Bug 1574493 - Part 2. Remove snapping in frame building. r=kvark

This will be rewritten in a later patch in the series. The shaders will
be provided the correct information and will no longer need to concern
themselves with snapping.

Differential Revision: https://phabricator.services.mozilla.com/D45057

--HG--
extra : moz-landing-system : lando

gfx/wr/webrender/res/brush.glsl

@@ -70,9 +70,7 @@ void main(void) {
             ph.local_clip_rect,
             ph.z,
             transform,
-            pic_task,
+            pic_task
-            ph.local_rect,
-            ph.snap_offsets
         );
 
         // TODO(gw): transform bounds may be referenced by

gfx/wr/webrender/res/clip_shared.glsl

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include rect,render_task,gpu_cache,snap,transform
+#include rect,render_task,gpu_cache,transform
 
 #ifdef WR_VERTEX_SHADER
 
@@ -11,7 +11,6 @@ in ivec4 aClipDataResourceAddress;
 in vec2 aClipLocalPos;
 in vec4 aClipTileRect;
 in vec4 aClipDeviceArea;
-in vec4 aClipSnapOffsets;
 in vec4 aClipOrigins;
 in float aDevicePixelScale;
 
@@ -23,7 +22,6 @@ struct ClipMaskInstance {
     vec2 local_pos;
     RectWithSize tile_rect;
     RectWithSize sub_rect;
-    vec4 snap_offsets;
     vec2 task_origin;
     vec2 screen_origin;
     float device_pixel_scale;
@@ -39,7 +37,6 @@ ClipMaskInstance fetch_clip_item() {
     cmi.local_pos = aClipLocalPos;
     cmi.tile_rect = RectWithSize(aClipTileRect.xy, aClipTileRect.zw);
     cmi.sub_rect = RectWithSize(aClipDeviceArea.xy, aClipDeviceArea.zw);
-    cmi.snap_offsets = aClipSnapOffsets;
     cmi.task_origin = aClipOrigins.xy;
     cmi.screen_origin = aClipOrigins.zw;
     cmi.device_pixel_scale = aDevicePixelScale;
@@ -64,23 +61,10 @@ ClipVertexInfo write_clip_tile_vertex(RectWithSize local_clip_rect,
                                       Transform prim_transform,
                                       Transform clip_transform,
                                       RectWithSize sub_rect,
-                                      vec4 snap_offsets,
                                       vec2 task_origin,
                                       vec2 screen_origin,
                                       float device_pixel_scale) {
     vec2 device_pos = screen_origin + sub_rect.p0 + aPosition.xy * sub_rect.size;
-
-    // If the primitive we are drawing a clip mask for was snapped, then
-    // remove the effect of that snapping, so that the local position
-    // interpolation below works correctly relative to the clip item.
-    vec2 snap_offset = mix(
-        snap_offsets.xy,
-        snap_offsets.zw,
-        aPosition.xy
-    );
-
-    device_pos -= snap_offset;
-
     vec2 world_pos = device_pos / device_pixel_scale;
 
     vec4 pos = prim_transform.m * vec4(world_pos, 0.0, 1.0);

gfx/wr/webrender/res/cs_clip_box_shadow.glsl

@@ -52,7 +52,6 @@ void main(void) {
         prim_transform,
         clip_transform,
         cmi.sub_rect,
-        cmi.snap_offsets,
         cmi.task_origin,
         cmi.screen_origin,
         cmi.device_pixel_scale

gfx/wr/webrender/res/cs_clip_image.glsl

@@ -35,7 +35,6 @@ void main(void) {
         prim_transform,
         clip_transform,
         cmi.sub_rect,
-        cmi.snap_offsets,
         cmi.task_origin,
         cmi.screen_origin,
         cmi.device_pixel_scale

gfx/wr/webrender/res/cs_clip_rectangle.glsl

@@ -77,7 +77,6 @@ void main(void) {
         prim_transform,
         clip_transform,
         cmi.sub_rect,
-        cmi.snap_offsets,
         cmi.task_origin,
         cmi.screen_origin,
         cmi.device_pixel_scale

gfx/wr/webrender/res/prim_shared.glsl

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include rect,render_task,gpu_cache,snap,transform
+#include rect,render_task,gpu_cache,transform
 
 #define EXTEND_MODE_CLAMP  0
 #define EXTEND_MODE_REPEAT 1
@@ -47,13 +47,12 @@ uniform HIGHP_SAMPLER_FLOAT isampler2D sPrimitiveHeadersI;
 // Instanced attributes
 in ivec4 aData;
 
-#define VECS_PER_PRIM_HEADER_F 3U
+#define VECS_PER_PRIM_HEADER_F 2U
 #define VECS_PER_PRIM_HEADER_I 2U
 
 struct PrimitiveHeader {
     RectWithSize local_rect;
     RectWithSize local_clip_rect;
-    vec4 snap_offsets;
     float z;
     int specific_prim_address;
     int transform_id;
@@ -66,7 +65,6 @@ PrimitiveHeader fetch_prim_header(int index) {
     ivec2 uv_f = get_fetch_uv(index, VECS_PER_PRIM_HEADER_F);
     vec4 local_rect = TEXEL_FETCH(sPrimitiveHeadersF, uv_f, 0, ivec2(0, 0));
     vec4 local_clip_rect = TEXEL_FETCH(sPrimitiveHeadersF, uv_f, 0, ivec2(1, 0));
-    ph.snap_offsets = TEXEL_FETCH(sPrimitiveHeadersF, uv_f, 0, ivec2(2, 0));
     ph.local_rect = RectWithSize(local_rect.xy, local_rect.zw);
     ph.local_clip_rect = RectWithSize(local_clip_rect.xy, local_clip_rect.zw);
 
@@ -91,9 +89,7 @@ VertexInfo write_vertex(RectWithSize instance_rect,
                         RectWithSize local_clip_rect,
                         float z,
                         Transform transform,
-                        PictureTask task,
+                        PictureTask task) {
-                        RectWithSize snap_rect,
-                        vec4 snap_offsets) {
 
     // Select the corner of the local rect that we are processing.
     vec2 local_pos = instance_rect.p0 + instance_rect.size * aPosition.xy;
@@ -101,13 +97,6 @@ VertexInfo write_vertex(RectWithSize instance_rect,
     // Clamp to the two local clip rects.
     vec2 clamped_local_pos = clamp_rect(local_pos, local_clip_rect);
 
-    /// Compute the snapping offset.
-    vec2 snap_offset = compute_snap_offset(
-        clamped_local_pos,
-        snap_rect,
-        snap_offsets
-    );
-
     // Transform the current vertex to world space.
     vec4 world_pos = transform.m * vec4(clamped_local_pos, 0.0, 1.0);
 
@@ -115,13 +104,13 @@ VertexInfo write_vertex(RectWithSize instance_rect,
     vec2 device_pos = world_pos.xy * task.device_pixel_scale;
 
     // Apply offsets for the render task to get correct screen location.
-    vec2 final_offset = snap_offset - task.content_origin + task.common_data.task_rect.p0;
+    vec2 final_offset = -task.content_origin + task.common_data.task_rect.p0;
 
     gl_Position = uTransform * vec4(device_pos + final_offset * world_pos.w, z * world_pos.w, world_pos.w);
 
