servo: Merge #3809 - Clip display list based on frame viewport (from mrobinson:display-list-optimization); r=pcwalton

Instead of creating a display list for the entire page, only create one
for an area that expands around the viewport. On my machine this makes
incremental layout of http://timecube.com 50% faster.

Source-Repo: https://github.com/servo/servo
Source-Revision: 26045d7fcbab8851fbefe2851cd904203f8fd8dd

servo/Cargo.lock

@@ -174,7 +174,7 @@ source = "git+https://github.com/servo/libfreetype2#5b6499164106f094937565595c7b
 [[package]]
 name = "geom"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-geom#b001a76e907befaae1d0d6dd259418a22092da86"
+source = "git+https://github.com/servo/rust-geom#e5e74911ac6d3201009879b72499d6c681302611"
 
 [[package]]
 name = "gfx"

servo/components/compositing/compositor.rs

@@ -38,10 +38,12 @@ use layers::scene::Scene;
 use png;
 use gleam::gl::types::{GLint, GLsizei};
 use gleam::gl;
+use script_traits::{ViewportMsg, ScriptControlChan};
 use servo_msg::compositor_msg::{Blank, Epoch, FinishedLoading, IdleRenderState, LayerId};
 use servo_msg::compositor_msg::{ReadyState, RenderingRenderState, RenderState, Scrollable};
-use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, LoadUrlMsg, NavigateMsg};
-use servo_msg::constellation_msg::{LoadData, PipelineId, ResizedWindowMsg, WindowSizeData};
+use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, LoadUrlMsg};
+use servo_msg::constellation_msg::{NavigateMsg, LoadData, PipelineId, ResizedWindowMsg};
+use servo_msg::constellation_msg::{WindowSizeData};
 use servo_msg::constellation_msg;
 use servo_util::geometry::{PagePx, ScreenPx, ViewportPx};
 use servo_util::memory::MemoryProfilerChan;
@@ -266,6 +268,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 self.set_frame_tree(&frame_tree,
                                     response_chan,
                                     new_constellation_chan);
+                self.send_viewport_rects_for_all_layers();
             }
 
             (FrameTreeUpdateMsg(frame_tree_diff, response_channel), NotShuttingDown) => {
@@ -775,6 +778,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
     }
 
     fn process_pending_scroll_events(&mut self) {
+        let had_scroll_events = self.pending_scroll_events.len() > 0;
         for scroll_event in mem::replace(&mut self.pending_scroll_events, Vec::new()).into_iter() {
             let delta = scroll_event.delta / self.scene.scale;
             let cursor = scroll_event.cursor.as_f32() / self.scene.scale;
@@ -789,6 +793,10 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             self.start_scrolling_timer_if_necessary();
             self.send_buffer_requests_for_all_layers();
         }
+
+        if had_scroll_events {
+            self.send_viewport_rects_for_all_layers();
+        }
     }
 
     fn device_pixels_per_screen_px(&self) -> ScaleFactor<ScreenPx, DevicePixel, f32> {
@@ -845,6 +853,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             None => { }
         }
 
+        self.send_viewport_rects_for_all_layers();
         self.composite_if_necessary();
     }
 
@@ -902,6 +911,27 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         }
     }
 
+    fn send_viewport_rect_for_layer(&self, layer: Rc<Layer<CompositorData>>) {
+        if layer.extra_data.borrow().id == LayerId::null() {
+            let layer_rect = Rect(-layer.extra_data.borrow().scroll_offset.to_untyped(),
+                                  layer.bounds.borrow().size.to_untyped());
+            let pipeline = &layer.extra_data.borrow().pipeline;
+            let ScriptControlChan(ref chan) = pipeline.script_chan;
+            chan.send(ViewportMsg(pipeline.id.clone(), layer_rect));
+        }
+
+        for kid in layer.children().iter() {
+            self.send_viewport_rect_for_layer(kid.clone());
+        }
+    }
+
+    fn send_viewport_rects_for_all_layers(&self) {
+        match self.scene.root {
+            Some(ref root) => self.send_viewport_rect_for_layer(root.clone()),
+            None => {},
+        }
+    }
+
     /// Returns true if any buffer requests were sent or false otherwise.
     fn send_buffer_requests_for_all_layers(&mut self) -> bool {
         let mut layers_and_requests = Vec::new();

servo/components/layout/block.rs

@@ -48,7 +48,7 @@ use geom::Size2D;
 use gfx::display_list::BlockLevel;
 use serialize::{Encoder, Encodable};
 use servo_msg::compositor_msg::LayerId;
-use servo_util::geometry::{Au, MAX_AU, MAX_RECT};
+use servo_util::geometry::{Au, MAX_AU};
 use servo_util::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize};
 use servo_util::opts;
 use std::cmp::{max, min};
@@ -1665,10 +1665,6 @@ impl Flow for BlockFlow {
         // FIXME(#2795): Get the real container size
         let container_size = Size2D::zero();
 
