/src/librsvg/rsvg/src/structure.rs

Source
//! Structural elements in SVG: the `g`, `switch`, `svg`, `use`, `symbol`, `clip_path`, `mask`, `link` elements.

use markup5ever::{expanded_name, local_name, ns};

use crate::aspect_ratio::*;
use crate::bbox::BoundingBox;
use crate::coord_units;
use crate::coord_units::CoordUnits;
use crate::document::{AcquiredNodes, NodeId};
use crate::drawing_ctx::{DrawingCtx, SvgNesting, Viewport};
use crate::element::{DrawResult, ElementData, ElementTrait, set_attribute};
use crate::error::*;
use crate::href::{is_href, set_href};
use crate::layout::{self, Layer, LayerKind, LayoutViewport, StackingContext};
use crate::length::*;
use crate::node::{CascadedValues, Node, NodeBorrow, NodeDraw};
use crate::parsers::{Parse, ParseValue};
use crate::properties::ComputedValues;
use crate::rect::Rect;
use crate::session::Session;
use crate::viewbox::*;
use crate::xml::Attributes;

#[derive(Default)]
pub struct Group();

impl ElementTrait for Group {
    fn draw(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
        _clipping: bool,
    ) -> DrawResult {
        let values = cascaded.get();

        let elt = node.borrow_element();
        let stacking_ctx = Box::new(StackingContext::new(
            draw_ctx,
            acquired_nodes,
            &elt,
            values.transform(),
            None,
            values,
            viewport,
        ));

        draw_ctx.with_discrete_layer(
            &stacking_ctx,
            acquired_nodes,
            viewport,
            None,
            false,
            &mut |an, dc, new_viewport| node.draw_children(an, cascaded, new_viewport, dc),
        )
    }

    fn layout(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
    ) -> Result<Option<Layer>, Box<InternalRenderingError>> {
        let mut child_layers = Vec::new();

        for child in node.children().filter(|c| c.is_element()) {
            let elt = child.borrow_element();

            let layer = elt.layout(
                &child,
                acquired_nodes,
                &CascadedValues::clone_with_node(cascaded, &child),
                viewport,
                draw_ctx,
            )?;

            if let Some(layer) = layer {
                child_layers.push(layer);
            }
        }

        self.layout_with_children(
            draw_ctx,
            node,
            acquired_nodes,
            cascaded,
            child_layers,
            viewport,
        )
    }
}

fn extents_of_transformed_children(layers: &[Layer]) -> Option<Rect> {
    let mut result_bbox = BoundingBox::new();

    for layer in layers {
        if let Some(extents) = layer.kind.local_extents() {
            let bbox = BoundingBox::new()
                .with_transform(layer.stacking_ctx.transform)
                .with_rect(extents);
            result_bbox.insert(&bbox);
        }
    }

    result_bbox.rect
}

impl Group {
    fn layout_with_children(
        &self,
        draw_ctx: &DrawingCtx,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        child_layers: Vec<Layer>,
        viewport: &Viewport,
    ) -> Result<Option<Layer>, Box<InternalRenderingError>> {
        let values = cascaded.get();

        let extents = extents_of_transformed_children(&child_layers);

        let group = Box::new(layout::Group {
            children: child_layers,
            establish_viewport: None,
            extents,
        });

        let elt = node.borrow_element();
        let stacking_ctx = StackingContext::new(
            draw_ctx,
            acquired_nodes,
            &elt,
            values.transform(),
            None,
            values,
            viewport,
        );

        Ok(Some(Layer {
            kind: LayerKind::Group(group),
            stacking_ctx,
        }))
    }
}

/// A no-op node that does not render anything
///
/// Sometimes we just need a node that can contain children, but doesn't
/// render itself or its children.  This is just that kind of node.
#[derive(Default)]
pub struct NonRendering;

impl ElementTrait for NonRendering {}

/// The `<switch>` element.
#[derive(Default)]
pub struct Switch();

impl ElementTrait for Switch {
    fn draw(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
        _clipping: bool,
    ) -> DrawResult {
        let values = cascaded.get();

        let switch_elt = node.borrow_element();
        let child_that_matches = node.children().filter(|c| c.is_element()).find(|c| {
            let elt = c.borrow_element();
            elt.get_cond(draw_ctx.user_language(), draw_ctx.session())
        });

        if let Some(child) = child_that_matches {
            let stacking_ctx = Box::new(StackingContext::new(
                draw_ctx,
                acquired_nodes,
                &switch_elt,
                values.transform(),
                None,
                values,
                viewport,
            ));

            draw_ctx.with_discrete_layer(
                &stacking_ctx,
                acquired_nodes,
                viewport,
                None,
                false,
                &mut |an, dc, new_viewport| {
                    child.draw(
                        an,
                        &CascadedValues::clone_with_node(cascaded, &child),
                        new_viewport,
                        dc,
                        false,
                    )
                },
            )
        } else {
            Ok(viewport.empty_bbox())
        }
    }
}