     VertexInfo vi = VertexInfo(
         clamped_local_pos,
-        snap_offset,
+        vec2(0.0, 0.0),
         world_pos
     );
 

gfx/wr/webrender/res/snap.glsl

@@ -1,22 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifdef WR_VERTEX_SHADER
-
-/// Given a point within a local rectangle, and the device space corners
-/// offsets for the unsnapped primitive, return the snap offsets. This *must*
-/// exactly match the logic in the Rust compute_snap_offset_impl function.
-vec2 compute_snap_offset(
-    vec2 reference_pos,
-    RectWithSize reference_rect,
-    vec4 snap_positions
-) {
-    /// Compute the position of this vertex inside the snap rectangle.
-    vec2 normalized_snap_pos = (reference_pos - reference_rect.p0) / reference_rect.size;
-
-    /// Compute the actual world offset for this vertex needed to make it snap.
-    return mix(snap_positions.xy, snap_positions.zw, normalized_snap_pos);
-}
-
-#endif //WR_VERTEX_SHADER

gfx/wr/webrender/src/batch.rs

@@ -10,7 +10,7 @@ use crate::clip_scroll_tree::{ClipScrollTree, ROOT_SPATIAL_NODE_INDEX, SpatialNo
 use crate::glyph_rasterizer::GlyphFormat;
 use crate::gpu_cache::{GpuBlockData, GpuCache, GpuCacheHandle, GpuCacheAddress};
 use crate::gpu_types::{BrushFlags, BrushInstance, PrimitiveHeaders, ZBufferId, ZBufferIdGenerator};
-use crate::gpu_types::{ClipMaskInstance, SplitCompositeInstance, SnapOffsets};
+use crate::gpu_types::{ClipMaskInstance, SplitCompositeInstance};
 use crate::gpu_types::{PrimitiveInstanceData, RasterizationSpace, GlyphInstance};
 use crate::gpu_types::{PrimitiveHeader, PrimitiveHeaderIndex, TransformPaletteId, TransformPalette};
 use crate::internal_types::{FastHashMap, SavedTargetIndex, Swizzle, TextureSource, Filter};
@@ -18,7 +18,6 @@ use crate::picture::{Picture3DContext, PictureCompositeMode, PicturePrimitive, T
 use crate::prim_store::{DeferredResolve, EdgeAaSegmentMask, PrimitiveInstanceKind, PrimitiveVisibilityIndex, PrimitiveVisibilityMask};
 use crate::prim_store::{VisibleGradientTile, PrimitiveInstance, PrimitiveOpacity, SegmentInstanceIndex};
 use crate::prim_store::{BrushSegment, ClipMaskKind, ClipTaskIndex, VECS_PER_SEGMENT};
-use crate::prim_store::{recompute_snap_offsets};
 use crate::prim_store::image::ImageSource;
 use crate::render_backend::DataStores;
 use crate::render_target::RenderTargetContext;
@@ -708,7 +707,7 @@ impl BatchBuilder {
         let prim_common_data = &ctx.data_stores.as_common_data(&prim_instance);
         let prim_rect = LayoutRect::new(
             prim_instance.prim_origin,
-            prim_common_data.prim_size,
+            prim_common_data.prim_size
         );
 
         let mut batch_features = BatchFeatures::empty();
@@ -720,7 +719,6 @@ impl BatchBuilder {
             batch_features |= BatchFeatures::ANTIALIASING;
         }
 
-        let snap_offsets = prim_info.snap_offsets;
         let prim_vis_mask = prim_info.visibility_mask;
         let clip_task_address = ctx.get_prim_clip_task_address(
             prim_info.clip_task_index,
@@ -751,7 +749,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -818,7 +815,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -870,7 +866,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -1040,7 +1035,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -1077,9 +1071,8 @@ impl BatchBuilder {
                 let prim_cache_address = gpu_cache.get_address(&ctx.globals.default_image_handle);
 
                 let prim_header = PrimitiveHeader {
-                    local_rect: picture.snapped_local_rect,
+                    local_rect: picture.local_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -1104,9 +1097,8 @@ impl BatchBuilder {
                             );
 
                             let prim_header = PrimitiveHeader {
-                                local_rect: pic.snapped_local_rect,
+                                local_rect: pic.local_rect,
                                 local_clip_rect: child_prim_info.combined_local_clip_rect,
-                                snap_offsets,
                                 specific_prim_address: GpuCacheAddress::INVALID,
                                 transform_id: transforms
                                     .get_id(
@@ -1225,7 +1217,6 @@ impl BatchBuilder {
                                         let prim_header = PrimitiveHeader {
                                             local_rect: local_tile_rect,
                                             local_clip_rect: local_tile_clip_rect,
-                                            snap_offsets: SnapOffsets::empty(),
                                             specific_prim_address: prim_cache_address,
                                             transform_id,
                                         };
@@ -1295,7 +1286,6 @@ impl BatchBuilder {
                                         let prim_header = PrimitiveHeader {
                                             local_rect: local_tile_rect,
                                             local_clip_rect: local_tile_clip_rect,
-                                            snap_offsets: SnapOffsets::empty(),
                                             specific_prim_address: prim_cache_address,
                                             transform_id,
                                         };
@@ -1412,7 +1402,6 @@ impl BatchBuilder {
 
                                             let shadow_prim_header = PrimitiveHeader {
                                                 local_rect: shadow_rect,
-                                                snap_offsets: prim_info.shadow_snap_offsets,
                                                 specific_prim_address: shadow_prim_address,
                                                 ..prim_header
                                             };
@@ -1705,9 +1694,8 @@ impl BatchBuilder {
                                 };
 
                                 let prim_header = PrimitiveHeader {
-                                    local_rect: picture.snapped_local_rect,
+                                    local_rect: picture.local_rect,
                                     local_clip_rect: prim_info.combined_local_clip_rect,
-                                    snap_offsets,
                                     specific_prim_address: prim_cache_address,
                                     transform_id,
                                 };
@@ -1828,7 +1816,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -1903,7 +1890,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -2013,7 +1999,6 @@ impl BatchBuilder {
                 let prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: prim_cache_address,
                     transform_id,
                 };
@@ -2119,7 +2104,6 @@ impl BatchBuilder {
                     let prim_header = PrimitiveHeader {
                         local_rect: prim_rect,
                         local_clip_rect: prim_info.combined_local_clip_rect,
-                        snap_offsets,
                         specific_prim_address: prim_cache_address,
                         transform_id,
                     };
@@ -2168,7 +2152,6 @@ impl BatchBuilder {
                         let prim_header = PrimitiveHeader {
                             local_rect: prim_rect,
                             local_clip_rect: image_instance.tight_local_clip_rect,
-                            snap_offsets,
                             specific_prim_address: gpu_cache.get_address(&gpu_handle),
                             transform_id,
                         };
@@ -2212,7 +2195,6 @@ impl BatchBuilder {
                 let mut prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: GpuCacheAddress::INVALID,
                     transform_id,
                 };
@@ -2340,7 +2322,6 @@ impl BatchBuilder {
                 let mut prim_header = PrimitiveHeader {
                     local_rect: prim_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
-                    snap_offsets,
                     specific_prim_address: GpuCacheAddress::INVALID,
                     transform_id,
                 };
@@ -2444,10 +2425,9 @@ impl BatchBuilder {
                 let prim_cache_address = gpu_cache.get_address(&ctx.globals.default_image_handle);
                 let backdrop_picture = &ctx.prim_store.pictures[backdrop_pic_index.0];
                 let prim_header = PrimitiveHeader {
-                    local_rect: backdrop_picture.snapped_local_rect,
+                    local_rect: backdrop_picture.local_rect,
                     local_clip_rect: prim_info.combined_local_clip_rect,
                     transform_id,
-                    snap_offsets: SnapOffsets::empty(),
                     specific_prim_address: prim_cache_address,
                 };
 
