1 files changed, 420 insertions, 0 deletions
diff --git a/gfx/wr/webrender/src/hit_test.rs b/gfx/wr/webrender/src/hit_test.rs
new file mode 100644
index 0000000000..34a7e7e404
--- /dev/null
+++ b/gfx/wr/webrender/src/hit_test.rs
@@ -0,0 +1,420 @@
+/* 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/. */
+
+use api::{BorderRadius, ClipMode, HitTestResultItem, HitTestResult, ItemTag, PrimitiveFlags};
+use api::{PipelineId, ApiHitTester};
+use api::units::*;
+use crate::clip::{rounded_rectangle_contains_point, ClipNodeId, ClipTreeBuilder};
+use crate::clip::{polygon_contains_point, ClipItemKey, ClipItemKeyKind};
+use crate::prim_store::PolygonKey;
+use crate::scene_builder_thread::Interners;
+use crate::spatial_tree::{SpatialNodeIndex, SpatialTree, get_external_scroll_offset};
+use crate::internal_types::{FastHashMap, LayoutPrimitiveInfo};
+use std::sync::{Arc, Mutex};
+use crate::util::{LayoutToWorldFastTransform};
+
+pub struct SharedHitTester {
+    // We don't really need a mutex here. We could do with some sort of
+    // atomic-atomic-ref-counted pointer (an Arc which would let the pointer
+    // be swapped atomically like an AtomicPtr).
+    // In practive this shouldn't cause performance issues, though.
+    hit_tester: Mutex<Arc<HitTester>>,
+}
+
+impl SharedHitTester {
+    pub fn new() -> Self {
+        SharedHitTester {
+            hit_tester: Mutex::new(Arc::new(HitTester::empty())),
+        }
+    }
+
+    pub fn get_ref(&self) -> Arc<HitTester> {
+        let guard = self.hit_tester.lock().unwrap();
+        Arc::clone(&*guard)
+    }
+
+    pub(crate) fn update(&self, new_hit_tester: Arc<HitTester>) {
+        let mut guard = self.hit_tester.lock().unwrap();
+        *guard = new_hit_tester;
+    }
+}
+
+impl ApiHitTester for SharedHitTester {
+    fn hit_test(&self,
+        point: WorldPoint,
+    ) -> HitTestResult {
+        self.get_ref().hit_test(HitTest::new(point))
+    }
+}
+
+/// A copy of important spatial node data to use during hit testing. This a copy of
+/// data from the SpatialTree that will persist as a new frame is under construction,
+/// allowing hit tests consistent with the currently rendered frame.
+#[derive(MallocSizeOf)]
+struct HitTestSpatialNode {
+    /// The pipeline id of this node.
+    pipeline_id: PipelineId,
+
+    /// World transform for content transformed by this node.
+    world_content_transform: LayoutToWorldFastTransform,
+
+    /// World viewport transform for content transformed by this node.
+    world_viewport_transform: LayoutToWorldFastTransform,
+
+    /// The accumulated external scroll offset for this spatial node.
+    external_scroll_offset: LayoutVector2D,
+}
+
+#[derive(MallocSizeOf)]
+struct HitTestClipNode {
+    /// A particular point must be inside all of these regions to be considered clipped in
+    /// for the purposes of a hit test.
+    region: HitTestRegion,
+    /// The positioning node for this clip
+    spatial_node_index: SpatialNodeIndex,
+    /// Parent clip node
+    parent: ClipNodeId,
+}
+
+impl HitTestClipNode {
+    fn new(
+        item: &ClipItemKey,
+        interners: &Interners,
+        parent: ClipNodeId,
+    ) -> Self {
+        let region = match item.kind {
+            ClipItemKeyKind::Rectangle(rect, mode) => {
+                HitTestRegion::Rectangle(rect.into(), mode)
+            }
+            ClipItemKeyKind::RoundedRectangle(rect, radius, mode) => {
+                HitTestRegion::RoundedRectangle(rect.into(), radius.into(), mode)
+            }
+            ClipItemKeyKind::ImageMask(rect, _, polygon_handle) => {
+                if let Some(handle) = polygon_handle {
+                    // Retrieve the polygon data from the interner.