/// Intrinsic dimensions of an SVG document fragment: its `width/height` properties and  `viewBox` attribute.
///
/// Note that in SVG2, `width` and `height` are properties, not
/// attributes.  If either is omitted, it defaults to `auto`. which
/// computes to `100%`.
///
/// The `viewBox` attribute can also be omitted, hence an `Option`.
#[derive(Debug, Copy, Clone, PartialEq)]
pub struct IntrinsicDimensions {
    /// Computed value of the `width` property.
    pub width: ULength<Horizontal>,

    /// Computed value of the `height` property.
    pub height: ULength<Vertical>,

    /// Contents of the `viewBox` attribute.
    pub vbox: Option<ViewBox>,
}

/// The `<svg>` element.
///
/// Note that its x/y/width/height are properties in SVG2, so they are
/// defined as part of [the properties machinery](properties.rs).
#[derive(Default)]
pub struct Svg {
    preserve_aspect_ratio: AspectRatio,
    vbox: Option<ViewBox>,
}

impl Svg {
    pub fn get_intrinsic_dimensions(&self, values: &ComputedValues) -> IntrinsicDimensions {
        let w = match values.width().0 {
            LengthOrAuto::Auto => ULength::<Horizontal>::parse_str("100%").unwrap(),
            LengthOrAuto::Length(l) => l,
        };

        let h = match values.height().0 {
            LengthOrAuto::Auto => ULength::<Vertical>::parse_str("100%").unwrap(),
            LengthOrAuto::Length(l) => l,
        };

        IntrinsicDimensions {
            width: w,
            height: h,
            vbox: self.vbox,
        }
    }

    fn get_unnormalized_offset(
        &self,
        values: &ComputedValues,
    ) -> (Length<Horizontal>, Length<Vertical>) {
        // these defaults are per the spec
        let x = values.x().0;
        let y = values.y().0;

        (x, y)
    }

    fn get_unnormalized_size(
        &self,
        values: &ComputedValues,
    ) -> (ULength<Horizontal>, ULength<Vertical>) {
        // these defaults are per the spec
        let w = match values.width().0 {
            LengthOrAuto::Auto => ULength::<Horizontal>::parse_str("100%").unwrap(),
            LengthOrAuto::Length(l) => l,
        };
        let h = match values.height().0 {
            LengthOrAuto::Auto => ULength::<Vertical>::parse_str("100%").unwrap(),
            LengthOrAuto::Length(l) => l,
        };
        (w, h)
    }

    fn get_viewport(
        &self,
        params: &NormalizeParams,
        values: &ComputedValues,
        outermost: bool,
    ) -> Rect {
        // x & y attributes have no effect on outermost svg
        // http://www.w3.org/TR/SVG/struct.html#SVGElement
        let (nx, ny) = if outermost {
            (0.0, 0.0)
        } else {
            let (x, y) = self.get_unnormalized_offset(values);
            (x.to_user(params), y.to_user(params))
        };

        let (w, h) = self.get_unnormalized_size(values);
        let (nw, nh) = (w.to_user(params), h.to_user(params));

        Rect::new(nx, ny, nx + nw, ny + nh)
    }

    pub fn get_viewbox(&self) -> Option<ViewBox> {
        self.vbox
    }

    pub fn get_preserve_aspect_ratio(&self) -> AspectRatio {
        self.preserve_aspect_ratio
    }

    fn make_svg_viewport(
        &self,
        node: &Node,
        cascaded: &CascadedValues<'_>,
        current_viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
    ) -> LayoutViewport {
        let values = cascaded.get();

        let params = NormalizeParams::new(values, current_viewport);

        let has_parent = node.parent().is_some();

        // From https://www.w3.org/TR/SVG2/embedded.html#ImageElement:
        //
        // For `image` elements embedding an SVG image, the `preserveAspectRatio`
        // attribute on the root element in the referenced SVG image must be ignored,
        // and instead treated as if it had a value of `none`. (see
        // `preserveAspectRatio` for details).  This ensures that the
        // `preserveAspectRatio` attribute on the referencing `image` has its
        // intended effect, even if it is none.
        //
        let preserve_aspect_ratio = match (has_parent, draw_ctx.svg_nesting()) {
            // we are a toplevel, and referenced from <image> => preserveAspectRatio=none
            (false, SvgNesting::ReferencedFromImageElement) => AspectRatio::none(),