@@ -2668,18 +2648,10 @@ impl BatchBuilder {
         let user_data = [stops_handle.as_int(gpu_cache), 0, 0, 0];
 
         for tile in visible_tiles {
-            // Adjust the snap offsets for the tile.
-            let snap_offsets = recompute_snap_offsets(
-                tile.local_rect,
-                base_prim_header.local_rect,
-                base_prim_header.snap_offsets,
-            );
-
             let prim_header = PrimitiveHeader {
                 specific_prim_address: gpu_cache.get_address(&tile.handle),
                 local_rect: tile.local_rect,
                 local_clip_rect: tile.local_clip_rect,
-                snap_offsets,
                 ..*base_prim_header
             };
             let prim_header_index = prim_headers.push(&prim_header, z_id, user_data);
@@ -2949,7 +2921,6 @@ impl ClipBatcher {
             local_pos,
             tile_rect: LayoutRect::zero(),
             sub_rect,
-            snap_offsets: SnapOffsets::empty(),
             task_origin,
             screen_origin,
             device_pixel_scale,
@@ -3075,7 +3046,6 @@ impl ClipBatcher {
         actual_rect: DeviceIntRect,
         world_rect: &WorldRect,
         device_pixel_scale: DevicePixelScale,
-        snap_offsets: SnapOffsets,
         task_origin: DevicePoint,
         screen_origin: DevicePoint,
     ) {
@@ -3108,7 +3078,6 @@ impl ClipBatcher {
                     DevicePoint::zero(),
                     actual_rect.size.to_f32(),
                 ),
-                snap_offsets,
                 task_origin,
                 screen_origin,
                 device_pixel_scale: device_pixel_scale.0,

gfx/wr/webrender/src/frame_builder.rs

@@ -392,7 +392,7 @@ impl FrameBuilder {
             &frame_context,
             gpu_cache,
             &self.clip_store,
-            &data_stores.clip,
+            data_stores,
         );
 
         {

gfx/wr/webrender/src/gpu_types.rs

@@ -169,7 +169,6 @@ pub struct ClipMaskInstance {
     pub local_pos: LayoutPoint,
     pub tile_rect: LayoutRect,
     pub sub_rect: DeviceRect,
-    pub snap_offsets: SnapOffsets,
     pub task_origin: DevicePoint,
     pub screen_origin: DevicePoint,
     pub device_pixel_scale: f32,
@@ -250,7 +249,6 @@ impl PrimitiveHeaders {
         self.headers_float.push(PrimitiveHeaderF {
             local_rect: prim_header.local_rect,
             local_clip_rect: prim_header.local_clip_rect,
-            snap_offsets: prim_header.snap_offsets,
         });
 
         self.headers_int.push(PrimitiveHeaderI {
@@ -271,7 +269,6 @@ impl PrimitiveHeaders {
 pub struct PrimitiveHeader {
     pub local_rect: LayoutRect,
     pub local_clip_rect: LayoutRect,
-    pub snap_offsets: SnapOffsets,
     pub specific_prim_address: GpuCacheAddress,
     pub transform_id: TransformPaletteId,
 }
@@ -284,7 +281,6 @@ pub struct PrimitiveHeader {
 pub struct PrimitiveHeaderF {
     pub local_rect: LayoutRect,
     pub local_clip_rect: LayoutRect,
-    pub snap_offsets: SnapOffsets,
 }
 
 // i32 parts of a primitive header
@@ -593,33 +589,6 @@ pub enum UvRectKind {
     },
 }
 
-/// Represents offsets in device pixels that a primitive
-/// was snapped to.
-#[cfg_attr(feature = "capture", derive(Serialize))]
-#[cfg_attr(feature = "replay", derive(Deserialize))]
-#[derive(Copy, Clone, Debug)]
-#[repr(C)]
-pub struct SnapOffsets {
-    /// How far the top left corner was snapped
-    pub top_left: DeviceVector2D,
-    /// How far the bottom right corner was snapped
-    pub bottom_right: DeviceVector2D,
-}
-
-impl SnapOffsets {
-    pub fn empty() -> Self {
-        SnapOffsets {
-            top_left: DeviceVector2D::zero(),
-            bottom_right: DeviceVector2D::zero(),
-        }
-    }
-
-    pub fn is_empty(&self) -> bool {
-        let zero = DeviceVector2D::zero();
-        self.top_left == zero && self.bottom_right == zero
-    }
-}
-
 #[derive(Debug, Copy, Clone)]
 #[cfg_attr(feature = "capture", derive(Serialize))]
 #[cfg_attr(feature = "replay", derive(Deserialize))]

gfx/wr/webrender/src/picture.rs

@@ -7,7 +7,7 @@ use api::{PropertyBinding, PropertyBindingId, FilterPrimitive, FontRenderMode};
 use api::{DebugFlags, RasterSpace, ImageKey, ColorF};
 use api::units::*;
 use crate::box_shadow::{BLUR_SAMPLE_SCALE};
-use crate::clip::{ClipStore, ClipDataStore, ClipChainInstance, ClipDataHandle, ClipChainId};
+use crate::clip::{ClipStore, ClipChainInstance, ClipDataHandle, ClipChainId};
 use crate::clip_scroll_tree::{ROOT_SPATIAL_NODE_INDEX,
     ClipScrollTree, CoordinateSpaceMapping, SpatialNodeIndex, VisibleFace, CoordinateSystemId
 };
@@ -1781,7 +1781,7 @@ impl<'a> PictureUpdateState<'a> {
         frame_context: &FrameBuildingContext,
         gpu_cache: &mut GpuCache,
         clip_store: &ClipStore,
-        clip_data_store: &ClipDataStore,
+        data_stores: &mut DataStores,
     ) {
         profile_marker!("UpdatePictures");
 
@@ -1798,7 +1798,7 @@ impl<'a> PictureUpdateState<'a> {
             frame_context,
             gpu_cache,
             clip_store,
-            clip_data_store,
+            data_stores,
         );
 
         if !state.are_raster_roots_assigned {
@@ -1861,7 +1861,7 @@ impl<'a> PictureUpdateState<'a> {
         frame_context: &FrameBuildingContext,
         gpu_cache: &mut GpuCache,
         clip_store: &ClipStore,
-        clip_data_store: &ClipDataStore,
+        data_stores: &mut DataStores,
     ) {
         if let Some(prim_list) = picture_primitives[pic_index.0].pre_update(
             self,
@@ -1874,7 +1874,7 @@ impl<'a> PictureUpdateState<'a> {
                     frame_context,
                     gpu_cache,
                     clip_store,
-                    clip_data_store,
+                    data_stores,
                 );
             }
 
@@ -1882,6 +1882,7 @@ impl<'a> PictureUpdateState<'a> {
                 prim_list,
                 self,
                 frame_context,
+                data_stores,
             );
         }
     }
@@ -2196,6 +2197,10 @@ pub struct PrimitiveClusterIndex(pub u32);
 #[cfg_attr(feature = "capture", derive(Serialize))]
 pub struct ClusterIndex(pub u16);
 
+#[derive(Debug, Copy, Clone)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+pub struct PrimitiveIndex(pub u32);
+
 impl ClusterIndex {
     pub const INVALID: ClusterIndex = ClusterIndex(u16::MAX);
 }
@@ -2217,6 +2222,10 @@ pub struct PrimitiveList {
     pub pictures: PictureList,
     /// List of primitives grouped into clusters.
     pub clusters: SmallVec<[PrimitiveCluster; 4]>,
+    /// List of primitive indicies that can only update
+    /// the cluster during frame building. This maps to
+    /// primitives in the prim_instances array.
+    pub deferred_prims: Vec<PrimitiveIndex>,
 }
 
 impl PrimitiveList {
@@ -2229,6 +2238,7 @@ impl PrimitiveList {
             prim_instances: Vec::new(),
             pictures: SmallVec::new(),
             clusters: SmallVec::new(),
+            deferred_prims: Vec::new(),
         }
     }
 
