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/// PDF Linear Element Renderer
///
/// This module handles the rendering of DucLinearElement to PDF operations.
/// It translates the Vello renderer's BezPath logic into PDF path construction
/// commands, supporting:
/// - Straight lines and Bezier curves (quadratic and cubic)
/// - Closed and open paths
/// - Fill paths with minimal cycles (faces)
/// - Stroke paths with all segments
/// - Path overrides for selective styling
use crate::ConversionResult;
use duc::types::{DucLine, DucLinearElement, DucPoint, GeometricPoint};
use hipdf::lopdf::{content::Operation, Object};
use std::collections::{BTreeMap, HashSet};
pub struct PdfLinearRenderer;
impl PdfLinearRenderer {
/// Stream a linear element to PDF operations
pub fn stream_linear(linear: &DucLinearElement) -> ConversionResult<Vec<Operation>> {
let mut ops = Vec::new();
let points = &linear.linear_base.points;
let lines = &linear.linear_base.lines;
if points.is_empty() || lines.is_empty() {
return Ok(ops);
}
// Create stroke path (all segments)
let stroke_path_ops = Self::create_stroke_path(points, lines)?;
// Create fill paths (minimal closed loops only)
let fill_paths_ops = Self::create_fill_paths(points, lines)?;
// Determine what to render based on styles
let has_background = !linear.linear_base.base.styles.background.is_empty();
let has_stroke = !linear.linear_base.base.styles.stroke.is_empty();
if has_background && !fill_paths_ops.is_empty() {
// Render fills first
ops.extend(fill_paths_ops);
if has_stroke {
// Then render strokes on top
ops.extend(stroke_path_ops);
}
} else if has_stroke {
// Stroke only
ops.extend(stroke_path_ops);
}
Ok(ops)
}
/// Transform a Duc point from the top-left DUC system to PDF local coordinates
/// (origin at top-left after the element translation, positive Y upwards in PDF)
fn transform_point_to_pdf(point: &DucPoint) -> (f64, f64) {
(point.x, -point.y)
}
/// Transform a geometric control point to PDF local coordinates
fn transform_handle_to_pdf(handle: &GeometricPoint) -> (f64, f64) {
(handle.x, -handle.y)
}
/// Create PDF path operations for stroking (includes all line segments)
fn create_stroke_path(
points: &[DucPoint],
lines: &[DucLine],
) -> ConversionResult<Vec<Operation>> {
let mut ops = Vec::new();
if points.is_empty() || lines.is_empty() {
return Ok(ops);
}
// Track which lines have been consumed
let mut visited = vec![false; lines.len()];
for i in 0..lines.len() {
if visited[i] {
continue;
}
let mut current_line_idx = i;
let first_line_idx = i;
let mut subpath_started = false;
loop {
let line = &lines[current_line_idx];
visited[current_line_idx] = true;
// Validate indices
let s_idx = line.start.index;
let e_idx = line.end.index;
if s_idx < 0
|| e_idx < 0
|| s_idx >= points.len() as i32
|| e_idx >= points.len() as i32
{
break;
}
if !subpath_started {
// Start new subpath
let start_point = &points[s_idx as usize];
let (start_x, start_y) = Self::transform_point_to_pdf(start_point);
ops.push(Operation::new(
"m",
vec![Object::Real(start_x as f32), Object::Real(start_y as f32)],
));
subpath_started = true;
}
// Add segment (line or curve)
let start_point = &points[s_idx as usize];
let end_point = &points[e_idx as usize];
ops.extend(Self::add_segment(
start_point,
end_point,
&line.start.handle,
