Auto merge of #17810 - asajeffrey:script-paint-worklets-speculative-e…

…valuation, r=emilio

Script paint worklets speculative evaluation

<!-- Please describe your changes on the following line: -->

This PR speculatively calls paint worklets during style, which increases the concurrency, since it increases the chance that the cache will have the right result in it when it comes to layout. The speculation is wasted effort if the size of the element has changed, but this is often not the case.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #17486 and #17369.
- [X] These changes do not require tests because it's a performance improvement

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/17810)
<!-- Reviewable:end -->

components/layout/context.rs

@@ -4,7 +4,6 @@
 
 //! Data needed by the layout thread.
 
-use fnv::FnvHashMap;
 use fnv::FnvHasher;
 use gfx::display_list::{WebRenderImageInfo, OpaqueNode};
 use gfx::font_cache_thread::FontCacheThread;
@@ -25,8 +24,8 @@ use std::collections::HashMap;
 use std::hash::BuildHasherDefault;
 use std::sync::{Arc, Mutex};
 use std::thread;
+use style::context::RegisteredSpeculativePainter;
 use style::context::SharedStyleContext;
-use style::properties::PropertyId;
 
 thread_local!(static FONT_CONTEXT_KEY: RefCell<Option<FontContext>> = RefCell::new(None));
 
@@ -73,7 +72,7 @@ pub struct LayoutContext<'a> {
                                                   BuildHasherDefault<FnvHasher>>>>,
 
     /// Paint worklets
-    pub registered_painters: Arc<RwLock<FnvHashMap<Atom, RegisteredPainter>>>,
+    pub registered_painters: &'a RegisteredPainters,
 
     /// A list of in-progress image loads to be shared with the script thread.
     /// A None value means that this layout was not initiated by the script thread.
@@ -179,9 +178,11 @@ impl<'a> LayoutContext<'a> {
     }
 }
 
-/// A registered paint worklet.
-pub struct RegisteredPainter {
-    pub name: Atom,
-    pub properties: FnvHashMap<Atom, PropertyId>,
-    pub painter: Arc<Painter>,
+/// A registered painter
+pub trait RegisteredPainter: RegisteredSpeculativePainter + Painter {}
+
+/// A set of registered painters
+pub trait RegisteredPainters: Sync {
+    /// Look up a painter
+    fn get(&self, name: &Atom) -> Option<&RegisteredPainter>;
 }

components/layout/display_list_builder.rs

@@ -1181,24 +1181,18 @@ impl FragmentDisplayListBuilding for Fragment {
             .map(|argument| argument.to_css_string())
             .collect();
 
-        // Get the painter, and the computed values for its properties.
-        // TODO: less copying.
-        let (properties, painter) = match state.layout_context.registered_painters.read().get(&name) {
-            Some(registered_painter) => (
-                registered_painter.properties
-                    .iter()
+        let mut draw_result = match state.layout_context.registered_painters.get(&name) {
+            Some(painter) => {
+                debug!("Drawing a paint image {}({},{}).", name, size_in_px.width, size_in_px.height);
+                let properties = painter.properties().iter()
                     .filter_map(|(name, id)| id.as_shorthand().err().map(|id| (name, id)))
                     .map(|(name, id)| (name.clone(), style.computed_value_to_string(id)))
-                    .collect(),
-                registered_painter.painter.clone()
-            ),
+                    .collect();
+                painter.draw_a_paint_image(size_in_px, device_pixel_ratio, properties, arguments)
+            },
             None => return debug!("Worklet {} called before registration.", name),
         };
 
-        // TODO: add a one-place cache to avoid drawing the paint image every time.
-        // https://github.com/servo/servo/issues/17369
-        debug!("Drawing a paint image {}({},{}).", name, size_in_px.width, size_in_px.height);
-        let mut draw_result = painter.draw_a_paint_image(size_in_px, device_pixel_ratio, properties, arguments);
         let webrender_image = WebRenderImageInfo {
             width: draw_result.width,
             height: draw_result.height,

components/layout_thread/Cargo.toml

@@ -41,4 +41,5 @@ servo_config = {path = "../config"}
 servo_geometry = {path = "../geometry"}
 servo_url = {path = "../url"}
 style = {path = "../style"}
+style_traits = {path = "../style_traits"}
 webrender_api = {git = "https://github.com/servo/webrender", features = ["ipc"]}

components/layout_thread/lib.rs

@@ -46,14 +46,15 @@ extern crate servo_config;
 extern crate servo_geometry;
 extern crate servo_url;
 extern crate style;
+extern crate style_traits;
 extern crate webrender_api;
 
 mod dom_wrapper;
 
