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//! Generic adapter connecting a vertex source to a vertex generator.
//!
//! Port of `agg_conv_adaptor_vcgen.h` — the core adapter pattern used by
//! `ConvStroke`, `ConvDash`, and `ConvContour`.
use crate::basics::{
is_end_poly, is_move_to, is_stop, is_vertex, VertexSource, PATH_CMD_MOVE_TO, PATH_CMD_STOP,
};
// ============================================================================
// VcgenGenerator trait
// ============================================================================
/// Vertex generator interface used by `ConvAdaptorVcgen`.
///
/// Port of the implicit C++ "Generator" concept used by `conv_adaptor_vcgen`.
pub trait VcgenGenerator {
fn remove_all(&mut self);
fn add_vertex(&mut self, x: f64, y: f64, cmd: u32);
fn rewind(&mut self, path_id: u32);
fn vertex(&mut self, x: &mut f64, y: &mut f64) -> u32;
}
// ============================================================================
// ConvAdaptorVcgen
// ============================================================================
#[derive(Debug, Clone, Copy, PartialEq)]
enum Status {
Initial,
Accumulate,
Generate,
}
/// Generic adapter connecting a `VertexSource` to a `VcgenGenerator`.
///
/// Reads vertices from the source, feeds them to the generator, then
/// yields the generated vertices. Handles path splitting on `move_to`.
///
/// Port of C++ `conv_adaptor_vcgen<VertexSource, Generator, Markers>`.
/// Markers omitted (null_markers behavior).
pub struct ConvAdaptorVcgen<VS: VertexSource, Gen: VcgenGenerator> {
source: VS,
generator: Gen,
status: Status,
last_cmd: u32,
start_x: f64,
start_y: f64,
}
impl<VS: VertexSource, Gen: VcgenGenerator> ConvAdaptorVcgen<VS, Gen> {
pub fn new(source: VS, generator: Gen) -> Self {
Self {
source,
generator,
status: Status::Initial,
last_cmd: 0,
start_x: 0.0,
start_y: 0.0,
}
}
pub fn generator(&self) -> &Gen {
&self.generator
}
pub fn generator_mut(&mut self) -> &mut Gen {
&mut self.generator
}
pub fn source(&self) -> &VS {
&self.source
}
pub fn source_mut(&mut self) -> &mut VS {
&mut self.source
}
}
impl<VS: VertexSource, Gen: VcgenGenerator> VertexSource for ConvAdaptorVcgen<VS, Gen> {
fn rewind(&mut self, path_id: u32) {
self.source.rewind(path_id);
self.status = Status::Initial;
}
fn vertex(&mut self, x: &mut f64, y: &mut f64) -> u32 {
loop {
match self.status {
Status::Initial => {
// null_markers.remove_all() — no-op
self.last_cmd = self.source.vertex(&mut self.start_x, &mut self.start_y);
self.status = Status::Accumulate;
// fall through to Accumulate
}
Status::Accumulate => {
if is_stop(self.last_cmd) {
return PATH_CMD_STOP;
}
self.generator.remove_all();
self.generator
.add_vertex(self.start_x, self.start_y, PATH_CMD_MOVE_TO);
// null_markers.add_vertex(...) — no-op
loop {
let cmd = self.source.vertex(x, y);
if is_vertex(cmd) {
self.last_cmd = cmd;
if is_move_to(cmd) {
self.start_x = *x;
self.start_y = *y;
break;
}
self.generator.add_vertex(*x, *y, cmd);
// null_markers.add_vertex(*x, *y, PATH_CMD_LINE_TO) — no-op
} else {
if is_stop(cmd) {
self.last_cmd = PATH_CMD_STOP;
break;
}
if is_end_poly(cmd) {
self.generator.add_vertex(*x, *y, cmd);
break;
}
}
}
self.generator.rewind(0);
self.status = Status::Generate;
// fall through to Generate
}
Status::Generate => {
let cmd = self.generator.vertex(x, y);
if is_stop(cmd) {
// Generator exhausted — go back to Accumulate for next sub-path
self.status = Status::Accumulate;
continue;
}
return cmd;
}
}
}
}
}
// ============================================================================
// Tests
// ============================================================================
#[cfg(test)]
mod tests {
use super::*;
use crate::basics::PATH_CMD_STOP;
/// Minimal generator that echoes input as-is.
struct EchoGenerator {
vertices: Vec<(f64, f64, u32)>,
idx: usize,
}
impl EchoGenerator {
fn new() -> Self {
Self {
vertices: Vec::new(),
idx: 0,
}
}
}
impl VcgenGenerator for EchoGenerator {
fn remove_all(&mut self) {
self.vertices.clear();
}
fn add_vertex(&mut self, x: f64, y: f64, cmd: u32) {
self.vertices.push((x, y, cmd));
}
fn rewind(&mut self, _path_id: u32) {
self.idx = 0;
}
fn vertex(&mut self, x: &mut f64, y: &mut f64) -> u32 {
if self.idx >= self.vertices.len() {
return PATH_CMD_STOP;
}
let (vx, vy, cmd) = self.vertices[self.idx];
*x = vx;
*y = vy;
self.idx += 1;
cmd
}
}
#[test]
fn test_empty_source() {
use crate::path_storage::PathStorage;
let path = PathStorage::new();
let mut adaptor = ConvAdaptorVcgen::new(path, EchoGenerator::new());
adaptor.rewind(0);
let (mut x, mut y) = (0.0, 0.0);
let cmd = adaptor.vertex(&mut x, &mut y);
assert_eq!(cmd, PATH_CMD_STOP);
}
#[test]
fn test_passthrough_with_echo() {
use crate::path_storage::PathStorage;
let mut path = PathStorage::new();
path.move_to(10.0, 20.0);
path.line_to(30.0, 40.0);
let mut adaptor = ConvAdaptorVcgen::new(path, EchoGenerator::new());
adaptor.rewind(0);
let mut verts = Vec::new();
loop {
let (mut x, mut y) = (0.0, 0.0);
let cmd = adaptor.vertex(&mut x, &mut y);
if is_stop(cmd) {
break;
}
verts.push((x, y, cmd));
}
assert!(
verts.len() >= 2,
"Expected >= 2 vertices, got {}",
verts.len()
);
}
#[test]
fn test_generator_access() {
use crate::path_storage::PathStorage;
let path = PathStorage::new();
let adaptor = ConvAdaptorVcgen::new(path, EchoGenerator::new());
let _ = adaptor.generator();
}
}