@@ -2243,10 +2253,11 @@ impl PrimitiveList {
         let mut pictures = SmallVec::new();
         let mut clusters_map = FastHashMap::default();
         let mut clusters: SmallVec<[PrimitiveCluster; 4]> = SmallVec::new();
+        let mut deferred_prims = Vec::new();
 
         // Walk the list of primitive instances and extract any that
         // are pictures.
-        for prim_instance in &mut prim_instances {
+        for (prim_index, prim_instance) in &mut prim_instances.iter_mut().enumerate() {
             // Check if this primitive is a picture. In future we should
             // remove this match and embed this info directly in the primitive instance.
             let is_pic = match prim_instance.kind {
@@ -2302,8 +2313,12 @@ impl PrimitiveList {
                     (data.is_backface_visible, data.prim_size)
                 }
                 PrimitiveInstanceKind::Backdrop { data_handle, .. } => {
+                    // We don't know the actual size of the backdrop until frame
+                    // building, so use an empty rect for now and add it to the
+                    // deferred primitive list.
                     let data = &interners.backdrop[data_handle];
-                    (data.is_backface_visible, data.prim_size)
+                    deferred_prims.push(PrimitiveIndex(prim_index as u32));
+                    (data.is_backface_visible, LayoutSize::zero())
                 }
                 PrimitiveInstanceKind::PushClipChain |
                 PrimitiveInstanceKind::PopClipChain => {
@@ -2358,6 +2373,7 @@ impl PrimitiveList {
             prim_instances,
             pictures,
             clusters,
+            deferred_prims,
         }
     }
 }
@@ -2423,17 +2439,10 @@ pub struct PicturePrimitive {
     /// composited into the parent picture.
     pub spatial_node_index: SpatialNodeIndex,
 
-    /// The local rect of this picture. It is built
-    /// dynamically when updating visibility. It takes
-    /// into account snapping in device space for its
-    /// children.
-    pub snapped_local_rect: LayoutRect,
-
     /// The local rect of this picture. It is built
     /// dynamically during the first picture traversal. It
-    /// does not take into account snapping in device for
+    /// is composed of already snapped primitives.
-    /// its children.
+    pub local_rect: LayoutRect,
-    pub unsnapped_local_rect: LayoutRect,
 
     /// If false, this picture needs to (re)build segments
     /// if it supports segment rendering. This can occur
@@ -2458,8 +2467,7 @@ impl PicturePrimitive {
     ) {
         pt.new_level(format!("{:?}", self_index));
         pt.add_item(format!("prim_count: {:?}", self.prim_list.prim_instances.len()));
-        pt.add_item(format!("snapped_local_rect: {:?}", self.snapped_local_rect));
+        pt.add_item(format!("local_rect: {:?}", self.local_rect));
-        pt.add_item(format!("unsnapped_local_rect: {:?}", self.unsnapped_local_rect));
         pt.add_item(format!("spatial_node_index: {:?}", self.spatial_node_index));
         pt.add_item(format!("raster_config: {:?}", self.raster_config));
         pt.add_item(format!("requested_composite_mode: {:?}", self.requested_composite_mode));
@@ -2568,8 +2576,7 @@ impl PicturePrimitive {
             is_backface_visible,
             requested_raster_space,
             spatial_node_index,
-            snapped_local_rect: LayoutRect::zero(),
+            local_rect: LayoutRect::zero(),
-            unsnapped_local_rect: LayoutRect::zero(),
             tile_cache,
             options,
             segments_are_valid: false,
@@ -2673,7 +2680,7 @@ impl PicturePrimitive {
 
         match self.raster_config {
             Some(ref raster_config) => {
-                let pic_rect = PictureRect::from_untyped(&self.snapped_local_rect.to_untyped());
+                let pic_rect = PictureRect::from_untyped(&self.local_rect.to_untyped());
 
                 let device_pixel_scale = frame_state
                     .surfaces[raster_config.surface_index.0]
@@ -3444,6 +3451,7 @@ impl PicturePrimitive {
         prim_list: PrimitiveList,
         state: &mut PictureUpdateState,
         frame_context: &FrameBuildingContext,
+        data_stores: &mut DataStores,
     ) {
         // Restore the pictures list used during recursion.
         self.prim_list = prim_list;
@@ -3451,6 +3459,59 @@ impl PicturePrimitive {
         // Pop the state information about this picture.
         state.pop_picture();
 
+        // Update any primitives/cluster bounding rects that can only be done
+        // with information available during frame building.
+        for prim_index in &self.prim_list.deferred_prims {
+            let prim_instance = &mut self.prim_list.prim_instances[prim_index.0 as usize];
+            match prim_instance.kind {
+                PrimitiveInstanceKind::Backdrop { data_handle, .. } => {
+                    // The actual size and clip rect of this primitive are determined by computing the bounding
+                    // box of the projected rect of the backdrop-filter element onto the backdrop.
+                    let prim_data = &mut data_stores.backdrop[data_handle];
+                    let spatial_node_index = prim_data.kind.spatial_node_index;
+
+                    // We cannot use the relative transform between the backdrop and the element because
+                    // that doesn't take into account any projection transforms that both spatial nodes are children of.
+                    // Instead, we first project from the element to the world space and get a flattened 2D bounding rect
+                    // in the screen space, we then map this rect from the world space to the backdrop space to get the
+                    // proper bounding box where the backdrop-filter needs to be processed.
+
+                    let prim_to_world_mapper = SpaceMapper::new_with_target(
+                        ROOT_SPATIAL_NODE_INDEX,
+                        spatial_node_index,
+                        LayoutRect::max_rect(),
+                        frame_context.clip_scroll_tree,
+                    );
+
+                    let backdrop_to_world_mapper = SpaceMapper::new_with_target(
+                        ROOT_SPATIAL_NODE_INDEX,
+                        prim_instance.spatial_node_index,
+                        LayoutRect::max_rect(),
+                        frame_context.clip_scroll_tree,
+                    );
+
+                    // First map to the screen and get a flattened rect
+                    let prim_rect = prim_to_world_mapper.map(&prim_data.kind.border_rect).unwrap_or_else(LayoutRect::zero);
+                    // Backwards project the flattened rect onto the backdrop
+                    let prim_rect = backdrop_to_world_mapper.unmap(&prim_rect).unwrap_or_else(LayoutRect::zero);
+
+                    // TODO(aosmond): Is this safe? Updating the primitive size during
+                    // frame building is usually problematic since scene building will cache
+                    // the primitive information in the GPU already.
+                    prim_instance.prim_origin = prim_rect.origin;
+                    prim_data.common.prim_size = prim_rect.size;
+                    prim_instance.local_clip_rect = prim_rect;
+
+                    // Update the cluster bounding rect now that we have the backdrop rect.
+                    let cluster = &mut self.prim_list.clusters[prim_instance.cluster_index.0 as usize];
+                    cluster.bounding_rect = cluster.bounding_rect.union(&prim_rect);
+                }
+                _ => {
+                    panic!("BUG: unexpected deferred primitive kind for cluster updates");
+                }
+            }
+        }
+
         for cluster in &mut self.prim_list.clusters {
             // Skip the cluster if backface culled.
             if !cluster.is_backface_visible {
@@ -3510,11 +3571,6 @@ impl PicturePrimitive {
             let surface_index = state.pop_surface();
             debug_assert_eq!(surface_index, raster_config.surface_index);
 
-            // Snapping may change the local rect slightly, and as such should just be
-            // considered an estimated size for determining if we need raster roots and
-            // preparing the tile cache.
-            self.unsnapped_local_rect = surface_rect;
-
             // Check if any of the surfaces can't be rasterized in local space but want to.
             if raster_config.establishes_raster_root {
                 if surface_rect.size.width > MAX_SURFACE_SIZE ||
@@ -3525,6 +3581,8 @@ impl PicturePrimitive {
                 }
             }
 