&line.end.handle,
)?);
// Try to find next connected line
let mut next_line_opt = None;
for (idx, next_line) in lines.iter().enumerate() {
if visited[idx] {
continue;
}
if next_line.start.index == e_idx {
next_line_opt = Some(idx);
break;
}
}
match next_line_opt {
Some(next_idx) => {
current_line_idx = next_idx;
}
None => {
// Check if we should close the path
let first_line = &lines[first_line_idx];
if e_idx == first_line.start.index {
ops.push(Operation::new("h", vec![])); // Close path
}
break;
}
}
}
}
// Stroke the path
ops.push(Operation::new("S", vec![]));
Ok(ops)
}
/// Create PDF path operations for filling (minimal closed loops only)
fn create_fill_paths(
points: &[DucPoint],
lines: &[DucLine],
) -> ConversionResult<Vec<Operation>> {
let mut ops = Vec::new();
if points.is_empty() || lines.is_empty() {
return Ok(ops);
}
// Build undirected adjacency list
let mut adj: BTreeMap<i32, Vec<(i32, &DucLine, usize)>> = BTreeMap::new();
for (line_idx, line) in lines.iter().enumerate() {
let start = line.start.index;
let end = line.end.index;
if start >= 0 && end >= 0 && start < points.len() as i32 && end < points.len() as i32 {
adj.entry(start).or_default().push((end, line, line_idx));
adj.entry(end).or_default().push((start, line, line_idx));
}
}
let mut found_cycles = HashSet::new();
// Find all minimal cycles
for start_node_idx in adj.keys().copied() {
let mut stack = vec![(start_node_idx, vec![start_node_idx], vec![])];
while let Some((current_node_idx, path, used_line_indices)) = stack.pop() {
if path.len() > points.len() {
continue;
}
if let Some(neighbors) = adj.get(¤t_node_idx) {
for (neighbor_idx, _line, line_idx) in neighbors {
// Avoid immediate backtracking
if path.len() >= 2 && *neighbor_idx == path[path.len() - 2] {
continue;
}
// Found a cycle
if *neighbor_idx == start_node_idx && path.len() >= 2 {
let cycle_nodes = path.clone();
let mut cycle_line_indices = used_line_indices.clone();
cycle_line_indices.push(*line_idx);
// Check if cycle is minimal (no shortcuts)
let mut is_minimal = true;
let cycle_len = cycle_nodes.len();
if cycle_len > 2 {
for i in 0..cycle_len {
for j in (i + 1)..cycle_len {
let u = cycle_nodes[i];
let v = cycle_nodes[j];
let is_adjacent_in_cycle =
(j == i + 1) || (i == 0 && j == cycle_len - 1);
if !is_adjacent_in_cycle {
if let Some(neighbors_of_u) = adj.get(&u) {
if neighbors_of_u.iter().any(|(n, _, _)| *n == v) {
is_minimal = false;
break;
}
}
}
}
if !is_minimal {
break;
}
}
}
if is_minimal {
let mut canonical_cycle = cycle_nodes.clone();
canonical_cycle.sort_unstable();
if !found_cycles.contains(&canonical_cycle) {
found_cycles.insert(canonical_cycle);
// Render this cycle
let mut render_path_nodes = cycle_nodes;
render_path_nodes.push(start_node_idx);
// Start path at first node
let start_point = &points[render_path_nodes[0] as usize];
let (start_x, start_y) =
Self::transform_point_to_pdf(start_point);
ops.push(Operation::new(
"m",
vec![
Object::Real(start_x as f32),
Object::Real(start_y as f32),
],
));
// Add segments for cycle
for i in 0..(render_path_nodes.len() - 1) {
let p1_idx = render_path_nodes[i];
let p2_idx = render_path_nodes[i + 1];
if let Some((_, connecting_line, _)) =
adj.get(&p1_idx).and_then(|n| {
n.iter().find(|(idx, _, _)| *idx == p2_idx)
})
{
let p1 = &points[p1_idx as usize];