+                    let polygon = &interners.polygon[handle];
+                    HitTestRegion::Polygon(rect.into(), *polygon)
+                } else {
+                    HitTestRegion::Rectangle(rect.into(), ClipMode::Clip)
+                }
+            }
+            ClipItemKeyKind::BoxShadow(..) => HitTestRegion::Invalid,
+        };
+
+        HitTestClipNode {
+            region,
+            spatial_node_index: item.spatial_node_index,
+            parent,
+        }
+    }
+}
+
+#[derive(Clone, MallocSizeOf)]
+struct HitTestingItem {
+    rect: LayoutRect,
+    tag: ItemTag,
+    animation_id: u64,
+    is_backface_visible: bool,
+    spatial_node_index: SpatialNodeIndex,
+    clip_node_id: ClipNodeId,
+}
+
+impl HitTestingItem {
+    fn new(
+        tag: ItemTag,
+        animation_id: u64,
+        info: &LayoutPrimitiveInfo,
+        spatial_node_index: SpatialNodeIndex,
+        clip_node_id: ClipNodeId,
+    ) -> HitTestingItem {
+        HitTestingItem {
+            rect: info.rect,
+            tag,
+            animation_id,
+            is_backface_visible: info.flags.contains(PrimitiveFlags::IS_BACKFACE_VISIBLE),
+            spatial_node_index,
+            clip_node_id,
+        }
+    }
+}
+
+/// Statistics about allocation sizes of current hit tester,
+/// used to pre-allocate size of the next hit tester.
+pub struct HitTestingSceneStats {
+    pub clip_nodes_count: usize,
+    pub items_count: usize,
+}
+
+impl HitTestingSceneStats {
+    pub fn empty() -> Self {
+        HitTestingSceneStats {
+            clip_nodes_count: 0,
+            items_count: 0,
+        }
+    }
+}
+
+#[derive(MallocSizeOf, Debug, Copy, Clone)]
+pub struct ClipNodeIndex(u32);
+
+/// Defines the immutable part of a hit tester for a given scene.
+/// The hit tester is recreated each time a frame is built, since
+/// it relies on the current values of the spatial tree.
+/// However, the clip chain and item definitions don't change,
+/// so they are created once per scene, and shared between
+/// hit tester instances via Arc.
+#[derive(MallocSizeOf)]
+pub struct HitTestingScene {
+    clip_nodes: FastHashMap<ClipNodeId, HitTestClipNode>,
+
+    /// List of hit testing primitives.
+    items: Vec<HitTestingItem>,
+}
+
+impl HitTestingScene {
+    /// Construct a new hit testing scene, pre-allocating to size
+    /// provided by previous scene stats.
+    pub fn new(stats: &HitTestingSceneStats) -> Self {
+        HitTestingScene {
+            clip_nodes: FastHashMap::default(),
+            items: Vec::with_capacity(stats.items_count),
+        }
+    }
+
+    /// Get stats about the current scene allocation sizes.
+    pub fn get_stats(&self) -> HitTestingSceneStats {
+        HitTestingSceneStats {
+            clip_nodes_count: 0,
+            items_count: self.items.len(),
+        }
+    }
+
+    fn add_clip_node(
+        &mut self,
+        clip_node_id: ClipNodeId,
+        clip_tree_builder: &ClipTreeBuilder,
+        interners: &Interners,
+    ) {
+        if clip_node_id == ClipNodeId::NONE {
+            return;
+        }
+
+        if !self.clip_nodes.contains_key(&clip_node_id) {
+            let src_clip_node = clip_tree_builder.get_node(clip_node_id);
+            let clip_item = &interners.clip[src_clip_node.handle];
+
+            let clip_node = HitTestClipNode::new(
+                &clip_item.key,
+                interners,
+                src_clip_node.parent,
+            );
+
+            self.clip_nodes.insert(clip_node_id, clip_node);
+
+            self.add_clip_node(
+                src_clip_node.parent,
+                clip_tree_builder,
+                interners,
+            );
+        }
+    }
+
+    /// Add a hit testing primitive.
+    pub fn add_item(
+        &mut self,
+        tag: ItemTag,
+        anim_id: u64,
+        info: &LayoutPrimitiveInfo,
+        spatial_node_index: SpatialNodeIndex,
+        clip_node_id: ClipNodeId,
+        clip_tree_builder: &ClipTreeBuilder,
+        interners: &Interners,
+    ) {
+        self.add_clip_node(
+            clip_node_id,
+            clip_tree_builder,
+            interners,
+        );
+
+        let item = HitTestingItem::new(
+            tag,
+            anim_id,
+            info,
+            spatial_node_index,
+            clip_node_id,
+        );
+
+        self.items.push(item);
+    }
+}
+
+#[derive(MallocSizeOf)]
+enum HitTestRegion {
+    Invalid,
+    Rectangle(LayoutRect, ClipMode),
+    RoundedRectangle(LayoutRect, BorderRadius, ClipMode),
+    Polygon(LayoutRect, PolygonKey),
+}
+
+impl HitTestRegion {
+    fn contains(&self, point: &LayoutPoint) -> bool {
+        match *self {
+            HitTestRegion::Rectangle(ref rectangle, ClipMode::Clip) =>
+                rectangle.contains(*point),
+            HitTestRegion::Rectangle(ref rectangle, ClipMode::ClipOut) =>
+                !rectangle.contains(*point),
+            HitTestRegion::RoundedRectangle(rect, radii, ClipMode::Clip) =>
+                rounded_rectangle_contains_point(point, &rect, &radii),
+            HitTestRegion::RoundedRectangle(rect, radii, ClipMode::ClipOut) =>