+            self.local_rect = surface_rect;
+
             // Drop shadows draw both a content and shadow rect, so need to expand the local
             // rect of any surfaces to be composited in parent surfaces correctly.
             match raster_config.composite_mode {
@@ -3593,14 +3651,14 @@ impl PicturePrimitive {
                         // Basic brush primitive header is (see end of prepare_prim_for_render_inner in prim_store.rs)
                         //  [brush specific data]
                         //  [segment_rect, segment data]
-                        let shadow_rect = self.snapped_local_rect.translate(shadow.offset);
+                        let shadow_rect = self.local_rect.translate(shadow.offset);
 
                         // ImageBrush colors
                         request.push(shadow.color.premultiplied());
                         request.push(PremultipliedColorF::WHITE);
                         request.push([
-                            self.snapped_local_rect.size.width,
+                            self.local_rect.size.width,
-                            self.snapped_local_rect.size.height,
+                            self.local_rect.size.height,
                             0.0,
                             0.0,
                         ]);

gfx/wr/webrender/src/prim_store/mod.rs

@@ -22,7 +22,7 @@ use crate::frame_builder::{FrameBuildingContext, FrameBuildingState, PictureCont
 use crate::frame_builder::{FrameVisibilityContext, FrameVisibilityState};
 use crate::glyph_rasterizer::GlyphKey;
 use crate::gpu_cache::{GpuCache, GpuCacheAddress, GpuCacheHandle, GpuDataRequest, ToGpuBlocks};
-use crate::gpu_types::{BrushFlags, SnapOffsets};
+use crate::gpu_types::{BrushFlags};
 use crate::image::{Repetition};
 use crate::intern;
 use crate::internal_types::PlaneSplitAnchor;
@@ -933,7 +933,6 @@ impl BrushSegment {
         frame_state: &mut FrameBuildingState,
         clip_data_store: &mut ClipDataStore,
         unclipped: &DeviceRect,
-        prim_snap_offsets: SnapOffsets,
         device_pixel_scale: DevicePixelScale,
     ) -> ClipMaskKind {
         match clip_chain {
@@ -956,9 +955,8 @@ impl BrushSegment {
                 // Get a minimal device space rect, clipped to the screen that we
                 // need to allocate for the clip mask, as well as interpolated
                 // snap offsets.
-                let (device_rect, snap_offsets) = match get_clipped_device_rect(
+                let device_rect = match get_clipped_device_rect(
                     unclipped,
-                    prim_snap_offsets,
                     &pic_state.map_raster_to_world,
                     segment_world_rect,
                     device_pixel_scale,
@@ -978,7 +976,6 @@ impl BrushSegment {
                     frame_state.resource_cache,
                     frame_state.render_tasks,
                     clip_data_store,
-                    snap_offsets,
                     device_pixel_scale,
                     frame_context.fb_config,
                 );
@@ -1436,18 +1433,6 @@ pub struct PrimitiveVisibility {
     /// The current combined local clip for this primitive, from
     /// the primitive local clip above and the current clip chain.
     pub combined_local_clip_rect: LayoutRect,
-
-    /// The snap offsets in device space for this primitive. They are
-    /// generated based on the visible rect, which is the local rect
-    /// clipped by the combined local clip for most primitives, or
-    /// just the local rect for pictures.
-    pub snap_offsets: SnapOffsets,
-
-    /// The snap offsets in device space for the drop shadow for
-    /// picture primitives, if applicable. Similar to snap offsets,
-    /// they are generated based on the local rect translated by the
-    /// drop shadow offset.
-    pub shadow_snap_offsets: SnapOffsets,
 }
 
 #[derive(Clone, Debug)]
@@ -1808,7 +1793,7 @@ impl PrimitiveStore {
         world_culling_rect: &WorldRect,
         frame_context: &FrameVisibilityContext,
         frame_state: &mut FrameVisibilityState,
-    ) -> Option<PictureRect> {
+    ) {
         let (mut prim_list, surface_index, apply_local_clip_rect, world_culling_rect, is_composite) = {
             let pic = &mut self.pictures[pic_index.0];
             let mut world_culling_rect = *world_culling_rect;
@@ -1828,7 +1813,7 @@ impl PrimitiveStore {
                     // relative transforms have changed, which means we need to
                     // re-map the dependencies of any child primitives.
                     world_culling_rect = tile_cache.pre_update(
-                        PictureRect::from_untyped(&pic.unsnapped_local_rect.to_untyped()),
+                        PictureRect::from_untyped(&pic.local_rect.to_untyped()),
                         surface_index,
                         frame_context,
                         frame_state,
@@ -1862,19 +1847,13 @@ impl PrimitiveStore {
             frame_context.clip_scroll_tree,
         );
 
-        let mut map_local_to_raster = SpaceMapper::new(
-            surface.raster_spatial_node_index,
-            RasterRect::max_rect(),
-        );
-
-        let mut surface_rect = PictureRect::zero();
-
         for prim_instance in &mut prim_list.prim_instances {
             prim_instance.reset();
 
             if prim_instance.is_chased() {
                 #[cfg(debug_assertions)] // needed for ".id" part
                 println!("\tpreparing {:?} in {:?}", prim_instance.id, pic_index);
+                println!("\t{:?}", prim_instance.kind);
             }
 
             // Get the cluster and see if is visible
@@ -1890,12 +1869,7 @@ impl PrimitiveStore {
                 frame_context.clip_scroll_tree,
             );
 
-            map_local_to_raster.set_target_spatial_node(
+            let (is_passthrough, prim_local_rect, prim_shadow_rect) = match prim_instance.kind {
-                prim_instance.spatial_node_index,
-                frame_context.clip_scroll_tree,
-            );
-
-            let (is_passthrough, snap_to_visible, prim_local_rect, prim_shadow_rect) = match prim_instance.kind {
                 PrimitiveInstanceKind::PushClipChain => {
                     frame_state.clip_chain_stack.push_clip(
                         prim_instance.clip_chain_id,
@@ -1917,7 +1891,7 @@ impl PrimitiveStore {
                         frame_state.clip_store,
                     );
 
-                    let pic_surface_rect = self.update_visibility(
+                    self.update_visibility(
                         pic_index,
                         surface_index,
                         &world_culling_rect,
@@ -1927,8 +1901,6 @@ impl PrimitiveStore {
 
                     frame_state.clip_chain_stack.pop_clip();
 
-                    let pic = &self.pictures[pic_index.0];
-
                     // The local rect of pictures is calculated dynamically based on
                     // the content of children, which may move due to the spatial
                     // node they are attached to. Other parts of the code (such as
@@ -1938,74 +1910,22 @@ impl PrimitiveStore {
                     //           this way. In future, we could perhaps just store the
                     //           size in the picture primitive, to that there isn't
                     //           any duplicated data.
-                    prim_instance.prim_origin = pic.snapped_local_rect.origin;
+                    let pic = &self.pictures[pic_index.0];
+                    prim_instance.prim_origin = pic.local_rect.origin;
 