            // otherwise just use our specified preserveAspectRatio
            _ => self.preserve_aspect_ratio,
        };

        let svg_viewport = self.get_viewport(&params, values, !has_parent);

        let is_measuring_toplevel_svg = !has_parent && draw_ctx.is_measuring();

        let (geometry, vbox) = if is_measuring_toplevel_svg {
            // We are obtaining the toplevel SVG's geometry.  This means, don't care about the
            // DrawingCtx's viewport, just use the SVG's intrinsic dimensions and see how far
            // it wants to extend.
            (svg_viewport, self.vbox)
        } else {
            (
                // The client's viewport overrides the toplevel's x/y/w/h viewport
                if has_parent {
                    svg_viewport
                } else {
                    draw_ctx.toplevel_viewport()
                },
                // Use our viewBox if available, or try to derive one from
                // the intrinsic dimensions.
                self.vbox.or_else(|| {
                    Some(ViewBox::from(Rect::from_size(
                        svg_viewport.width(),
                        svg_viewport.height(),
                    )))
                }),
            )
        };

        LayoutViewport {
            geometry,
            vbox,
            preserve_aspect_ratio,
            overflow: values.overflow(),
        }
    }
}

impl ElementTrait for Svg {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            match attr.expanded() {
                expanded_name!("", "preserveAspectRatio") => {
                    set_attribute(&mut self.preserve_aspect_ratio, attr.parse(value), session)
                }
                expanded_name!("", "viewBox") => {
                    set_attribute(&mut self.vbox, attr.parse(value), session)
                }
                _ => (),
            }
        }
    }

    fn draw(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
        _clipping: bool,
    ) -> DrawResult {
        let values = cascaded.get();

        let elt = node.borrow_element();
        let stacking_ctx = Box::new(StackingContext::new(
            draw_ctx,
            acquired_nodes,
            &elt,
            values.transform(),
            None,
            values,
            viewport,
        ));

        let layout_viewport = self.make_svg_viewport(node, cascaded, viewport, draw_ctx);

        draw_ctx.with_discrete_layer(
            &stacking_ctx,
            acquired_nodes,
            viewport,
            Some(layout_viewport),
            false,
            &mut |an, dc, new_viewport| node.draw_children(an, cascaded, new_viewport, dc),
        )
    }

    fn layout(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
    ) -> Result<Option<Layer>, Box<InternalRenderingError>> {
        let mut child_layers = Vec::new();

        for child in node.children().filter(|c| c.is_element()) {
            let elt = child.borrow_element();

            let layer = elt.layout(
                &child,
                acquired_nodes,
                &CascadedValues::clone_with_node(cascaded, &child),
                viewport,
                draw_ctx,
            )?;

            if let Some(layer) = layer {
                child_layers.push(layer);
            }
        }

        let values = cascaded.get();
        let extents = extents_of_transformed_children(&child_layers);

        let layout_viewport = self.make_svg_viewport(node, cascaded, viewport, draw_ctx);

        let group = Box::new(layout::Group {
            children: child_layers,
            establish_viewport: Some(layout_viewport),
            extents,
        });

        let elt = node.borrow_element();
        let stacking_ctx = StackingContext::new(
            draw_ctx,
            acquired_nodes,
            &elt,
            values.transform(),
            None,
            values,
            viewport,
        );

        Ok(Some(Layer {
            kind: LayerKind::Group(group),
            stacking_ctx,
        }))
    }
}

/// The `<use>` element.
pub struct Use {
    link: Option<NodeId>,
    x: Length<Horizontal>,
    y: Length<Vertical>,
    width: ULength<Horizontal>,
    height: ULength<Vertical>,
}

impl Use {
    pub fn get_rect(&self, params: &NormalizeParams) -> Rect {
        let x = self.x.to_user(params);
        let y = self.y.to_user(params);
        let w = self.width.to_user(params);
        let h = self.height.to_user(params);

