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Merged
softmarshmallow merged 1 commit into from
Aug 29, 2026
Merged

websem: close the SVG points attribute #116

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9 changes: 5 additions & 4 deletions crates/n0_cli/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -74,8 +74,9 @@ cargo run -p n0_cli --bin n0 -- \
remains a named refusal because the pinned
cascade has no corresponding longhand. Also admitted are `<line>`, `<polygon>`
and `<polyline>` (the `points` grammar through the same number scanner as
path data; an erroneous list refuses the whole element by name where
Chromium renders its valid pair prefix — a declared divergence), nested in
path data; a final unmatched x coordinate is dropped after all complete
pairs, while every lexical or numeric parse failure resolves to the empty
list), nested in
`<g>` (and `<a>`, the same container semantics) with the whole `transform`
grammar, under the outer `<svg>`.
On `<circle>` and `<ellipse>`, the `cx`/`cy` presentation attributes default
Expand Down Expand Up @@ -539,8 +540,8 @@ cargo run -p n0_cli --bin n0 -- \
The filter estate contains 26 chassis/blur cells, 60 shadow-graph, 28 native
drop-shadow, 27 color-matrix, 32 component-transfer, 38 blend, 37 morphology,
91 turbulence/displacement, 41 convolution-rung, and 71 diffuse-lighting
cells. The complete corpus contains 1,026 Chromium-baked cells plus 16 sampled
frames, with 189 named
cells. The complete corpus contains 1,035 Chromium-baked cells plus 16 sampled
frames, with 188 named
refusal rows. `feFlood`, `feComposite`,
`feMerge`, `feMergeNode`, `feDropShadow`, `feColorMatrix`,
`feComponentTransfer`, `feBlend`, `feMorphology`, `feConvolveMatrix`,
Expand Down
101 changes: 16 additions & 85 deletions crates/websem/src/svg.rs
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Expand Up @@ -362,20 +362,10 @@ pub enum CompileError {
/// Chromium silently falls back to the default `xMidYMid meet` for
/// these; the slice refuses by name instead of silently defaulting.
BadPreserveAspectRatio(String),
/// A `points` list outside the SVG2 §10.4 grammar. Chromium renders the
/// valid coordinate-pair prefix and drops the rest; this slice refuses
/// the whole element by name instead, so an odd trailing coordinate is
/// one named hole, never a silently different shape.
BadPoints {
element: String,
/// Byte offset where the value stopped being a valid points list.
offset: usize,
excerpt: String,
},
/// A producer-normalized path stream the resolved contract rejected.
/// Source `d` syntax errors are finalized at the last complete segment;
/// this variant therefore names a compiler arithmetic/contract failure,
/// not authored malformed path data.
/// Source `d` errors and authored point-list errors are finalized before
/// this boundary; this variant therefore names a compiler
/// arithmetic/contract failure, not malformed source data.
BadPathData {
element: String,
/// Reserved source offset; normalized-stream failures use zero.
Expand Down Expand Up @@ -904,14 +894,6 @@ impl std::fmt::Display for CompileError {
CompileError::BadPreserveAspectRatio(v) => {
write!(f, "preserveAspectRatio {v:?} is invalid")
}
CompileError::BadPoints {
element,
offset,
excerpt,
} => write!(
f,
"points on <{element}> is invalid at byte {offset} (near {excerpt:?})"
),
CompileError::BadPathData {
element,
offset,
Expand Down Expand Up @@ -2224,13 +2206,7 @@ fn measure_leaf_geometry(
let Some(value) = get_attr(el, "points") else {
return Ok(MeasuredGeometry::Empty);
};
let points = crate::svg_path::parse_points(&value).map_err(
