Fix clipping

geometry/src/clip.rs

@@ -11,6 +11,9 @@
 use crate::line_segment::LineSegmentF32;
 use crate::outline::{Contour, PointFlags};
 use crate::point::Point2DF32;
+use crate::segment::Segment;
+use crate::util::lerp;
+use arrayvec::ArrayVec;
 use euclid::{Point2D, Rect, Vector3D};
 use lyon_path::PathEvent;
 use std::mem;
@@ -92,7 +95,7 @@ impl<'a> RectClipper<'a> {
     }
 }
 
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
 enum Edge {
     Left(f32),
     Top(f32),
@@ -103,13 +106,31 @@ enum Edge {
 impl Edge {
     fn point_is_inside(&self, point: &Point2DF32) -> bool {
         match *self {
-            Edge::Left(x_edge) => point.x() >= x_edge,
-            Edge::Top(y_edge) => point.y() >= y_edge,
-            Edge::Right(x_edge) => point.x() <= x_edge,
-            Edge::Bottom(y_edge) => point.y() <= y_edge,
+            Edge::Left(x_edge) => point.x() > x_edge,
+            Edge::Top(y_edge) => point.y() > y_edge,
+            Edge::Right(x_edge) => point.x() < x_edge,
+            Edge::Bottom(y_edge) => point.y() < y_edge,
         }
     }
 