-        if self.is_root() {
-            self.base.clip_rect = MAX_RECT;
-        }
-
         if self.base.flags.is_absolutely_positioned() {
             let position_start = self.base.position.start.to_physical(self.base.writing_mode,
                                                                       container_size);

servo/components/layout/display_list_builder.rs

@@ -499,6 +499,10 @@ impl FragmentDisplayListBuilding for Fragment {
             return
         }
 
+        if !absolute_fragment_bounds.intersects(clip_rect) {
+            return;
+        }
+
         debug!("Fragment::build_display_list: intersected. Adding display item...");
 
         if self.is_primary_fragment() {

servo/components/layout/layout_task.rs

@@ -625,6 +625,8 @@ impl LayoutTask {
                 LogicalPoint::zero(writing_mode).to_physical(writing_mode,
                                                              rw_data.screen_size);
 
+            flow::mut_base(layout_root.deref_mut()).clip_rect = data.page_clip_rect;
+
             let rw_data = rw_data.deref_mut();
             match rw_data.parallel_traversal {
                 None => {

servo/components/script/dom/bindings/trace.rs

@@ -28,37 +28,37 @@
 //! a datatype.
 
 use dom::bindings::js::JS;
-use dom::bindings::utils::{Reflectable, Reflector};
+use dom::bindings::utils::{Reflectable, Reflector, WindowProxyHandler};
+use dom::node::{Node, TrustedNodeAddress};
+
+use collections::hash::{Hash, Hasher};
+use geom::rect::Rect;
+use html5ever::tree_builder::QuirksMode;
+use http::headers::request::HeaderCollection as RequestHeaderCollection;
+use http::headers::response::HeaderCollection as ResponseHeaderCollection;
+use http::method::Method;
 use js::jsapi::{JSObject, JSTracer, JS_CallTracer, JSTRACE_OBJECT};
 use js::jsval::JSVal;
-
+use js::rust::Cx;
+use layout_interface::{LayoutRPC, LayoutChan};
 use libc;
-use std::rc::Rc;
-use std::cell::{Cell, RefCell};
-
-use url::Url;
 use msg::constellation_msg::{PipelineId, SubpageId, WindowSizeData};
 use net::image_cache_task::ImageCacheTask;
 use script_traits::ScriptControlChan;
-use std::collections::hashmap::HashMap;
-use collections::hash::{Hash, Hasher};
-use style::PropertyDeclarationBlock;
-use std::comm::{Receiver, Sender};
-use string_cache::{Atom, Namespace};
-use js::rust::Cx;
-use http::headers::response::HeaderCollection as ResponseHeaderCollection;
-use http::headers::request::HeaderCollection as RequestHeaderCollection;
-use http::method::Method;
-use std::io::timer::Timer;
 use script_traits::UntrustedNodeAddress;
 use servo_msg::compositor_msg::ScriptListener;
 use servo_msg::constellation_msg::ConstellationChan;
 use servo_util::smallvec::{SmallVec1, SmallVec};
 use servo_util::str::LengthOrPercentageOrAuto;
-use layout_interface::{LayoutRPC, LayoutChan};
-use dom::node::{Node, TrustedNodeAddress};
-use dom::bindings::utils::WindowProxyHandler;
-use html5ever::tree_builder::QuirksMode;
+use std::cell::{Cell, RefCell};
+use std::collections::hashmap::HashMap;
+use std::comm::{Receiver, Sender};
+use std::io::timer::Timer;
+use std::rc::Rc;
+use string_cache::{Atom, Namespace};
+use style::PropertyDeclarationBlock;
+use url::Url;
+
 
 /// A trait to allow tracing (only) DOM objects.
 pub trait JSTraceable {
@@ -200,6 +200,7 @@ no_jsmanaged_fields!(uint, u8, u16, u32, u64)
 no_jsmanaged_fields!(int, i8, i16, i32, i64)
 no_jsmanaged_fields!(Sender<T>)
 no_jsmanaged_fields!(Receiver<T>)
+no_jsmanaged_fields!(Rect<T>)
 no_jsmanaged_fields!(ImageCacheTask, ScriptControlChan)
 no_jsmanaged_fields!(Atom, Namespace, Timer)
 no_jsmanaged_fields!(PropertyDeclarationBlock)

servo/components/script/layout_interface.rs

@@ -109,6 +109,8 @@ pub struct Reflow {
     pub id: uint,
     /// The type of query if any to perform during this reflow.
     pub query_type: ReflowQueryType,
+    ///  A clipping rectangle for the page, an enlarged rectangle containing the viewport.
+    pub page_clip_rect: Rect<Au>,
 }
 
 /// Encapsulates a channel to the layout task.

servo/components/script/page.rs

@@ -19,19 +19,21 @@ use layout_interface::{
 };
 use script_traits::{UntrustedNodeAddress, ScriptControlChan};
 
