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Implement the winding fill rule for real

This commit is contained in:
Patrick Walton 2017-09-18 15:34:36 -07:00
parent e5f9b56a1d
commit dbd83d17ef
2 changed files with 41 additions and 3 deletions
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2
partitioner/src/lib.rs
View File

@ -33,7 +33,7 @@ pub mod legalizer;
pub mod partitioner;
#[repr(C)]
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub enum FillRule {
EvenOdd = 0,
Winding = 1,

42
partitioner/src/partitioner.rs
View File

@ -466,6 +466,14 @@ impl<'a> Partitioner<'a> {
active_edge_index > 0 && self.should_fill_below_active_edge(active_edge_index - 1)
}
fn winding_number_above_active_edge(&self, active_edge_index: u32) -> i32 {
if active_edge_index == 0 {
0
} else {
self.winding_number_below_active_edge(active_edge_index - 1)
}
}
fn winding_number_below_active_edge(&self, active_edge_index: u32) -> i32 {
let mut winding_number = 0;
for active_edge_index in 0..(active_edge_index as usize + 1) {
@ -479,14 +487,44 @@ impl<'a> Partitioner<'a> {
}
fn emit_b_quad_below(&mut self, upper_active_edge_index: u32, right_x: f32) {
self.emit_b_quad_above(upper_active_edge_index + 1, right_x)
let mut lower_active_edge_index = upper_active_edge_index + 1;
if self.fill_rule == FillRule::Winding {
let active_edge_count = self.active_edges.len() as u32;
let mut winding_number =
self.winding_number_below_active_edge(lower_active_edge_index);
while lower_active_edge_index + 1 < active_edge_count && winding_number != 0 {
lower_active_edge_index += 1;
if self.active_edges[lower_active_edge_index as usize].left_to_right {
winding_number += 1
} else {
winding_number -= 1
}
}
}
self.emit_b_quad_above(lower_active_edge_index, right_x)
}
fn emit_b_quad_above(&mut self, lower_active_edge_index: u32, right_x: f32) {
// TODO(pcwalton): Assert that the green X position is the same on both edges.
debug_assert!(lower_active_edge_index > 0,
"Can't emit b_quads above the top active edge");
let upper_active_edge_index = lower_active_edge_index - 1;
let mut upper_active_edge_index = lower_active_edge_index - 1;
if self.fill_rule == FillRule::Winding {
let mut winding_number =
self.winding_number_above_active_edge(upper_active_edge_index);
while upper_active_edge_index > 0 && winding_number != 0 {
upper_active_edge_index -= 1;
if self.active_edges[upper_active_edge_index as usize].left_to_right {
winding_number -= 1
} else {
winding_number += 1
}
}
}
let upper_curve = self.subdivide_active_edge_at(upper_active_edge_index, right_x);
let lower_curve = self.subdivide_active_edge_at(lower_active_edge_index, right_x);