 use app_units::Au;
 use dom_wrapper::{ServoLayoutElement, ServoLayoutDocument, ServoLayoutNode};
 use dom_wrapper::drop_style_and_layout_data;
-use euclid::{Point2D, Rect, Size2D, ScaleFactor};
+use euclid::{Point2D, Rect, Size2D, ScaleFactor, TypedSize2D};
 use fnv::FnvHashMap;
 use gfx::display_list::{OpaqueNode, WebRenderImageInfo};
 use gfx::font;
@@ -67,6 +68,7 @@ use layout::animation;
 use layout::construct::ConstructionResult;
 use layout::context::LayoutContext;
 use layout::context::RegisteredPainter;
+use layout::context::RegisteredPainters;
 use layout::context::heap_size_of_persistent_local_context;
 use layout::display_list_builder::ToGfxColor;
 use layout::flow::{self, Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
@@ -99,6 +101,8 @@ use script_layout_interface::rpc::TextIndexResponse;
 use script_layout_interface::wrapper_traits::LayoutNode;
 use script_traits::{ConstellationControlMsg, LayoutControlMsg, LayoutMsg as ConstellationMsg};
 use script_traits::{ScrollState, UntrustedNodeAddress};
+use script_traits::DrawAPaintImageResult;
+use script_traits::Painter;
 use selectors::Element;
 use servo_arc::Arc as ServoArc;
 use servo_atoms::Atom;
@@ -122,6 +126,8 @@ use std::thread;
 use style::animation::Animation;
 use style::context::{QuirksMode, ReflowGoal, SharedStyleContext};
 use style::context::{StyleSystemOptions, ThreadLocalStyleContextCreationInfo};
+use style::context::RegisteredSpeculativePainter;
+use style::context::RegisteredSpeculativePainters;
 use style::dom::{ShowSubtree, ShowSubtreeDataAndPrimaryValues, TElement, TNode};
 use style::error_reporting::{NullReporter, RustLogReporter};
 use style::invalidation::element::restyle_hints::RestyleHint;
@@ -137,6 +143,9 @@ use style::thread_state;
 use style::timer::Timer;
 use style::traversal::{DomTraversal, TraversalDriver};
 use style::traversal_flags::TraversalFlags;
+use style_traits::CSSPixel;
+use style_traits::DevicePixel;
+use style_traits::SpeculativePainter;
 
 /// Information needed by the layout thread.
 pub struct LayoutThread {
@@ -235,9 +244,9 @@ pub struct LayoutThread {
 
     webrender_image_cache: Arc<RwLock<FnvHashMap<(ServoUrl, UsePlaceholder),
                                                  WebRenderImageInfo>>>,
-    /// The executor for paint worklets.
-    /// Will be None if the script thread hasn't added any paint worklet modules.
-    registered_painters: Arc<RwLock<FnvHashMap<Atom, RegisteredPainter>>>,
+
+    /// The executors for paint worklets.
+    registered_painters: RegisteredPaintersImpl,
 
     /// Webrender interface.
     webrender_api: webrender_api::RenderApi,
@@ -520,7 +529,7 @@ impl LayoutThread {
             constellation_chan: constellation_chan.clone(),
             time_profiler_chan: time_profiler_chan,
             mem_profiler_chan: mem_profiler_chan,
-            registered_painters: Arc::new(RwLock::new(FnvHashMap::default())),
+            registered_painters: RegisteredPaintersImpl(FnvHashMap::default()),
             image_cache: image_cache.clone(),
             font_cache_thread: font_cache_thread,
             first_reflow: Cell::new(true),
@@ -605,6 +614,7 @@ impl LayoutThread {
                 visited_styles_enabled: false,
                 running_animations: self.running_animations.clone(),
                 expired_animations: self.expired_animations.clone(),
+                registered_speculative_painters: &self.registered_painters,
                 local_context_creation_data: Mutex::new(thread_local_style_context_creation_data),
                 timer: self.timer.clone(),
                 quirks_mode: self.quirks_mode.unwrap(),
@@ -616,7 +626,7 @@ impl LayoutThread {
             webrender_image_cache: self.webrender_image_cache.clone(),
             pending_images: if script_initiated_layout { Some(Mutex::new(vec![])) } else { None },
             newly_transitioning_nodes: if script_initiated_layout { Some(Mutex::new(vec![])) } else { None },
-            registered_painters: self.registered_painters.clone(),
+            registered_painters: &self.registered_painters,
         }
     }
 