        Rect::new(x, y, x + w, y + h)
    }

    pub fn get_link(&self) -> Option<NodeId> {
        self.link.clone()
    }
}

impl Default for Use {
    fn default() -> Use {
        Use {
            link: None,
            x: Default::default(),
            y: Default::default(),
            width: ULength::<Horizontal>::parse_str("100%").unwrap(),
            height: ULength::<Vertical>::parse_str("100%").unwrap(),
        }
    }
}

impl ElementTrait for Use {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            match attr.expanded() {
                ref a if is_href(a) => {
                    let mut href = None;
                    set_attribute(
                        &mut href,
                        NodeId::parse(value).map(Some).attribute(attr.clone()),
                        session,
                    );
                    set_href(a, &mut self.link, href);
                }
                expanded_name!("", "x") => set_attribute(&mut self.x, attr.parse(value), session),
                expanded_name!("", "y") => set_attribute(&mut self.y, attr.parse(value), session),
                expanded_name!("", "width") => {
                    set_attribute(&mut self.width, attr.parse(value), session)
                }
                expanded_name!("", "height") => {
                    set_attribute(&mut self.height, attr.parse(value), session)
                }
                _ => (),
            }
        }
    }

    fn draw(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
        clipping: bool,
    ) -> DrawResult {
        if let Some(link) = self.link.as_ref() {
            let values = cascaded.get();
            let params = NormalizeParams::new(values, viewport);
            let rect = self.get_rect(&params);

            let use_node_name = format!("{node}");

            let stroke_paint = values.stroke().0.resolve(
                acquired_nodes,
                &use_node_name,
                values.stroke_opacity().0,
                values.color().0,
                cascaded.context_fill.clone(),
                cascaded.context_stroke.clone(),
                draw_ctx.session(),
            );

            let fill_paint = values.fill().0.resolve(
                acquired_nodes,
                &use_node_name,
                values.fill_opacity().0,
                values.color().0,
                cascaded.context_fill.clone(),
                cascaded.context_stroke.clone(),
                draw_ctx.session(),
            );

            draw_ctx.draw_from_use_node(
                node,
                acquired_nodes,
                values,
                rect,
                link,
                clipping,
                viewport,
                fill_paint,
                stroke_paint,
            )
        } else {
            Ok(viewport.empty_bbox())
        }
    }
}

/// The `<symbol>` element.
#[derive(Default)]
pub struct Symbol {
    preserve_aspect_ratio: AspectRatio,
    vbox: Option<ViewBox>,
}

impl Symbol {
    pub fn get_viewbox(&self) -> Option<ViewBox> {
        self.vbox
    }

    pub fn get_preserve_aspect_ratio(&self) -> AspectRatio {
        self.preserve_aspect_ratio
    }
}

impl ElementTrait for Symbol {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            match attr.expanded() {
                expanded_name!("", "preserveAspectRatio") => {
                    set_attribute(&mut self.preserve_aspect_ratio, attr.parse(value), session)
                }
                expanded_name!("", "viewBox") => {
                    set_attribute(&mut self.vbox, attr.parse(value), session)
                }
                _ => (),
            }
        }
    }
}

coord_units!(ClipPathUnits, CoordUnits::UserSpaceOnUse);

/// The `<clipPath>` element.
#[derive(Default)]
pub struct ClipPath {
    units: ClipPathUnits,
}

impl ClipPath {
    pub fn get_units(&self) -> CoordUnits {
        CoordUnits::from(self.units)
    }
}

impl ElementTrait for ClipPath {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            if attr.expanded() == expanded_name!("", "clipPathUnits") {
                set_attribute(&mut self.units, attr.parse(value), session);
            }
        }
    }
}

coord_units!(MaskUnits, CoordUnits::ObjectBoundingBox);
coord_units!(MaskContentUnits, CoordUnits::UserSpaceOnUse);

/// The `<mask>` element.
pub struct Mask {
    x: Length<Horizontal>,
    y: Length<Vertical>,
    width: ULength<Horizontal>,
    height: ULength<Vertical>,

    units: MaskUnits,
    content_units: MaskContentUnits,
}

impl Default for Mask {
    fn default() -> Mask {
        Mask {
            // these values are per the spec
            x: Length::<Horizontal>::parse_str("-10%").unwrap(),
            y: Length::<Vertical>::parse_str("-10%").unwrap(),
            width: ULength::<Horizontal>::parse_str("120%").unwrap(),
            height: ULength::<Vertical>::parse_str("120%").unwrap(),

            units: MaskUnits::default(),
            content_units: MaskContentUnits::default(),
        }
    }
}

impl Mask {
    pub fn get_units(&self) -> CoordUnits {
        CoordUnits::from(self.units)
    }

    pub fn get_content_units(&self) -> CoordUnits {
        CoordUnits::from(self.content_units)
    }

    pub fn get_rect(&self, params: &NormalizeParams) -> Rect {
        let x = self.x.to_user(params);
        let y = self.y.to_user(params);
        let w = self.width.to_user(params);
        let h = self.height.to_user(params);

