Switch to guard-band style clipping to eliminate artefacts

geometry/src/outline.rs

@@ -422,12 +422,8 @@ impl Contour {
     fn prepare_for_tiling(&mut self, view_box: RectF32) {
         // Snap points to the view box bounds. This mops up floating point error from the clipping
         // process.
-        let (origin_upper_left, origin_lower_right) = (view_box.origin(), view_box.lower_right());
         let (mut last_endpoint_index, mut contour_is_monotonic) = (None, true);
         for point_index in 0..(self.points.len() as u32) {
-            let position = &mut self.points[point_index as usize];
-            *position = position.clamp(origin_upper_left, origin_lower_right);
-
             if contour_is_monotonic {
                 if self.point_is_endpoint(point_index) {
                     if let Some(last_endpoint_index) = last_endpoint_index {

renderer/src/builder.rs

@@ -98,8 +98,8 @@ impl SceneBuilder {
 
             // Remap and copy fills, culling as necessary.
             for fill in &object.fills {
-                let object_tile_index = object.tile_coords_to_index(fill.tile_x as i32,
-                                                                    fill.tile_y as i32);
+                let object_tile_index =
+                    object.tile_coords_to_index(fill.tile_x as i32, fill.tile_y as i32).unwrap();
                 let mask_tile_index =
                     object_tile_index_to_batch_mask_tile_index[object_tile_index as usize];
                 if mask_tile_index < u16::MAX {

renderer/src/gpu_data.rs

@@ -109,27 +109,22 @@ impl BuiltObject {
     // TODO(pcwalton): SIMD-ify `tile_x` and `tile_y`.
     fn add_fill(&mut self, segment: &LineSegmentF32, tile_x: i32, tile_y: i32) {
         //println!("add_fill({:?} ({}, {}))", segment, tile_x, tile_y);
+        let tile_index = match self.tile_coords_to_index(tile_x, tile_y) {
+            None => return,
+            Some(tile_index) => tile_index,
+        };
 
-        let mut segment = (segment.0 * F32x4::splat(256.0)).to_i32x4();
+        debug_assert_eq!(TILE_WIDTH, TILE_HEIGHT);
+        let tile_size = F32x4::splat(TILE_WIDTH as f32);
+        let (min, max) = (F32x4::default(), F32x4::splat((TILE_WIDTH * 256 - 1) as f32));
+        let shuffle_mask = I32x4::new(0x0c08_0400, 0x0d05_0901, 0, 0).as_u8x16();
 
-        let tile_origin_x = (TILE_WIDTH as i32) * 256 * tile_x;
-        let tile_origin_y = (TILE_HEIGHT as i32) * 256 * tile_y;
-        let tile_origin = I32x4::new(tile_origin_x, tile_origin_y, tile_origin_x, tile_origin_y);
+        let tile_upper_left =
+            F32x4::new(tile_x as f32, tile_y as f32, tile_x as f32, tile_y as f32) * tile_size;
 
-        segment = segment - tile_origin;
-        /*
-        println!("... before min: {} {} {} {}",
-                    segment[0], segment[1], segment[2], segment[3]);
-        */
-        //segment = Sse41::max_epi32(segment, Sse41::setzero_epi32());
-        segment = segment.min(I32x4::splat(0x0fff));
-        //println!("... after min: {} {} {} {}", segment[0], segment[1], segment[2], segment[3]);
-
-        let shuffle_mask = I32x4::new(0x0c08_0400, 0x0d05_0901, 0, 0);
-        segment = segment
-            .as_u8x16()
-            .shuffle(shuffle_mask.as_u8x16())
-            .as_i32x4();
+        let segment = (segment.0 - tile_upper_left) * F32x4::splat(256.0);
+        let segment =
+            segment.clamp(min, max).to_i32x4().as_u8x16().shuffle(shuffle_mask).as_i32x4();
 
         // Unpack whole and fractional pixels.
         let px = LineSegmentU4((segment[1] | (segment[1] >> 12)) as u16);
@@ -142,8 +137,6 @@ impl BuiltObject {
             return;
         }
 
-        let tile_index = self.tile_coords_to_index(tile_x, tile_y);
-
         //println!("... ... OK, pushing");
 
         self.fills.push(FillObjectPrimitive {
@@ -233,18 +226,26 @@ impl BuiltObject {
     }
 
     // FIXME(pcwalton): Use a `Point2DI32` instead?
-    pub fn tile_coords_to_index(&self, tile_x: i32, tile_y: i32) -> u32 {
+    pub fn tile_coords_to_index(&self, tile_x: i32, tile_y: i32) -> Option<u32> {
         /*println!("tile_coords_to_index(x={}, y={}, tile_rect={:?})",
         tile_x,
         tile_y,
         self.tile_rect);*/
-        (tile_y - self.tile_rect.min_y()) as u32 * self.tile_rect.size().x() as u32
-            + (tile_x - self.tile_rect.min_x()) as u32
+        if tile_x < self.tile_rect.min_x() || tile_x >= self.tile_rect.max_x() ||
+                tile_y < self.tile_rect.min_y() || tile_y >= self.tile_rect.max_y() {
+            None
+        } else {
+            Some((tile_y - self.tile_rect.min_y()) as u32 * self.tile_rect.size().x() as u32
+                + (tile_x - self.tile_rect.min_x()) as u32)
+        }
     }
 
-    pub fn get_tile_mut(&mut self, tile_x: i32, tile_y: i32) -> &mut TileObjectPrimitive {
+    pub fn get_tile_mut(&mut self, tile_x: i32, tile_y: i32) -> Option<&mut TileObjectPrimitive> {
         let tile_index = self.tile_coords_to_index(tile_x, tile_y);
-        &mut self.tiles[tile_index as usize]
+        match tile_index {
+            None => None,
+            Some(tile_index) => Some(&mut self.tiles[tile_index as usize]),
+        }
     }
 }
 

renderer/src/tiles.rs

@@ -169,16 +169,17 @@ impl<'o, 'z> Tiler<'o, 'z> {
             // Move over to the correct tile, filling in as we go.
             while current_tile_x < segment_tile_x {
                 //println!("... emitting backdrop {} @ tile {}", current_winding, current_tile_x);
-                self.built_object
-                    .get_tile_mut(current_tile_x, tile_y)
-                    .backdrop = current_winding;
+                if let Some(tile) = self.built_object.get_tile_mut(current_tile_x, tile_y) {
+                    tile.backdrop = current_winding;
+                }
+
                 current_tile_x += 1;
                 current_subtile_x = 0.0;
             }
 
             // Do final subtile fill, if necessary.
             debug_assert_eq!(current_tile_x, segment_tile_x);
-            debug_assert!(current_tile_x <= self.built_object.tile_rect.max_x());
+            //debug_assert!(current_tile_x <= self.built_object.tile_rect.max_x());
             let segment_subtile_x =
                 segment_x - (i32::from(current_tile_x) * TILE_WIDTH as i32) as f32;
             if segment_subtile_x > current_subtile_x {

simd/src/x86.rs

@@ -47,6 +47,11 @@ impl F32x4 {
         unsafe { F32x4(x86_64::_mm_max_ps(self.0, other.0)) }
     }
 
+    #[inline]
+    pub fn clamp(self, min: F32x4, max: F32x4) -> F32x4 {
+        self.max(min).min(max)
+    }
+
     #[inline]
     pub fn abs(self) -> F32x4 {
         unsafe {