-                    let shadow_rect = match pic.raster_config {
+                    let shadow_rect = if let Some(RasterConfig { composite_mode: PictureCompositeMode::Filter(Filter::DropShadows(ref shadows)), .. }) = pic.raster_config {
-                        Some(ref rc) => match rc.composite_mode {
                         // If we have a drop shadow filter, we also need to include the shadow in
                         // our local rect for the purpose of calculating the size of the picture.
-                            PictureCompositeMode::Filter(Filter::DropShadows(ref shadows)) => {
                         let mut rect = LayoutRect::zero();
                         for shadow in shadows {
-                                    rect = rect.union(&pic.snapped_local_rect.translate(shadow.offset));
+                            rect = rect.union(&pic.local_rect.translate(shadow.offset));
                         }
-
                         rect
-                            }
+                    } else {
-                            _ => LayoutRect::zero(),
-                        }
-                        None => {
-                            if let Some(ref rect) = pic_surface_rect {
-                                surface_rect = surface_rect.union(rect);
-                            }
                         LayoutRect::zero()
-                        }
                     };
 
-                    if prim_instance.is_chased() {
+                    (pic.raster_config.is_none(), pic.local_rect, shadow_rect)
-                        if pic.unsnapped_local_rect != pic.snapped_local_rect {
-                            println!("\tsnapped from {:?} to {:?}", pic.unsnapped_local_rect, pic.snapped_local_rect);
-                        }
-                    }
-
-                    (pic.raster_config.is_none(), false, pic.snapped_local_rect, shadow_rect)
-                }
-                PrimitiveInstanceKind::Backdrop { data_handle } => {
-                    // The actual size and clip rect of this primitive are determined by computing the bounding
-                    // box of the projected rect of the backdrop-filter element onto the backdrop.
-                    let prim_data = &mut frame_state.data_stores.backdrop[data_handle];
-                    let spatial_node_index = prim_data.kind.spatial_node_index;
-
-                    // We cannot use the relative transform between the backdrop and the element because
-                    // that doesn't take into account any projection transforms that both spatial nodes are children of.
-                    // Instead, we first project from the element to the world space and get a flattened 2D bounding rect
-                    // in the screen space, we then map this rect from the world space to the backdrop space to get the
-                    // proper bounding box where the backdrop-filter needs to be processed.
-
-                    let prim_to_world_mapper = SpaceMapper::new_with_target(
-                        ROOT_SPATIAL_NODE_INDEX,
-                        spatial_node_index,
-                        LayoutRect::max_rect(),
-                        frame_context.clip_scroll_tree,
-                    );
-
-                    let backdrop_to_world_mapper = SpaceMapper::new_with_target(
-                        ROOT_SPATIAL_NODE_INDEX,
-                        prim_instance.spatial_node_index,
-                        LayoutRect::max_rect(),
-                        frame_context.clip_scroll_tree,
-                    );
-
-                    // First map to the screen and get a flattened rect
-                    let prim_rect = prim_to_world_mapper.map(&prim_data.kind.border_rect).unwrap_or_else(LayoutRect::zero);
-                    // Backwards project the flattened rect onto the backdrop
-                    let prim_rect = backdrop_to_world_mapper.unmap(&prim_rect).unwrap_or_else(LayoutRect::zero);
-
-                    prim_instance.prim_origin = prim_rect.origin;
-                    prim_data.common.prim_size = prim_rect.size;
-                    prim_instance.local_clip_rect = prim_rect;
-
-                    (false, true, prim_rect, LayoutRect::zero())
                 }
                 _ => {
                     let prim_data = &frame_state.data_stores.as_common_data(&prim_instance);
@@ -2015,7 +1935,7 @@ impl PrimitiveStore {
                         prim_data.prim_size,
                     );
 
-                    (false, true, prim_rect, LayoutRect::zero())
+                    (false, prim_rect, LayoutRect::zero())
                 }
             };
 
@@ -2028,8 +1948,6 @@ impl PrimitiveStore {
                         clip_chain: ClipChainInstance::empty(),
                         clip_task_index: ClipTaskIndex::INVALID,
                         combined_local_clip_rect: LayoutRect::zero(),
-                        snap_offsets: SnapOffsets::empty(),
-                        shadow_snap_offsets: SnapOffsets::empty(),
                         visibility_mask: PrimitiveVisibilityMask::empty(),
                     }
                 );
@@ -2172,56 +2090,6 @@ impl PrimitiveStore {
                     continue;
                 }
 
-                // All pictures must snap to their primitive rect instead of the
-                // visible rect like most primitives. This is because the picture's
-                // visible rect includes the effect of the picture's clip rect,
-                // which was not considered by the picture's children. The primitive
-                // rect however is simply the union of the visible rect of the
-                // children, which they snapped to, which is precisely what we also
-                // need to snap to in order to be consistent.
-                let visible_rect = if snap_to_visible {
-                    match combined_local_clip_rect.intersection(&prim_local_rect) {
-                        Some(r) => r,
-                        None => {
-                            if prim_instance.is_chased() {
-                                println!("\tculled for zero visible rectangle");
-                            }
-                            prim_instance.visibility_info = PrimitiveVisibilityIndex::INVALID;
-                            continue;
-                        }
-                    }
-                } else {
-                    prim_local_rect
-                };
-
-                // This is how primitives get snapped. In general, snapping a picture's
-                // visible rect here will have no effect, but if it is rasterized in its
-                // own space, or it has a blur or drop shadow effect applied, it may
-                // provide a snapping offset.
-                let (snapped_visible_rect, snap_offsets) = get_snapped_rect(
-                    visible_rect,
-                    &map_local_to_raster,
-                    surface.device_pixel_scale,
-                ).unwrap_or((visible_rect, SnapOffsets::empty()));
-
-                let (combined_visible_rect, shadow_snap_offsets) = if !prim_shadow_rect.is_empty() {
-                    let (snapped_shadow_rect, shadow_snap_offsets) = get_snapped_rect(
-                        prim_shadow_rect,
-                        &map_local_to_raster,
-                        surface.device_pixel_scale,
-                    ).unwrap_or((prim_shadow_rect, SnapOffsets::empty()));
-
-                    (snapped_visible_rect.union(&snapped_shadow_rect), shadow_snap_offsets)
-                } else {
-                    (snapped_visible_rect, SnapOffsets::empty())
-                };
-
-                // Include the snapped primitive/picture local rect, including any shadows,
-                // in the area affected by the surface.
-                if let Some(rect) = map_local_to_surface.map(&combined_visible_rect) {
-                    surface_rect = surface_rect.union(&rect);
-                }
-
                 // When the debug display is enabled, paint a colored rectangle around each
                 // primitive.
                 if frame_context.debug_flags.contains(::api::DebugFlags::PRIMITIVE_DBG) {
@@ -2258,8 +2126,6 @@ impl PrimitiveStore {
                         clip_chain,
                         clip_task_index: ClipTaskIndex::INVALID,
                         combined_local_clip_rect,
-                        snap_offsets,
-                        shadow_snap_offsets,
                         visibility_mask: PrimitiveVisibilityMask::empty(),
                     }
                 );
@@ -2290,32 +2156,7 @@ impl PrimitiveStore {
         // TODO(gw): In future, if we support specifying a flag which gets the
         //           stretch size from the segment rect in the shaders, we can
         //           remove this invalidation here completely.
-        if let Some(ref raster_config) = pic.raster_config {
+        if let Some(RasterConfig { composite_mode: PictureCompositeMode::TileCache { .. }, .. }) = pic.raster_config {
-            // Inflate the local bounding rect if required by the filter effect.
-            // This inflaction factor is to be applied to the surface itself.
-            if pic.options.inflate_if_required {
-                surface_rect = raster_config.composite_mode.inflate_picture_rect(surface_rect, surface.inflation_factor);
-            }
-
-            // Layout space for the picture is picture space from the
-            // perspective of its child primitives.
-            let pic_local_rect = surface_rect * Scale::new(1.0);
-            if pic.snapped_local_rect != pic_local_rect {
-                match raster_config.composite_mode {
-                    PictureCompositeMode::Filter(Filter::DropShadows(..)) => {
-                        for handle in &pic.extra_gpu_data_handles {
-                            frame_state.gpu_cache.invalidate(handle);
-                        }
-                    }
-                    _ => {}
-                }
-                // Invalidate any segments built for this picture, since the local
-                // rect has changed.
-                pic.segments_are_valid = false;
-                pic.snapped_local_rect = pic_local_rect;
-            }
-
-            if let PictureCompositeMode::TileCache { .. } = raster_config.composite_mode {
             let mut tile_cache = frame_state.tile_cache.take().unwrap();
 
