librsvg 2.62.2

A library to render SVG images to Cairo surfaces. GNOME uses this to render SVG icons. Outside of GNOME, other desktop environments use it for similar purposes. Wikimedia uses it for Wikipedia's SVG diagrams.
Documentation
//! The `filter` element.

use cssparser::Parser;
use markup5ever::{expanded_name, local_name, ns};
use std::slice::Iter;

use crate::color::Color;
use crate::coord_units::CoordUnits;
use crate::document::{AcquiredNodes, NodeId};
use crate::drawing_ctx::Viewport;
use crate::element::{ElementData, ElementTrait, set_attribute};
use crate::error::ValueErrorKind;
use crate::filter_func::FilterFunction;
use crate::filters::{FilterResolveError, FilterSpec};
use crate::length::*;
use crate::node::{Node, NodeBorrow};
use crate::parsers::{Parse, ParseValue};
use crate::rect::Rect;
use crate::rsvg_log;
use crate::session::Session;
use crate::xml::Attributes;
use crate::{borrow_element_as, is_element_of_type};

/// The `<filter>` node.
pub struct Filter {
    x: Length<Horizontal>,
    y: Length<Vertical>,
    width: ULength<Horizontal>,
    height: ULength<Vertical>,
    filter_units: CoordUnits,
    primitive_units: CoordUnits,
}

/// A `<filter>` element definition in user-space coordinates.
pub struct UserSpaceFilter {
    pub rect: Rect,
    pub filter_units: CoordUnits,
    pub primitive_units: CoordUnits,
}

impl Default for Filter {
    /// Constructs a new `Filter` with default properties.
    fn default() -> Self {
        Self {
            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(),
            filter_units: CoordUnits::ObjectBoundingBox,
            primitive_units: CoordUnits::UserSpaceOnUse,
        }
    }
}

impl Filter {
    pub fn get_filter_units(&self) -> CoordUnits {
        self.filter_units
    }

    pub fn to_user_space(&self, params: &NormalizeParams) -> UserSpaceFilter {
        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);

        let rect = Rect::new(x, y, x + w, y + h);

        UserSpaceFilter {
            rect,
            filter_units: self.filter_units,
            primitive_units: self.primitive_units,
        }
    }
}

impl ElementTrait for Filter {
    fn set_attributes(&mut self, attrs: &Attributes, session: &Session) {
        for (attr, value) in attrs.iter() {
            match attr.expanded() {
                expanded_name!("", "filterUnits") => {
                    set_attribute(&mut self.filter_units, attr.parse(value), session)
                }
                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!("", "primitiveUnits") => {
                    set_attribute(&mut self.primitive_units, attr.parse(value), session)
                }
                _ => (),
            }
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub enum FilterValue {
    Url(NodeId),
    Function(FilterFunction),
}

impl FilterValue {
    pub fn to_filter_spec(
        &self,
        acquired_nodes: &mut AcquiredNodes<'_>,
        user_space_params: &NormalizeParams,
        current_color: Color,
        viewport: &Viewport,
        session: &Session,
        node_being_filtered_name: &str,
    ) -> Result<FilterSpec, FilterResolveError> {
        match *self {
            FilterValue::Url(ref node_id) => filter_spec_from_filter_node(
                acquired_nodes,
                viewport,
                session,
                node_id,
                node_being_filtered_name,
            ),

            FilterValue::Function(ref func) => {
                Ok(func.to_filter_spec(user_space_params, current_color))
            }
        }
    }
}

/// Holds the viewport parameters for both objectBoundingBox and userSpaceOnUse units.
///
/// When collecting a set of filter primitives (`feFoo`) into a [`FilterSpec`], which is
/// in user space, we need to convert each primitive's units into user space units.  So,
/// pre-compute both cases and pass them around.
///
/// This struct needs a better name; I didn't want to make it seem specific to filters by
/// calling `FiltersViewport` or `FilterCollectionProcessViewport`.  Maybe the
/// original [`Viewport`] should be this struct, with both cases included...
struct ViewportGen {
    object_bounding_box: Viewport,
    user_space_on_use: Viewport,
}

impl ViewportGen {
    pub fn new(viewport: &Viewport) -> Self {
        ViewportGen {
            object_bounding_box: viewport.with_units(CoordUnits::ObjectBoundingBox),
            user_space_on_use: viewport.with_units(CoordUnits::UserSpaceOnUse),
        }
    }

    fn get(&self, units: CoordUnits) -> &Viewport {
        match units {
            CoordUnits::ObjectBoundingBox => &self.object_bounding_box,
            CoordUnits::UserSpaceOnUse => &self.user_space_on_use,
        }
    }
}