        Rect::new(x, y, x + w, y + h)
    }
}

impl ElementTrait for Mask {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            match attr.expanded() {
                expanded_name!("", "x") => set_attribute(&mut self.x, attr.parse(value), session),
                expanded_name!("", "y") => set_attribute(&mut self.y, attr.parse(value), session),
                expanded_name!("", "width") => {
                    set_attribute(&mut self.width, attr.parse(value), session)
                }
                expanded_name!("", "height") => {
                    set_attribute(&mut self.height, attr.parse(value), session)
                }
                expanded_name!("", "maskUnits") => {
                    set_attribute(&mut self.units, attr.parse(value), session)
                }
                expanded_name!("", "maskContentUnits") => {
                    set_attribute(&mut self.content_units, attr.parse(value), session)
                }
                _ => (),
            }
        }
    }
}

/// The `<a>` element.
#[derive(Default)]
pub struct Link {
    pub link: Option<String>,
}

impl ElementTrait for Link {
    fn set_attributes(&mut self, attrs: &Attributes, _session: &Session) {
        for (attr, value) in attrs.iter() {
            let expanded = attr.expanded();
            if is_href(&expanded) {
                set_href(&expanded, &mut self.link, Some(value.to_owned()));
            }
        }
    }

    fn draw(
        &self,
        node: &Node,
        acquired_nodes: &mut AcquiredNodes<'_>,
        cascaded: &CascadedValues<'_>,
        viewport: &Viewport,
        draw_ctx: &mut DrawingCtx,
        _clipping: bool,
    ) -> DrawResult {
        // If this element is inside of <text>, do not draw it.
        // The <text> takes care of it.
        for an in node.ancestors() {
            if matches!(&*an.borrow_element_data(), ElementData::Text(_)) {
                return Ok(viewport.empty_bbox());
            }
        }

        let cascaded = CascadedValues::clone_with_node(cascaded, node);
        let values = cascaded.get();

        let elt = node.borrow_element();

        let link_is_empty = self.link.as_ref().map(|l| l.is_empty()).unwrap_or(true);

        let link_target = if link_is_empty {
            None
        } else {
            self.link.clone()
        };

        let stacking_ctx = Box::new(StackingContext::new_with_link(
            draw_ctx,
            acquired_nodes,
            &elt,
            values.transform(),
            values,
            viewport,
            link_target,
        ));

        draw_ctx.with_discrete_layer(
            &stacking_ctx,
            acquired_nodes,
            viewport,
            None,
            false,
            &mut |an, dc, new_viewport| node.draw_children(an, &cascaded, new_viewport, dc),
        )
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use crate::accept_language::UserLanguage;
    use crate::document::Document;
    use crate::dpi::Dpi;
    use crate::drawing_ctx::{RenderingConfiguration, SvgNesting};

    #[test]
    fn computes_group_extents() {
        let document = Document::load_from_bytes(
            br#"<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <g id="a">
    <g transform="translate(10, 10) scale(2, 3)">
      <rect x="0" y="0" width="5" height="10"/>
    </g>
    <rect x="0" y="0" width="5" height="10" transform="scale(2) translate(-10, -20)"/>
  </g>
</svg>
"#,
        );

        let a = document.lookup_internal_node("a").unwrap();

        let elt = a.borrow_element();

        let mut acquired_nodes = AcquiredNodes::new(&document, None);
        let cascaded = CascadedValues::new_from_node(&a);

        let dpi = Dpi::new(96.0, 96.0);

        let viewport = Viewport::new(dpi.clone(), 100.0, 100.0);

        let surface = cairo::RecordingSurface::create(cairo::Content::ColorAlpha, None).unwrap();
        let cr = cairo::Context::new(&surface).unwrap();

        let config = RenderingConfiguration {
            dpi,
            cancellable: None,
            user_language: UserLanguage::LanguageTags(crate::accept_language::LanguageTags::empty()),
            svg_nesting: SvgNesting::Standalone,
            measuring: false,
            testing: true,
        };

        let mut draw_ctx = DrawingCtx::new(Session::default(), &cr, &viewport, config, Vec::new());

        let layout = elt.layout(&a, &mut acquired_nodes, &cascaded, &viewport, &mut draw_ctx);

        match layout {
            Ok(Some(Layer {
                kind: LayerKind::Group(ref group),
                ..
            })) => {
                assert_eq!(group.extents, Some(Rect::new(-20.0, -40.0, 20.0, 40.0)));
            }

            Err(_) => panic!("layout should not produce an InternalRenderingError"),

            _ => panic!("layout object is not a LayerKind::Group"),
        }
    }
}

Coverage Report

Created: 2026-06-30 06:37