|crate::svg_path::SourceSyntaxError::Syntax { offset }| CompileError::BadPoints {
element: el.local_name_string(),
offset,
excerpt: excerpt_at(&value, offset),
},
)?;
let points = crate::svg_path::parse_points(&value);
if points.is_empty() {
return Ok(MeasuredGeometry::Empty);
}
Expand Down Expand Up @@ -5874,18 +5850,7 @@ mod clip_path {
}
"polygon" | "polyline" => {
let points = get_attr(element, "points")
.map(|value| {
crate::svg_path::parse_points(&value).map_err(
|crate::svg_path::SourceSyntaxError::Syntax { offset }| {
CompileError::BadPoints {
element: tag.clone(),
offset,
excerpt: excerpt_at(&value, offset),
}
},
)
})
.transpose()?
.map(|value| crate::svg_path::parse_points(&value))
.unwrap_or_default();
let Some(((first_x, first_y), rest)) = points.split_first() else {
return Ok(Geometry::Rect(Rectangle::empty()));
Expand All @@ -5902,7 +5867,7 @@ mod clip_path {
commands.push(rframe::PathCommand::Close);
}
Geometry::Path(Arc::new(PathData::new(commands, fill_rule).map_err(
|error| CompileError::BadPoints {
|error| CompileError::BadPathData {
element: tag,
offset: 0,
excerpt: error.to_string(),
Expand Down Expand Up @@ -9452,18 +9417,9 @@ fn prepare_marker_projection(
})
}
"polygon" | "polyline" if projects => {
let points = match get_attr(el, "points") {
None => Vec::new(),
Some(value) => crate::svg_path::parse_points(&value).map_err(
|crate::svg_path::SourceSyntaxError::Syntax { offset }| {
CompileError::BadPoints {
element: tag.to_string(),
offset,
excerpt: excerpt_at(&value, offset),
}
},
)?,
};
let points = get_attr(el, "points")
.map(|value| crate::svg_path::parse_points(&value))
.unwrap_or_default();
Ok(MarkerProjection {
parsed_path: None,
positions: crate::svg_path::points_marker_positions(&points, tag == "polygon"),
Expand Down Expand Up @@ -10177,10 +10133,9 @@ enum PointsClosure {
/// geometry kind of its own, exactly as `<line>` lowers.
///
/// The `points` list maps to `MoveTo` + `LineTo`* (+ `Close` for a
/// polygon). Chromium renders the valid coordinate-pair prefix of an
/// erroneous list; this slice refuses the whole element by name instead
/// (see [`CompileError::BadPoints`]). A missing or empty list is valid and
/// renders nothing, like an empty `d`.
/// polygon). A final unmatched x coordinate is dropped after retaining every
/// complete pair; any lexical or numeric parse error clears the list. A
/// missing or empty list is valid and renders nothing, like an empty `d`.
fn compile_points_shape(
el: HtmlElement<'_>,
viewport: AffineTransform,
Expand Down Expand Up @@ -10213,16 +10168,9 @@ fn compile_points_shape(
if patrol.opacity == 0.0 {
return Ok(None);
}
let points = match get_attr(el, "points") {
None => Vec::new(),
Some(value) => crate::svg_path::parse_points(&value).map_err(
|crate::svg_path::SourceSyntaxError::Syntax { offset }| CompileError::BadPoints {
element: element.to_string(),
offset,
excerpt: excerpt_at(&value, offset),
},
)?,
};
let points = get_attr(el, "points")
.map(|value| crate::svg_path::parse_points(&value))
.unwrap_or_default();
let Some(((first_x, first_y), rest)) = points.split_first() else {
return Ok(None);
};
Expand Down Expand Up @@ -10256,7 +10204,7 @@ fn compile_points_shape(
let path = PathData::new(commands, resolve_fill_rule(el)?).map_err(|error| {
// The producer normalizes into the contract's canonical form, so a
// rejection here is this compiler's bug, not the document's.
CompileError::BadPoints {
CompileError::BadPathData {
element: element.to_string(),
offset: 0,
excerpt: error.to_string(),
Expand Down Expand Up @@ -10285,23 +10233,6 @@ fn compile_points_shape(
.map(Some)
}

