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use crate::path_builder::*;
use crate::Point;
use lyon_geom::LineSegment;
#[derive(Clone, Copy)]
struct DashState {
index: usize, // index into the dash array
on: bool, // whether the dash is on or off
remaining_length: f32, // how much of the dash remains
}
pub fn dash_path(path: &Path, dash_array: &[f32], mut dash_offset: f32) -> Path {
let mut dashed = PathBuilder::new();
let mut cur_pt = None;
let mut start_point = None;
let mut total_dash_length = 0.;
for dash in dash_array {
total_dash_length += *dash;
}
if dash_array.len() % 2 == 1 {
// if the number of items in the dash_array is odd then we need it takes two periods
// to return to the beginning.
total_dash_length *= 2.;
}
// The dash length must be more than zero.
if !(total_dash_length > 0.) {
return dashed.finish();
}
// Handle large positive and negative offsets so that we don't loop for a high number of
// iterations below in extreme cases
dash_offset = dash_offset % total_dash_length;
if dash_offset < 0. {
dash_offset += total_dash_length;
}
// To handle closed paths we need a bunch of extra state so that we properly
// join the first segment. Unfortunately, this makes the code sort of hairy.
// We need to store all of the points in the initial segment so that we can
// join the end of the path with it.
let mut is_first_segment = true;
let mut first_dash = true;
let mut initial_segment : Vec<Point> = Vec::new();
let mut state = DashState {
on: true,
remaining_length: dash_array[0],
index: 0,
};
// adjust our position in the dash array by the dash offset
while dash_offset > state.remaining_length {
dash_offset -= state.remaining_length;
state.index += 1;
state.remaining_length = dash_array[state.index % dash_array.len()];
state.on = !state.on;
}
state.remaining_length -= dash_offset;
// Save a copy of the initial state so that we can restore it for each subpath
let initial = state;
for op in &path.ops {
match *op {
PathOp::MoveTo(pt) => {
cur_pt = Some(pt);
start_point = Some(pt);
dashed.move_to(pt.x, pt.y);
// flush the previous initial segment
if initial_segment.len() > 0 {
dashed.move_to(initial_segment[0].x, initial_segment[0].y);
for i in 1..initial_segment.len() {
dashed.line_to(initial_segment[i].x, initial_segment[i].y);
}
}
is_first_segment = true;
initial_segment = Vec::new();
first_dash = true;
// reset the dash state
state = initial;
}
PathOp::LineTo(pt) => {
if let Some(cur_pt) = cur_pt {
let mut start = cur_pt;
let line = LineSegment {
from: start,
to: pt,
};
let mut len = line.length();
let lv = line.to_vector().normalize();
while len > state.remaining_length {
let seg = start + lv * state.remaining_length;
if state.on {
if is_first_segment {
initial_segment.push(start);
initial_segment.push(seg);
} else {
dashed.line_to(seg.x, seg.y);
}
} else {
first_dash = false;
dashed.move_to(seg.x, seg.y);
}
is_first_segment = false;
state.on = !state.on;
state.index += 1;
len -= state.remaining_length;
state.remaining_length = dash_array[state.index % dash_array.len()];
start = seg;
}
if state.on {
if is_first_segment {
initial_segment.push(start);
initial_segment.push(pt);
} else {
dashed.line_to(pt.x, pt.y);
}
} else {
first_dash = false;
dashed.move_to(pt.x, pt.y);
}
state.remaining_length -= len;
}
cur_pt = Some(pt);
}
PathOp::Close => {
if let (Some(current), Some(start_point)) = (cur_pt, start_point) {
let mut start = current;
let line = LineSegment {
from: start,
to: start_point,
};
let mut len = line.length();
let lv = line.to_vector().normalize();
while len > state.remaining_length {
let seg = start + lv * state.remaining_length;
if state.on {
if is_first_segment {
initial_segment.push(start);
initial_segment.push(seg);
} else {
dashed.line_to(seg.x, seg.y);
}
} else {
first_dash = false;
dashed.move_to(seg.x, seg.y);
}
state.on = !state.on;
state.index += 1;
len -= state.remaining_length;
state.remaining_length = dash_array[state.index % dash_array.len()];
start = seg;
}
if state.on {
if first_dash {
// If we're still on the first dash we can just close
dashed.close();
} else {
if initial_segment.len() > 0 {
// If have an initial segment we'll need to connect with it
for pt in initial_segment {
dashed.line_to(pt.x, pt.y);
}
} else {
dashed.line_to(start_point.x, start_point.y);
}
}
} else {
if initial_segment.len() > 0 {
dashed.move_to(initial_segment[0].x, initial_segment[0].y);
for i in 1..initial_segment.len() {
dashed.line_to(initial_segment[i].x, initial_segment[i].y);
}
}
}
initial_segment = Vec::new();
cur_pt = Some(start_point);
// reset the dash state
state = initial;
} else {
cur_pt = None;
}
}
PathOp::QuadTo(..) => panic!("Only flat paths handled"),
PathOp::CubicTo(..) => panic!("Only flat paths handled"),
}
}
// We still have an initial segment that we need to emit
if !initial_segment.is_empty() {
dashed.move_to(initial_segment[0].x, initial_segment[0].y);
for i in 1..initial_segment.len() {
dashed.line_to(initial_segment[i].x, initial_segment[i].y);
}
}
dashed.finish()
}