90            return None;
91        }
92    }
93
94    let kind = if node.attribute(AId::MaskType) == Some("alpha") {
95        MaskType::Alpha
96    } else {
97        MaskType::Luminance
98    };
99
100    let mut mask = Mask {
101        id,
102        rect,
103        kind,
104        mask,
105        root: Group::empty(),
106    };
107
108    // To emulate content `objectBoundingBox` units we have to put
109    // mask children into a group with a transform.
110    let mut subroot = None;
111    if content_units == Units::ObjectBoundingBox {
112        let object_bbox = match object_bbox {
113            Some(v) => v,
114            None => {
115                log::warn!("Masking of zero-sized shapes is not allowed.");
116                return None;
117            }
118        };
119
120        let mut g = Group::empty();
121        g.transform = Transform::from_bbox(object_bbox);
122        // Make sure to set `abs_transform`, because it must propagate to all children.
123        g.abs_transform = g.transform;
124
125        subroot = Some(g);
126    }
127
128    {
129        // Prefer `subroot` to `mask.root`.
130        let real_root = subroot.as_mut().unwrap_or(&mut mask.root);
131        converter::convert_children(node, state, cache, real_root);
132
133        // A mask without children at this point is invalid.
134        // Only masks with zero bbox and `objectBoundingBox` can be empty.
135        if !real_root.has_children() {
136            return None;
137        }
138    }
139
140    if let Some(mut subroot) = subroot {
141        subroot.calculate_bounding_boxes();
142        mask.root.children.push(Node::Group(Box::new(subroot)));
143    }
144
145    mask.root.calculate_bounding_boxes();
146
147    let mask = Arc::new(mask);
148    cache.masks.insert(id_copy, mask.clone());
149    Some(mask)
150}
usvg/parser/mask.rs

usvg/parser/
mask.rs