fn extract_filter_from_filter_node(
    filter_node: &Node,
    acquired_nodes: &mut AcquiredNodes<'_>,
    session: &Session,
    filter_viewport: &ViewportGen,
) -> Result<FilterSpec, FilterResolveError> {
    assert!(is_element_of_type!(filter_node, Filter));

    let filter_element = filter_node.borrow_element();

    let user_space_filter = {
        let filter_values = filter_element.get_computed_values();

        let filter = borrow_element_as!(filter_node, Filter);

        filter.to_user_space(&NormalizeParams::new(
            filter_values,
            filter_viewport.get(filter.get_filter_units()),
        ))
    };

    let primitive_viewport = filter_viewport.get(user_space_filter.primitive_units);

    let primitive_nodes = filter_node
        .children()
        .filter(|c| c.is_element())
        // Keep only filter primitives (those that implement the Filter trait)
        .filter(|c| c.borrow_element().as_filter_effect().is_some());

    let mut user_space_primitives = Vec::new();

    for primitive_node in primitive_nodes {
        let elt = primitive_node.borrow_element();
        let effect = elt.as_filter_effect().unwrap();

        let primitive_name = format!("{primitive_node}");

        let primitive_values = elt.get_computed_values();
        let params = NormalizeParams::new(primitive_values, primitive_viewport);

        let primitives = match effect.resolve(acquired_nodes, &primitive_node) {
            Ok(primitives) => primitives,
            Err(e) => {
                rsvg_log!(
                    session,
                    "(filter primitive {} returned an error: {})",
                    primitive_name,
                    e
                );
                return Err(e);
            }
        };

        for p in primitives {
            user_space_primitives.push(p.into_user_space(&params));
        }
    }

    Ok(FilterSpec {
        name: filter_element
            .get_id()
            .unwrap_or("(filter element without id)")
            .to_string(),
        user_space_filter,
        primitives: user_space_primitives,
    })
}

fn filter_spec_from_filter_node(
    acquired_nodes: &mut AcquiredNodes<'_>,
    viewport: &Viewport,
    session: &Session,
    node_id: &NodeId,
    node_being_filtered_name: &str,
) -> Result<FilterSpec, FilterResolveError> {
    let filter_viewport = ViewportGen::new(viewport);

    acquired_nodes
        .acquire(node_id)
        .map_err(|e| {
            rsvg_log!(
                *session,
                "element {} will not be filtered with \"{}\": {}",
                node_being_filtered_name,
                node_id,
                e
            );
            FilterResolveError::ReferenceToNonFilterElement
        })
        .and_then(|acquired| {
            let node = acquired.get();

            match *node.borrow_element_data() {
                ElementData::Filter(_) => {
                    extract_filter_from_filter_node(node, acquired_nodes, session, &filter_viewport)
                }

                _ => {
                    rsvg_log!(
                        *session,
                        "element {} will not be filtered since \"{}\" is not a filter",
                        node_being_filtered_name,
                        node_id,
                    );
                    Err(FilterResolveError::ReferenceToNonFilterElement)
                }
            }
        })
}

#[derive(Debug, Default, Clone, PartialEq)]
pub struct FilterValueList(Vec<FilterValue>);

impl FilterValueList {
    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }

    pub fn iter(&self) -> Iter<'_, FilterValue> {
        self.0.iter()
    }
}

impl Parse for FilterValueList {
    fn parse<'i>(parser: &mut Parser<'i, '_>) -> Result<Self, crate::error::ParseError<'i>> {
        let mut result = FilterValueList::default();

        loop {
            let loc = parser.current_source_location();

            let filter_value = if let Ok(func) = parser.try_parse(|p| FilterFunction::parse(p)) {
                FilterValue::Function(func)
            } else {
                let url = parser.expect_url()?;
                let node_id = NodeId::parse(&url)
                    .map_err(|e| loc.new_custom_error(ValueErrorKind::from(e)))?;

                FilterValue::Url(node_id)
            };

            result.0.push(filter_value);

            if parser.is_exhausted() {
                break;
            }
        }

        Ok(result)
    }
}

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

    #[test]
    fn parses_filter_value_list() {
        let n1 = NodeId::External("foo.svg".to_string(), "bar".to_string());
        let n2 = NodeId::External("test.svg".to_string(), "baz".to_string());
        assert_eq!(
            FilterValueList::parse_str("url(foo.svg#bar) url(test.svg#baz)").unwrap(),
            FilterValueList(vec![FilterValue::Url(n1), FilterValue::Url(n2)])
        );
    }

    #[test]
    fn detects_invalid_filter_value_list() {
        assert!(FilterValueList::parse_str("none").is_err());
        assert!(FilterValueList::parse_str("").is_err());
        assert!(FilterValueList::parse_str("fail").is_err());
        assert!(FilterValueList::parse_str("url(#test) none").is_err());
    }
}