             // Build the dirty region(s) for this tile cache.
@@ -2328,18 +2169,6 @@ impl PrimitiveStore {
 
             pic.tile_cache = Some(tile_cache);
         }
-
-            None
-        } else {
-            let parent_surface = &frame_context.surfaces[parent_surface_index.0 as usize];
-            let map_surface_to_parent_surface = SpaceMapper::new_with_target(
-                parent_surface.surface_spatial_node_index,
-                surface.surface_spatial_node_index,
-                PictureRect::max_rect(),
-                frame_context.clip_scroll_tree,
-            );
-            map_surface_to_parent_surface.map(&surface_rect)
-        }
     }
 
     fn request_resources_for_prim(
@@ -3316,7 +3145,7 @@ impl PrimitiveStore {
                             splitter,
                             frame_context.clip_scroll_tree,
                             prim_instance.spatial_node_index,
-                            pic.snapped_local_rect,
+                            pic.local_rect,
                             &prim_info.combined_local_clip_rect,
                             frame_state.current_dirty_region().combined,
                             plane_split_anchor,
@@ -3626,13 +3455,15 @@ impl<'a> GpuDataRequest<'a> {
 impl PrimitiveInstance {
     fn build_segments_if_needed(
         &mut self,
-        prim_clip_chain: &ClipChainInstance,
+        prim_info: &PrimitiveVisibility,
         frame_state: &mut FrameBuildingState,
         prim_store: &mut PrimitiveStore,
         data_stores: &DataStores,
         segments_store: &mut SegmentStorage,
         segment_instances_store: &mut SegmentInstanceStorage,
     ) {
+        let prim_clip_chain = &prim_info.clip_chain;
+
         // Usually, the primitive rect can be found from information
         // in the instance and primitive template.
         let mut prim_local_rect = LayoutRect::new(
@@ -3676,7 +3507,7 @@ impl PrimitiveInstance {
 
                     // Override the prim local rect with the dynamically calculated
                     // local rect for the picture.
-                    prim_local_rect = pic.snapped_local_rect;
+                    prim_local_rect = pic.local_rect;
 
                     segment_instance_index
                 } else {
@@ -3863,7 +3694,6 @@ impl PrimitiveInstance {
                 frame_state,
                 &mut data_stores.clip,
                 unclipped,
-                prim_info.snap_offsets,
                 device_pixel_scale,
             );
             clip_mask_instances.push(clip_mask_kind);
@@ -3884,10 +3714,7 @@ impl PrimitiveInstance {
                 let segment_clip_chain = frame_state
                     .clip_store
                     .build_clip_chain_instance(
-                        segment.local_rect.translate(LayoutVector2D::new(
+                        segment.local_rect.translate(self.prim_origin.to_vector()),
-                            self.prim_origin.x,
-                            self.prim_origin.y,
-                        )),
                         &pic_state.map_local_to_pic,
                         &pic_state.map_pic_to_world,
                         &frame_context.clip_scroll_tree,
@@ -3910,7 +3737,6 @@ impl PrimitiveInstance {
                     frame_state,
                     &mut data_stores.clip,
                     unclipped,
-                    prim_info.snap_offsets,
                     device_pixel_scale,
                 );
                 clip_mask_instances.push(clip_mask_kind);
@@ -3949,7 +3775,7 @@ impl PrimitiveInstance {
         };
 
         self.build_segments_if_needed(
-            &prim_info.clip_chain,
+            &prim_info,
             frame_state,
             prim_store,
             data_stores,
@@ -3983,9 +3809,8 @@ impl PrimitiveInstance {
             // Get a minimal device space rect, clipped to the screen that we
             // need to allocate for the clip mask, as well as interpolated
             // snap offsets.
-            if let Some((device_rect, snap_offsets)) = get_clipped_device_rect(
+            if let Some(device_rect) = get_clipped_device_rect(
                 &unclipped,
-                prim_info.snap_offsets,
                 &pic_state.map_raster_to_world,
                 prim_info.clipped_world_rect,
                 device_pixel_scale,
@@ -3999,7 +3824,6 @@ impl PrimitiveInstance {
                     frame_state.resource_cache,
                     frame_state.render_tasks,
                     &mut data_stores.clip,
-                    snap_offsets,
                     device_pixel_scale,
                     frame_context.fb_config,
                 );
@@ -4022,80 +3846,6 @@ impl PrimitiveInstance {
     }
 }
 
-/// Mimics the GLSL mix() function.
-fn mix(x: f32, y: f32, a: f32) -> f32 {
-    x * (1.0 - a) + y * a
-}
-
-/// Given a point within a local rectangle, and the device space corners
-/// of a snapped primitive, return the snap offsets.
-fn compute_snap_offset_impl<PixelSpace>(
-    reference_pos: Point2D<f32, PixelSpace>,
-    reference_rect: Rect<f32, PixelSpace>,
-    prim_top_left: DevicePoint,
-    prim_bottom_right: DevicePoint,
-) -> DeviceVector2D {
-    let normalized_snap_pos = Point2D::<f32, PixelSpace>::new(
-        (reference_pos.x - reference_rect.origin.x) / reference_rect.size.width,
-        (reference_pos.y - reference_rect.origin.y) / reference_rect.size.height,
-    );
-
-    let top_left = DeviceVector2D::new(
-        (prim_top_left.x + 0.5).floor() - prim_top_left.x,
-        (prim_top_left.y + 0.5).floor() - prim_top_left.y,
-    );
-
-    let bottom_right = DeviceVector2D::new(
-        (prim_bottom_right.x + 0.5).floor() - prim_bottom_right.x,
-        (prim_bottom_right.y + 0.5).floor() - prim_bottom_right.y,
-    );
-
-    DeviceVector2D::new(
-        mix(top_left.x, bottom_right.x, normalized_snap_pos.x),
-        mix(top_left.y, bottom_right.y, normalized_snap_pos.y),
-    )
-}
-
-/// Given the snapping offsets for a primitive rectangle, recompute
-/// the snapping offsets to be relative to given local rectangle.
-/// This *must* exactly match the logic in the GLSL
-/// compute_snap_offset function.
-pub fn recompute_snap_offsets<PixelSpace>(
-    local_rect: Rect<f32, PixelSpace>,
-    prim_rect: Rect<f32, PixelSpace>,
-    snap_offsets: SnapOffsets,
-) -> SnapOffsets
-{
-    if prim_rect.is_empty() || snap_offsets.is_empty() {
-        return SnapOffsets::empty();
-    }
-
-    let normalized_top_left = Point2D::<f32, PixelSpace>::new(
-        (local_rect.origin.x - prim_rect.origin.x) / prim_rect.size.width,
-        (local_rect.origin.y - prim_rect.origin.y) / prim_rect.size.height,
-    );
-
-    let normalized_bottom_right = Point2D::<f32, PixelSpace>::new(
-        (local_rect.origin.x + local_rect.size.width - prim_rect.origin.x) / prim_rect.size.width,
-        (local_rect.origin.y + local_rect.size.height - prim_rect.origin.y) / prim_rect.size.height,
-    );
-
-    let top_left = DeviceVector2D::new(
-        mix(snap_offsets.top_left.x, snap_offsets.bottom_right.x, normalized_top_left.x),
-        mix(snap_offsets.top_left.y, snap_offsets.bottom_right.y, normalized_top_left.y),
-    );
-
-    let bottom_right = DeviceVector2D::new(
-        mix(snap_offsets.top_left.x, snap_offsets.bottom_right.x, normalized_bottom_right.x),
-        mix(snap_offsets.top_left.y, snap_offsets.bottom_right.y, normalized_bottom_right.y),
-    );
-
-    SnapOffsets {
-        top_left,
-        bottom_right,
-    }
-}
-
 /// Retrieve the exact unsnapped device space rectangle for a primitive.
 fn get_unclipped_device_rect(
     prim_rect: PictureRect,
@@ -4114,11 +3864,10 @@ fn get_unclipped_device_rect(
 /// scale per-raster-root.
 fn get_clipped_device_rect(
     unclipped: &DeviceRect,
-    prim_snap_offsets: SnapOffsets,
     map_to_world: &SpaceMapper<RasterPixel, WorldPixel>,
     prim_bounding_rect: WorldRect,
     device_pixel_scale: DevicePixelScale,
-) -> Option<(DeviceIntRect, SnapOffsets)> {
+) -> Option<DeviceIntRect> {
     let unclipped_raster_rect = {
         let world_rect = *unclipped * Scale::new(1.0);
         let raster_rect = world_rect * device_pixel_scale.inv();
@@ -4143,28 +3892,7 @@ fn get_clipped_device_rect(
         device_pixel_scale,
     );
 