let p2 = &points[p2_idx as usize];
let (start_handle, end_handle) =
if connecting_line.start.index == p1_idx {
(
&connecting_line.start.handle,
&connecting_line.end.handle,
)
} else {
(
&connecting_line.end.handle,
&connecting_line.start.handle,
)
};
ops.extend(Self::add_segment(
p1,
p2,
start_handle,
end_handle,
)?);
}
}
// Close the cycle
ops.push(Operation::new("h", vec![]));
}
}
} else if !path.contains(neighbor_idx) {
let mut new_path = path.clone();
new_path.push(*neighbor_idx);
let mut new_line_indices = used_line_indices.clone();
new_line_indices.push(*line_idx);
stack.push((*neighbor_idx, new_path, new_line_indices));
}
}
}
}
}
if !ops.is_empty() {
// Fill using even-odd rule (matches Vello's EvenOdd fill)
ops.push(Operation::new("f*", vec![])); // f* = fill with even-odd rule
}
Ok(ops)
}
/// Add a segment to the path (line or Bezier curve)
fn add_segment(
start_point: &DucPoint,
end_point: &DucPoint,
start_handle: &Option<GeometricPoint>,
end_handle: &Option<GeometricPoint>,
) -> ConversionResult<Vec<Operation>> {
let mut ops = Vec::new();
let (p3_x, p3_y) = Self::transform_point_to_pdf(end_point);
match (start_handle, end_handle) {
// Cubic Bezier curve (both handles present)
(Some(start_h), Some(end_h))
if start_h.x.is_finite()
&& start_h.y.is_finite()
&& end_h.x.is_finite()
&& end_h.y.is_finite() =>
{
let (cp1_x, cp1_y) = Self::transform_handle_to_pdf(start_h);
let (cp2_x, cp2_y) = Self::transform_handle_to_pdf(end_h);
if cp1_x.is_finite() && cp1_y.is_finite() && cp2_x.is_finite() && cp2_y.is_finite()
{
ops.push(Operation::new(
"c",
vec![
Object::Real(cp1_x as f32),
Object::Real(cp1_y as f32),
Object::Real(cp2_x as f32),
Object::Real(cp2_y as f32),
Object::Real(p3_x as f32),
Object::Real(p3_y as f32),
],
));
} else {
ops.push(Operation::new(
"l",
vec![Object::Real(p3_x as f32), Object::Real(p3_y as f32)],
));
}
}
// Quadratic curve (single handle) - convert to cubic
_ if start_handle.is_some() || end_handle.is_some() => {
if let Some(h) = start_handle.as_ref().or(end_handle.as_ref()) {
// Convert quadratic to cubic using original coordinates, then transform the result.
// cp1 = p0 + 2/3 * (c - p0)
let cp1_x_orig = start_point.x + (2.0 / 3.0) * (h.x - start_point.x);
let cp1_y_orig = start_point.y + (2.0 / 3.0) * (h.y - start_point.y);
// cp2 = p3 + 2/3 * (c - p3)
let cp2_x_orig = end_point.x + (2.0 / 3.0) * (h.x - end_point.x);
let cp2_y_orig = end_point.y + (2.0 / 3.0) * (h.y - end_point.y);
// Now transform the final control points to PDF coordinates
let (cp1_x, cp1_y) = Self::transform_handle_to_pdf(&GeometricPoint {
x: cp1_x_orig,
y: cp1_y_orig,
});
let (cp2_x, cp2_y) = Self::transform_handle_to_pdf(&GeometricPoint {
x: cp2_x_orig,
y: cp2_y_orig,
});
if cp1_x.is_finite()
&& cp1_y.is_finite()
&& cp2_x.is_finite()
&& cp2_y.is_finite()
{
ops.push(Operation::new(
"c",
vec![
Object::Real(cp1_x as f32),
Object::Real(cp1_y as f32),
Object::Real(cp2_x as f32),
Object::Real(cp2_y as f32),
Object::Real(p3_x as f32),
Object::Real(p3_y as f32),
],
));
} else {
// Fallback to straight line
ops.push(Operation::new(
"l",
vec![Object::Real(p3_x as f32), Object::Real(p3_y as f32)],
));
}
}
}
// Straight line
_ => {
ops.push(Operation::new(
"l",
vec![Object::Real(p3_x as f32), Object::Real(p3_y as f32)],
));
}
}
Ok(ops)
}
}