70 lines
2.5 KiB
Rust
70 lines
2.5 KiB
Rust
//! Preflight for vector exports, including subtrees rendered into embedded images.
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use figcraft_doc::{Document, NodeId};
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/// Maximum descendant depth for SVG/PDF export; each selected root is at depth zero.
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pub const MAX_EXPORT_DEPTH: usize = 256;
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/// Exporting this visible subtree would silently omit content at the traversal limit.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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pub struct ExportDepthError {
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pub root: NodeId,
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pub node: NodeId,
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}
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impl std::fmt::Display for ExportDepthError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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write!(
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f,
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"cannot export layer {}: layer {} exceeds the maximum export depth of {MAX_EXPORT_DEPTH}; select an inner layer or reduce nesting",
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self.root, self.node
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)
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}
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}
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impl std::error::Error for ExportDepthError {}
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/// Refuse a visible descendant deeper than [`MAX_EXPORT_DEPTH`] before computing bounds or
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/// drawing. Hidden subtrees are not exported. Masks, boolean operands and rasterised effects
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/// still depend on their descendants, so they participate in the same preflight.
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///
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/// The walk uses one iterator per ancestor (bounded auxiliary memory), rather than recursion or
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/// collecting a whole subtree. A cycle also reaches the depth limit and is refused.
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pub fn check_export_depth(doc: &Document, roots: &[NodeId]) -> Result<(), ExportDepthError> {
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for root in roots {
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let mut stack = vec![(std::slice::from_ref(root).iter(), 0)];
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while let Some((siblings, depth)) = stack.last_mut() {
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let Some(&id) = siblings.next() else {
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stack.pop();
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continue;
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};
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let depth = *depth;
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let Some(node) = doc.node(id) else { continue };
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if !node.visible {
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continue;
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}
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if depth > MAX_EXPORT_DEPTH {
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return Err(ExportDepthError { root: *root, node: id });
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}
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if !node.children.is_empty() {
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stack.push((node.children.iter(), depth + 1));
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}
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}
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}
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Ok(())
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use figcraft_doc::NodeKind;
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#[test]
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fn export_depth_preflight_refuses_a_cyclic_subtree() {
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let mut doc = Document::new("cycle");
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let root = doc.create(doc.first_page().unwrap(), NodeKind::Group, "root", 0.0, 0.0, 1.0, 1.0).unwrap();
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doc.get_mut(root).unwrap().children.push(root);
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assert_eq!(check_export_depth(&doc, &[root]), Err(ExportDepthError { root, node: root }));
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}
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}
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