+    fn trivially_test_segment(&self, segment: &Segment) -> EdgeRelativeLocation {
+        let from_inside = self.point_is_inside(&segment.baseline.from());
+        if from_inside != self.point_is_inside(&segment.baseline.to()) {
+            return EdgeRelativeLocation::Intersecting;
+        }
+        if !segment.is_line() {
+            if from_inside != self.point_is_inside(&segment.ctrl.from()) {
+                return EdgeRelativeLocation::Intersecting;
+            }
+            if !segment.is_quadratic() {
+                if from_inside != self.point_is_inside(&segment.ctrl.to()) {
+                    return EdgeRelativeLocation::Intersecting;
+                }
+            }
+        }
+        if from_inside { EdgeRelativeLocation::Inside } else { EdgeRelativeLocation::Outside }
+    }
+
     fn line_intersection(&self, line_segment: &LineSegmentF32) -> Point2DF32 {
         match *self {
             Edge::Left(x_edge) | Edge::Right(x_edge) => {
@@ -120,6 +141,105 @@ impl Edge {
             }
         }
     }
+
+    fn split_segment(&self, segment: &Segment) -> Option<(Segment, Segment)> {
+        if segment.is_line() {
+            return self.split_line_segment(segment);
+        }
+
+        let mut segment = *segment;
+        if segment.is_quadratic() {
+            segment = segment.to_cubic();
+        }
+
+        self.intersect_cubic_segment(&segment, 0.0, 1.0).map(|t| {
+            self.fixup_clipped_segments(&segment.as_cubic_segment().split(t))
+        })
+    }
+
+    fn split_line_segment(&self, segment: &Segment) -> Option<(Segment, Segment)> {
+        let intersection;
+        match *self {
+            Edge::Left(x_edge) | Edge::Right(x_edge) => {
+                if (segment.baseline.from_x() <= x_edge && segment.baseline.to_x() <= x_edge) ||
+                        (segment.baseline.from_x() >= x_edge &&
+                         segment.baseline.to_x() >= x_edge) {
+                    return None
+                }
+                intersection = Point2DF32::new(x_edge, segment.baseline.solve_y_for_x(x_edge));
+            }
+            Edge::Top(y_edge) | Edge::Bottom(y_edge) => {
+                if (segment.baseline.from_y() <= y_edge && segment.baseline.to_y() <= y_edge) ||
+                        (segment.baseline.from_y() >= y_edge &&
+                         segment.baseline.to_y() >= y_edge) {
+                    return None
+                }
+                intersection = Point2DF32::new(segment.baseline.solve_x_for_y(y_edge), y_edge);
+            }
+        };
+        Some((Segment::line(&LineSegmentF32::new(&segment.baseline.from(), &intersection)),
+              Segment::line(&LineSegmentF32::new(&intersection, &segment.baseline.to()))))
+    }
+
+    fn intersect_cubic_segment(&self, segment: &Segment, t_min: f32, t_max: f32) -> Option<f32> {
+        /*
+        println!("... intersect_cubic_segment({:?}, {:?}, t=({}, {}))",
+                 self, segment, t_min, t_max);
+        */
+        let t_mid = lerp(t_min, t_max, 0.5);
+        if t_max - t_min < 0.001 {
+            return Some(t_mid);
+        }
+
+        let (prev_segment, next_segment) = segment.as_cubic_segment().split(t_mid);
+
+        let prev_cubic_segment = prev_segment.as_cubic_segment();
+        let next_cubic_segment = next_segment.as_cubic_segment();
+
+        let (prev_min, prev_max, next_min, next_max, edge);
+        match *self {
+            Edge::Left(x) | Edge::Right(x) => {
+                prev_min = prev_cubic_segment.min_x();
+                prev_max = prev_cubic_segment.max_x();
+                next_min = next_cubic_segment.min_x();
+                next_max = next_cubic_segment.max_x();
+                edge = x;
+            }
+            Edge::Top(y) | Edge::Bottom(y) => {
+                prev_min = prev_cubic_segment.min_y();
+                prev_max = prev_cubic_segment.max_y();
+                next_min = next_cubic_segment.min_y();
+                next_max = next_cubic_segment.max_y();
+                edge = y;
+            }
+        }
+
+        if prev_min < edge && edge < prev_max {
+            self.intersect_cubic_segment(segment, t_min, t_mid)
+        } else if next_min < edge && edge < next_max {
+            self.intersect_cubic_segment(segment, t_mid, t_max)
+        } else if (prev_max == edge && next_min == edge) ||
+                (prev_min == edge && next_max == edge) {
+            Some(t_mid)
+        } else {
+            None
+        }
+    }
+
+    fn fixup_clipped_segments(&self, segment: &(Segment, Segment)) -> (Segment, Segment) {
+        let (mut before, mut after) = *segment;
+        match *self {
+            Edge::Left(x) | Edge::Right(x) => {
+                before.baseline.set_to_x(x);
+                after.baseline.set_from_x(x);
+            }
+            Edge::Top(y) | Edge::Bottom(y) => {
+                before.baseline.set_to_y(y);
+                after.baseline.set_from_y(y);
+            }
+        }
+        (before, after)
+    }
 }
 
 pub(crate) struct ContourRectClipper {
@@ -146,27 +266,78 @@ impl ContourRectClipper {
     }
 
     fn clip_against(&mut self, edge: Edge) {
-        let mut first_point = false;
         let input = mem::replace(&mut self.contour, Contour::new());
-        for event in input.iter() {
-            let (from, to) = (event.baseline.from(), event.baseline.to());
-            if edge.point_is_inside(&to) {
-                if !edge.point_is_inside(&from) {
-                    //println!("clip: {:?} {:?}", from, to);
-                    let intersection = edge.line_intersection(&LineSegmentF32::new(&from, &to));
-                    add_line(&intersection, &mut self.contour, &mut first_point);
+        for mut segment in input.iter() {
+            // Easy cases.
+            match edge.trivially_test_segment(&segment) {
+                EdgeRelativeLocation::Outside => continue,
+                EdgeRelativeLocation::Inside => {
+                    //println!("trivial test inside, pushing segment");
+                    push_segment(&mut self.contour, &segment, edge);
+                    continue;
                 }
-                add_line(&to, &mut self.contour, &mut first_point);
-            } else if edge.point_is_inside(&from) {
-                //println!("clip: {:?} {:?}", from, to);
-                let intersection = edge.line_intersection(&LineSegmentF32::new(&from, &to));
-                add_line(&intersection, &mut self.contour, &mut first_point);
+                EdgeRelativeLocation::Intersecting => {}
+            }
+
+            // We have a potential intersection.
+            //println!("potential intersection: {:?} edge: {:?}", segment, edge);
+            let mut starts_inside = edge.point_is_inside(&segment.baseline.from());
+            while let Some((before_split, after_split)) = edge.split_segment(&segment) {
+                // Push the split segment if appropriate.
+                /*
+                println!("... ... before_split={:?} after_split={:?} starts_inside={:?}",
+                         before_split,
+                         after_split,
+                         starts_inside);
+                  */
+                if starts_inside {
+                    //println!("... split segment case, pushing segment");
+                    push_segment(&mut self.contour, &before_split, edge);
+                }
+
+                // We've now transitioned from inside to outside or vice versa.
+                starts_inside = !starts_inside;
+                segment = after_split;
+            }
+
+            // No more intersections. Push the last segment if applicable.
+            if starts_inside {
+                //println!("... last segment case, pushing segment");
+                push_segment(&mut self.contour, &segment, edge);
             }
         }
 