@@ -738,13 +748,12 @@ impl LayoutThread {
                     .filter_map(|name| PropertyId::parse(&*name).ok().map(|id| (name.clone(), id)))
                     .filter(|&(_, ref id)| id.as_shorthand().is_err())
                     .collect();
-                let registered_painter = RegisteredPainter {
+                let registered_painter = RegisteredPainterImpl {
                     name: name.clone(),
                     properties: properties,
                     painter: painter,
                 };
-                self.registered_painters.write()
-                    .insert(name, registered_painter);
+                self.registered_painters.0.insert(name, registered_painter);
             },
             Msg::PrepareToExit(response_chan) => {
                 self.prepare_to_exit(response_chan);
@@ -1790,3 +1799,52 @@ lazy_static! {
         }
     };
 }
+
+struct RegisteredPainterImpl {
+    painter: Box<Painter>,
+    name: Atom,
+    properties: FnvHashMap<Atom, PropertyId>,
+}
+
+impl SpeculativePainter for RegisteredPainterImpl {
+    fn speculatively_draw_a_paint_image(&self, properties: Vec<(Atom, String)>, arguments: Vec<String>) {
+        self.painter.speculatively_draw_a_paint_image(properties, arguments);
+    }
+}
+
+impl RegisteredSpeculativePainter for RegisteredPainterImpl {
+    fn properties(&self) -> &FnvHashMap<Atom, PropertyId> {
+        &self.properties
+    }
+    fn name(&self) -> Atom {
+        self.name.clone()
+    }
+}
+
+impl Painter for RegisteredPainterImpl {
+    fn draw_a_paint_image(&self,
+                          size: TypedSize2D<f32, CSSPixel>,
+                          device_pixel_ratio: ScaleFactor<f32, CSSPixel, DevicePixel>,
+                          properties: Vec<(Atom, String)>,
+                          arguments: Vec<String>)
+                          -> DrawAPaintImageResult
+    {
+        self.painter.draw_a_paint_image(size, device_pixel_ratio, properties, arguments)
+    }
+}
+
+impl RegisteredPainter for RegisteredPainterImpl {}
+
+struct RegisteredPaintersImpl(FnvHashMap<Atom, RegisteredPainterImpl>);
+
+impl RegisteredSpeculativePainters for RegisteredPaintersImpl  {
+    fn get(&self, name: &Atom) -> Option<&RegisteredSpeculativePainter> {
+        self.0.get(&name).map(|painter| painter as &RegisteredSpeculativePainter)
+    }
+}
+
+impl RegisteredPainters for RegisteredPaintersImpl {
+    fn get(&self, name: &Atom) -> Option<&RegisteredPainter> {
+        self.0.get(&name).map(|painter| painter as &RegisteredPainter)
+    }
+}

components/script/dom/bindings/trace.rs

@@ -43,7 +43,7 @@ use dom::bindings::str::{DOMString, USVString};
 use dom::bindings::utils::WindowProxyHandler;
 use dom::document::PendingRestyle;
 use encoding::types::EncodingRef;
-use euclid::{Transform2D, Transform3D, Point2D, Vector2D, Rect, Size2D, ScaleFactor};
+use euclid::{Transform2D, Transform3D, Point2D, Vector2D, Rect, TypedSize2D, ScaleFactor};
 use euclid::Length as EuclidLength;
 use html5ever::{Prefix, LocalName, Namespace, QualName};
 use html5ever::buffer_queue::BufferQueue;
@@ -75,6 +75,7 @@ use script_layout_interface::reporter::CSSErrorReporter;
 use script_layout_interface::rpc::LayoutRPC;
 use script_traits::{DocumentActivity, TimerEventId, TimerSource, TouchpadPressurePhase};
 use script_traits::{UntrustedNodeAddress, WindowSizeData, WindowSizeType};
+use script_traits::DrawAPaintImageResult;
 use selectors::matching::ElementSelectorFlags;
 use serde::{Deserialize, Serialize};
 use servo_arc::Arc as ServoArc;
@@ -389,6 +390,7 @@ unsafe_no_jsmanaged_fields!(RelativePos);
 unsafe_no_jsmanaged_fields!(OpaqueStyleAndLayoutData);
 unsafe_no_jsmanaged_fields!(PathBuf);
 unsafe_no_jsmanaged_fields!(CSSErrorReporter);
+unsafe_no_jsmanaged_fields!(DrawAPaintImageResult);
 unsafe_no_jsmanaged_fields!(WebGLBufferId);
 unsafe_no_jsmanaged_fields!(WebGLFramebufferId);
 unsafe_no_jsmanaged_fields!(WebGLProgramId);
@@ -519,7 +521,14 @@ unsafe impl JSTraceable for Rect<f32> {
     }
 }
 
-unsafe impl JSTraceable for Size2D<i32> {
+unsafe impl<U> JSTraceable for TypedSize2D<i32, U> {
+    #[inline]
+    unsafe fn trace(&self, _trc: *mut JSTracer) {
+        // Do nothing
+    }
+}
+
+unsafe impl<U> JSTraceable for TypedSize2D<f32, U> {
     #[inline]
     unsafe fn trace(&self, _trc: *mut JSTracer) {
         // Do nothing