/// The authored text at an error offset, clipped to a readable excerpt on a
/// character boundary.
fn excerpt_at(value: &str, offset: usize) -> String {
/// Long enough to show the offending token, short enough that a
/// kilobyte-long `d` does not reach a terminal.
const WIDTH: usize = 24;
let start = (0..=offset.min(value.len()))
.rev()
.find(|index| value.is_char_boundary(*index))
.unwrap_or(0);
let end = (start..=(start + WIDTH).min(value.len()))
.rev()
.find(|index| value.is_char_boundary(*index))
.unwrap_or(value.len());
value[start..end].to_string()
}

/// The cascaded `fill-rule` — which regions of a self-overlapping path the
/// fill covers. Read as a typed computed value like `fill`, so the SVG2
/// precedence (presentation attribute below author rules), inheritance
Expand Down
35 changes: 24 additions & 11 deletions crates/websem/src/svg_path.rs
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Expand Up @@ -121,8 +121,8 @@ pub(crate) enum MarkerPathElement {

/// Why one SVG numeric grammar stopped parsing.
///
/// Path data itself consumes its valid prefix when this occurs. `points`
/// retains the error because its valid-pair-prefix rule is a separate rung.
/// Path data itself consumes its valid prefix when this occurs. Point lists
/// use the same scanner but finalize their own list-level error semantics.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum SourceSyntaxError {
/// The source value stopped being valid at this byte offset.
Expand All @@ -145,28 +145,41 @@ pub(crate) fn parse_path(d: &str) -> ParsedPath {
Parser::new(d).parse_path_prefix()
}

/// Parse one `points` list (SVG2 §10.4) into coordinate pairs, through the
/// same number scanner as path data so the two grammars cannot drift.
/// Parse one `points` list (SVG2 §10.4) into Chromium's used coordinate pairs,
/// through the same number scanner as path data so the two grammars cannot
/// drift.
///
/// The separator rules are Blink's, measured against Chromium 149: a
/// trailing separator after the last complete pair is accepted (unlike the
/// `viewBox` grammar), a leading or doubled comma is an error, a trailing
/// dot needs a digit, and a sign starts a new number (`32-56` is two).
/// Chromium renders the valid *pair prefix* of an erroneous list; this
/// slice refuses the whole element by name instead — the same declared
/// divergence as path data, so an odd trailing coordinate is one named
/// hole, never a silently different shape.
/// A final unmatched x coordinate, with or without one trailing comma, is the
/// one recoverable error: it is dropped and all complete pairs remain. Every
/// lexical or numeric failure clears the whole list, including one after an
/// unmatched x; no malformed-list prefix survives.
///
/// An empty (or whitespace-only) value is valid and resolves to no points,
/// which renders nothing.
pub(crate) fn parse_points(value: &str) -> Result<Vec<(f32, f32)>, SourceSyntaxError> {
pub(crate) fn parse_points(value: &str) -> Vec<(f32, f32)> {
let mut parser = Parser::new(value);
parser.skip_wsp();
let mut points = Vec::new();
while parser.at < parser.bytes.len() {
points.push(parser.coordinate_pair()?);
let Ok(x) = parser.number() else {
return Vec::new();
};
// Blink emits only complete pairs. Reaching the end after x is the
// SVGPointList odd-count exception, including when x consumed one
// trailing comma.
if parser.at == parser.bytes.len() {
return points;
}
let Ok(y) = parser.number() else {
return Vec::new();
};
points.push((x, y));
}
Ok(points)
points
}

/// The five ASCII characters Blink's SVG parsers treat as whitespace
Expand Down
9 changes: 5 additions & 4 deletions crates/websem/tests/context_paint_contract.rs
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Expand Up @@ -428,11 +428,12 @@ fn unknown_geometry_never_becomes_a_partial_context_box() {

#[test]
fn an_unindexed_nested_use_is_unknown_not_empty() {
// The odd `points` coordinate is a registered whole-element departure.
// Its measurement error deliberately prevents the outer group's prepass
// entry; the nested use must not reinterpret that absence as an empty box.
// The unit-bearing `x` is a registered whole-element `BadNumber`
// over-refusal. Its measurement error deliberately prevents the outer
// group's prepass entry; the nested use must not reinterpret that absence
// as an empty box.
let source = document(
r##"<defs><linearGradient id="g"><stop offset="0" stop-color="red"/><stop offset="1" stop-color="blue"/></linearGradient><rect id="leaf" x="8" y="8" width="24" height="24" fill="context-fill"/><g id="outer"><polygon points="8,8 20"/><use href="#leaf" fill="url(#g)"/></g></defs><use href="#outer"/>"##,
r##"<defs><linearGradient id="g"><stop offset="0" stop-color="red"/><stop offset="1" stop-color="blue"/></linearGradient><rect id="leaf" x="8" y="8" width="24" height="24" fill="context-fill"/><g id="outer"><rect x="8px" y="8" width="1" height="1"/><use href="#leaf" fill="url(#g)"/></g></defs><use href="#outer"/>"##,
);
let best = SvgFrameSource::from_standalone_svg_best_effort(source.as_str(), viewport())
.expect("best effort names both holes");
Expand Down
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