-        fn add_line(to: &Point2DF32, output: &mut Contour, first_point: &mut bool) {
-            output.push_point(*to, PointFlags::empty());
-            *first_point = false;
+        fn push_segment(contour: &mut Contour, segment: &Segment, edge: Edge) {
+            //println!("... push_segment({:?}, edge={:?}", segment, edge);
+            if let Some(last_position) = contour.last_position() {
+                if last_position != segment.baseline.from() {
+                    // Add a line to join up segments.
+                    //check_point(&segment.baseline.from(), edge);
+                    contour.push_point(segment.baseline.from(), PointFlags::empty());
+                }
+            }
+
+            //check_point(&segment.baseline.to(), edge);
+            contour.push_segment(*segment);
         }
+
+        /*
+        fn check_point(point: &Point2DF32, edge: Edge) {
+            match edge {
+                Edge::Left(x) if point.x() + 0.1 >= x => return,
+                Edge::Top(y) if point.y() + 0.1 >= y => return,
+                Edge::Right(x) if point.x() - 0.1 <= x => return,
+                Edge::Bottom(y) if point.y() - 0.1 <= y => return,
+                _ => {}
+            }
+            panic!("point {:?} outside edge {:?}", point, edge);
+        }
+        */
     }
 }
+
+enum EdgeRelativeLocation {
+    Intersecting,
+    Inside,
+    Outside,
+}

geometry/src/line_segment.rs

@@ -66,6 +66,26 @@ impl LineSegmentF32 {
         self.0[3]
     }
 
+    #[inline]
+    pub fn set_from_x(&mut self, x: f32) {
+        self.0[0] = x
+    }
+
+    #[inline]
+    pub fn set_from_y(&mut self, y: f32) {
+        self.0[1] = y
+    }
+
+    #[inline]
+    pub fn set_to_x(&mut self, x: f32) {
+        self.0[2] = x
+    }
+
+    #[inline]
+    pub fn set_to_y(&mut self, y: f32) {
+        self.0[3] = y
+    }
+
     #[inline]
     pub fn scale(&self, factor: f32) -> LineSegmentF32 {
         LineSegmentF32(self.0 * F32x4::splat(factor))
@@ -176,6 +196,13 @@ impl LineSegmentF32 {
             self.reversed()
         }
     }
+
+    // TODO(pcwalton): Optimize with SIMD.
+    #[inline]
+    pub fn square_length(&self) -> f32 {
+        let (dx, dy) = (self.to_x() - self.from_x(), self.to_y() - self.from_y());
+        dx * dx + dy * dy
+    }
 }
 
 impl Sub<Point2DF32> for LineSegmentF32 {

geometry/src/outline.rs

@@ -29,9 +29,9 @@ pub struct Outline {
 
 #[derive(Clone)]
 pub struct Contour {
-    points: Vec<Point2DF32>,
-    flags: Vec<PointFlags>,
-    bounds: Rect<f32>,
+    pub(crate) points: Vec<Point2DF32>,
+    pub(crate) flags: Vec<PointFlags>,
+    pub(crate) bounds: Rect<f32>,
 }
 
 bitflags! {
@@ -164,6 +164,11 @@ impl Contour {
         self.points[index as usize]
     }
 