-    let fx0 = (clipped.origin.x - unclipped.origin.x) / unclipped.size.width;
+    Some(clipped.to_i32())
-    let fy0 = (clipped.origin.y - unclipped.origin.y) / unclipped.size.height;
-
-    let fx1 = (clipped.origin.x + clipped.size.width - unclipped.origin.x) / unclipped.size.width;
-    let fy1 = (clipped.origin.y + clipped.size.height - unclipped.origin.y) / unclipped.size.height;
-
-    let top_left = DeviceVector2D::new(
-        mix(prim_snap_offsets.top_left.x, prim_snap_offsets.bottom_right.x, fx0),
-        mix(prim_snap_offsets.top_left.y, prim_snap_offsets.bottom_right.y, fy0),
-    );
-
-    let bottom_right = DeviceVector2D::new(
-        mix(prim_snap_offsets.top_left.x, prim_snap_offsets.bottom_right.x, fx1),
-        mix(prim_snap_offsets.top_left.y, prim_snap_offsets.bottom_right.y, fy1),
-    );
-
-    let snap_offsets = SnapOffsets {
-        top_left,
-        bottom_right,
-    };
-
-    Some((clipped.to_i32(), snap_offsets))
 }
 
 pub fn get_raster_rects(
@@ -4202,61 +3930,6 @@ pub fn get_raster_rects(
     Some((clipped.to_i32(), unclipped))
 }
 
-/// Snap the given rect in raster space if the transform is
-/// axis-aligned. It return the snapped rect transformed back into the
-/// given pixel space, and the snap offsets in device space.
-pub fn get_snapped_rect<PixelSpace>(
-    prim_rect: Rect<f32, PixelSpace>,
-    map_to_raster: &SpaceMapper<PixelSpace, RasterPixel>,
-    device_pixel_scale: DevicePixelScale,
-) -> Option<(Rect<f32, PixelSpace>, SnapOffsets)> where PixelSpace: fmt::Debug {
-    let is_axis_aligned = match map_to_raster.kind {
-        CoordinateSpaceMapping::Local |
-        CoordinateSpaceMapping::ScaleOffset(..) => true,
-        CoordinateSpaceMapping::Transform(ref transform) => transform.preserves_2d_axis_alignment(),
-    };
-
-    if is_axis_aligned {
-       let raster_rect = map_to_raster.map(&prim_rect)?;
-
-       let device_rect = {
-            let world_rect = raster_rect * Scale::new(1.0);
-            world_rect * device_pixel_scale
-        };
-
-        let top_left = compute_snap_offset_impl(
-            prim_rect.origin,
-            prim_rect,
-            device_rect.origin,
-            device_rect.bottom_right(),
-        );
-
-        let bottom_right = compute_snap_offset_impl(
-            prim_rect.bottom_right(),
-            prim_rect,
-            device_rect.origin,
-            device_rect.bottom_right(),
-        );
-
-        let snap_offsets = SnapOffsets {
-            top_left,
-            bottom_right,
-        };
-
-        let snapped_device_rect = DeviceRect::new(
-            device_rect.origin + top_left,
-            device_rect.size + (bottom_right - top_left).to_size()
-        );
-
-        let snapped_world_rect = snapped_device_rect / device_pixel_scale;
-        let snapped_raster_rect = snapped_world_rect * Scale::new(1.0);
-        let snapped_prim_rect = map_to_raster.unmap(&snapped_raster_rect)?;
-        Some((snapped_prim_rect, snap_offsets))
-    } else {
-        None
-    }
-}
-
 /// Get the inline (horizontal) and block (vertical) sizes
 /// for a given line decoration.
 pub fn get_line_decoration_sizes(

gfx/wr/webrender/src/render_target.rs

@@ -663,7 +663,6 @@ impl RenderTarget for AlphaRenderTarget {
                     task_info.actual_rect,
                     &ctx.screen_world_rect,
                     task_info.device_pixel_scale,
-                    task_info.snap_offsets,
                     target_rect.origin.to_f32(),
                     task_info.actual_rect.origin.to_f32(),
                 );

gfx/wr/webrender/src/render_task.rs

@@ -14,7 +14,7 @@ use crate::filterdata::SFilterData;
 use crate::frame_builder::FrameBuilderConfig;
 use crate::freelist::{FreeList, FreeListHandle, WeakFreeListHandle};
 use crate::gpu_cache::{GpuCache, GpuCacheAddress, GpuCacheHandle};
-use crate::gpu_types::{BorderInstance, ImageSource, UvRectKind, SnapOffsets};
+use crate::gpu_types::{BorderInstance, ImageSource, UvRectKind};
 use crate::internal_types::{CacheTextureId, FastHashMap, LayerIndex, SavedTargetIndex, TextureSource};
 use crate::prim_store::{PictureIndex, PrimitiveVisibilityMask};
 use crate::prim_store::image::ImageCacheKey;
@@ -125,7 +125,6 @@ pub struct CacheMaskTask {
     pub actual_rect: DeviceIntRect,
     pub root_spatial_node_index: SpatialNodeIndex,
     pub clip_node_range: ClipNodeRange,
-    pub snap_offsets: SnapOffsets,
     pub device_pixel_scale: DevicePixelScale,
 }
 
@@ -523,7 +522,6 @@ impl RenderTask {
         resource_cache: &mut ResourceCache,
         render_tasks: &mut RenderTaskGraph,
         clip_data_store: &mut ClipDataStore,
-        snap_offsets: SnapOffsets,
         device_pixel_scale: DevicePixelScale,
         fb_config: &FrameBuilderConfig,
     ) -> Self {
@@ -617,7 +615,6 @@ impl RenderTask {
                 actual_rect: outer_rect,
                 clip_node_range,
                 root_spatial_node_index,
-                snap_offsets,
                 device_pixel_scale,
             }),
             clear_mode,

gfx/wr/webrender/src/renderer.rs

@@ -620,11 +620,6 @@ pub(crate) mod desc {
                 count: 4,
                 kind: VertexAttributeKind::F32,
             },
-            VertexAttribute {
-                name: "aClipSnapOffsets",
-                count: 4,
-                kind: VertexAttributeKind::F32,
-            },
             VertexAttribute {
                 name: "aClipOrigins",
                 count: 4,