+                !rounded_rectangle_contains_point(point, &rect, &radii),
+            HitTestRegion::Polygon(rect, polygon) =>
+                polygon_contains_point(point, &rect, &polygon),
+            HitTestRegion::Invalid => true,
+        }
+    }
+}
+
+#[derive(MallocSizeOf)]
+pub struct HitTester {
+    #[ignore_malloc_size_of = "Arc"]
+    scene: Arc<HitTestingScene>,
+    spatial_nodes: FastHashMap<SpatialNodeIndex, HitTestSpatialNode>,
+}
+
+impl HitTester {
+    pub fn empty() -> Self {
+        HitTester {
+            scene: Arc::new(HitTestingScene::new(&HitTestingSceneStats::empty())),
+            spatial_nodes: FastHashMap::default(),
+        }
+    }
+
+    pub fn new(
+        scene: Arc<HitTestingScene>,
+        spatial_tree: &SpatialTree,
+    ) -> HitTester {
+        let mut hit_tester = HitTester {
+            scene,
+            spatial_nodes: FastHashMap::default(),
+        };
+        hit_tester.read_spatial_tree(spatial_tree);
+        hit_tester
+    }
+
+    fn read_spatial_tree(
+        &mut self,
+        spatial_tree: &SpatialTree,
+    ) {
+        self.spatial_nodes.clear();
+        self.spatial_nodes.reserve(spatial_tree.spatial_node_count());
+
+        spatial_tree.visit_nodes(|index, node| {
+            //TODO: avoid inverting more than necessary:
+            //  - if the coordinate system is non-invertible, no need to try any of these concrete transforms
+            //  - if there are other places where inversion is needed, let's not repeat the step
+
+            self.spatial_nodes.insert(index, HitTestSpatialNode {
+                pipeline_id: node.pipeline_id,
+                world_content_transform: spatial_tree
+                    .get_world_transform(index)
+                    .into_fast_transform(),
+                world_viewport_transform: spatial_tree
+                    .get_world_viewport_transform(index)
+                    .into_fast_transform(),
+                external_scroll_offset: get_external_scroll_offset(spatial_tree, index),
+            });
+        });
+    }
+
+    pub fn hit_test(&self, test: HitTest) -> HitTestResult {
+        let mut result = HitTestResult::default();
+
+        let mut current_spatial_node_index = SpatialNodeIndex::INVALID;
+        let mut point_in_layer = None;
+
+        // For each hit test primitive
+        for item in self.scene.items.iter().rev() {
+            let scroll_node = &self.spatial_nodes[&item.spatial_node_index];
+            let pipeline_id = scroll_node.pipeline_id;
+
+            // Update the cached point in layer space, if the spatial node
+            // changed since last primitive.
+            if item.spatial_node_index != current_spatial_node_index {
+                point_in_layer = scroll_node
+                    .world_content_transform
+                    .inverse()
+                    .and_then(|inverted| inverted.project_point2d(test.point));
+                current_spatial_node_index = item.spatial_node_index;
+            }
+
+            // Only consider hit tests on transformable layers.
+            let point_in_layer = match point_in_layer {
+                Some(p) => p,
+                None => continue,
+            };
+
+            // If the item's rect or clip rect don't contain this point, it's
+            // not a valid hit.
+            if !item.rect.contains(point_in_layer) {
+                continue;
+            }
+
+            // See if any of the clips for this primitive cull out the item.
+            let mut current_clip_node_id = item.clip_node_id;
+            let mut is_valid = true;
+
+            while current_clip_node_id != ClipNodeId::NONE {
+                let clip_node = &self.scene.clip_nodes[&current_clip_node_id];
+
+                let transform = self
+                    .spatial_nodes[&clip_node.spatial_node_index]
+                    .world_content_transform;
+                if let Some(transformed_point) = transform
+                    .inverse()
+                    .and_then(|inverted| inverted.project_point2d(test.point))
+                {
+                    if !clip_node.region.contains(&transformed_point) {
+                        is_valid = false;
+                        break;
+                    }
+                }
+
+                current_clip_node_id = clip_node.parent;
+            }
+
+            if !is_valid {
+                continue;
+            }
+
+            // Don't hit items with backface-visibility:hidden if they are facing the back.
+            if !item.is_backface_visible && scroll_node.world_content_transform.is_backface_visible() {
+                continue;
+            }
+
+            result.items.push(HitTestResultItem {
+                pipeline: pipeline_id,
+                tag: item.tag,
+                animation_id: item.animation_id,
+            });
+        }
+
+        result.items.dedup();
+        result
+    }
+}
+
+#[derive(MallocSizeOf)]
+pub struct HitTest {
+    point: WorldPoint,
+}
+
+impl HitTest {
+    pub fn new(
+        point: WorldPoint,
+    ) -> HitTest {
+        HitTest {
+            point,
+        }
+    }
+}