+    #[inline]
+    pub(crate) fn last_position(&self) -> Option<Point2DF32> {
+        self.points.last().cloned()
+    }
+
     // TODO(pcwalton): SIMD.
     #[inline]
     pub(crate) fn push_point(&mut self, point: Point2DF32, flags: PointFlags) {

geometry/src/segment.rs

@@ -239,6 +239,13 @@ impl<'s> CubicSegment<'s> {
                                   self.0.ctrl.from_y(),
                                   self.0.ctrl.to_y(),
                                   self.0.baseline.to_y());
+
+        // TODO(pcwalton): Optimize this.
+        if p0p1p2p3[0] <= p0p1p2p3[1] && p0p1p2p3[0] <= p0p1p2p3[2] &&
+                p0p1p2p3[1] <= p0p1p2p3[3] && p0p1p2p3[2] <= p0p1p2p3[3] {
+            return (None, None);
+        }
+
         let pxp0p1p2 = p0p1p2p3.wxyz();
         let pxv0v1v2 = p0p1p2p3 - pxp0p1p2;
         let (v0, v1, v2) = (pxv0v1v2[1], pxv0v1v2[2], pxv0v1v2[3]);
@@ -262,6 +269,15 @@ impl<'s> CubicSegment<'s> {
 
         const EPSILON: f32 = 0.001;
     }
+
+    #[inline]
+    pub fn min_x(&self) -> f32 { f32::min(self.0.baseline.min_x(), self.0.ctrl.min_x()) }
+    #[inline]
+    pub fn min_y(&self) -> f32 { f32::min(self.0.baseline.min_y(), self.0.ctrl.min_y()) }
+    #[inline]
+    pub fn max_x(&self) -> f32 { f32::max(self.0.baseline.max_x(), self.0.ctrl.max_x()) }
+    #[inline]
+    pub fn max_y(&self) -> f32 { f32::max(self.0.baseline.max_y(), self.0.ctrl.max_y()) }
 }
 
 // Lyon interoperability

renderer/src/gpu_data.rs

@@ -197,13 +197,11 @@ impl BuiltObject {
 
     // TODO(pcwalton): Optimize this better with SIMD!
     pub fn generate_fill_primitives_for_line(&mut self, mut segment: LineSegmentF32, tile_y: i16) {
-        /*
-        println!("... generate_fill_primitives_for_line(): segment={:?} tile_y={} ({}-{})",
+        /*println!("... generate_fill_primitives_for_line(): segment={:?} tile_y={} ({}-{})",
                     segment,
                     tile_y,
                     tile_y as f32 * TILE_HEIGHT as f32,
-                    (tile_y + 1) as f32 * TILE_HEIGHT as f32);
-        */
+                    (tile_y + 1) as f32 * TILE_HEIGHT as f32);*/
 
         let winding = segment.from_x() > segment.to_x();
         let (segment_left, segment_right) = if !winding {

renderer/src/tiles.rs

@@ -449,6 +449,8 @@ impl ActiveEdge {
         tile_y: i16,
     ) -> Option<LineSegmentF32> {
         let tile_bottom = ((i32::from(tile_y) + 1) * TILE_HEIGHT as i32) as f32;
+        /*println!("process_line_segment({:?}, tile_y={}) tile_bottom={}",
+                 line_segment, tile_y, tile_bottom);*/
         if line_segment.max_y() <= tile_bottom {
             built_object.generate_fill_primitives_for_line(*line_segment, tile_y);
             return None;