-use geom::{Point2D, Rect};
+use geom::{Point2D, Rect, Size2D};
 use js::rust::Cx;
 use servo_msg::compositor_msg::PerformingLayout;
 use servo_msg::compositor_msg::ScriptListener;
 use servo_msg::constellation_msg::{ConstellationChan, WindowSizeData};
 use servo_msg::constellation_msg::{PipelineId, SubpageId};
 use servo_net::resource_task::ResourceTask;
-use servo_util::geometry::Au;
+use servo_util::geometry::{Au, MAX_RECT};
+use servo_util::geometry;
 use servo_util::str::DOMString;
 use servo_util::smallvec::{SmallVec1, SmallVec};
 use std::cell::Cell;
 use std::comm::{channel, Receiver, Empty, Disconnected};
 use std::mem::replace;
+use std::num::abs;
 use std::rc::Rc;
 use url::Url;
 
@@ -98,6 +100,10 @@ pub struct Page {
 
     /// Number of unnecessary potential reflows that were skipped since the last reflow
     pub avoided_reflows: Cell<int>,
+
+    /// An enlarged rectangle around the page contents visible in the viewport, used
+    /// to prevent creating display list items for content that is far away from the viewport.
+    pub page_clip_rect: Cell<Rect<Au>>,
 }
 
 pub struct PageIterator {
@@ -164,6 +170,7 @@ impl Page {
             damaged: Cell::new(false),
             pending_reflows: Cell::new(0),
             avoided_reflows: Cell::new(0),
+            page_clip_rect: Cell::new(MAX_RECT),
         }
     }
 
@@ -236,6 +243,49 @@ impl Page {
         }
         None
     }
+
+    fn should_move_clip_rect(&self, clip_rect: Rect<Au>, new_viewport: Rect<f32>) -> bool{
+        let clip_rect = Rect(Point2D(geometry::to_frac_px(clip_rect.origin.x) as f32,
+                                        geometry::to_frac_px(clip_rect.origin.y) as f32),
+                                Size2D(geometry::to_frac_px(clip_rect.size.width) as f32,
+                                       geometry::to_frac_px(clip_rect.size.height) as f32));
+
+        // We only need to move the clip rect if the viewport is getting near the edge of
+        // our preexisting clip rect. We use half of the size of the viewport as a heuristic
+        // for "close."
+        static VIEWPORT_SCROLL_MARGIN_SIZE: f32 = 0.5;
+        let viewport_scroll_margin = new_viewport.size * VIEWPORT_SCROLL_MARGIN_SIZE;
+
+        abs(clip_rect.origin.x - new_viewport.origin.x) <= viewport_scroll_margin.width ||
+        abs(clip_rect.max_x() - new_viewport.max_x()) <= viewport_scroll_margin.width ||
+        abs(clip_rect.origin.y - new_viewport.origin.y) <= viewport_scroll_margin.height ||
+        abs(clip_rect.max_y() - new_viewport.max_y()) <= viewport_scroll_margin.height
+    }
+
+    pub fn set_page_clip_rect_with_new_viewport(&self, viewport: Rect<f32>) -> bool {
+        // We use a clipping rectangle that is five times the size of the of the viewport,
+        // so that we don't collect display list items for areas too far outside the viewport,
+        // but also don't trigger reflows every time the viewport changes.
+        static VIEWPORT_EXPANSION: f32 = 2.0; // 2 lengths on each side plus original length is 5 total.
+        let proposed_clip_rect = geometry::f32_rect_to_au_rect(
+            viewport.inflate(viewport.size.width * VIEWPORT_EXPANSION,
+            viewport.size.height * VIEWPORT_EXPANSION));
+        let clip_rect = self.page_clip_rect.get();
+        if proposed_clip_rect == clip_rect {
+            return false;
+        }
+
+        let had_clip_rect = clip_rect != MAX_RECT;
+        if had_clip_rect && !self.should_move_clip_rect(clip_rect, viewport) {
+            return false;
+        }
+
+        self.page_clip_rect.set(proposed_clip_rect);
+
+        // If we didn't have a clip rect, the previous display doesn't need rebuilding
+        // because it was built for infinite clip (MAX_RECT).
+        had_clip_rect
+    }
 }
 
 impl Iterator<Rc<Page>> for PageIterator {
@@ -375,6 +425,7 @@ impl Page {
                     script_join_chan: join_chan,
                     id: last_reflow_id.get(),
                     query_type: query_type,
+                    page_clip_rect: self.page_clip_rect.get(),
                 };
 
                 let LayoutChan(ref chan) = self.layout_chan;

servo/components/script/script_task.rs

@@ -40,9 +40,9 @@ use devtools_traits::{DevtoolScriptControlMsg, EvaluateJS, EvaluateJSReply, GetD
 use devtools_traits::{GetChildren, GetLayout};
 use script_traits::{CompositorEvent, ResizeEvent, ReflowEvent, ClickEvent, MouseDownEvent};
 use script_traits::{MouseMoveEvent, MouseUpEvent, ConstellationControlMsg, ScriptTaskFactory};
-use script_traits::{ResizeMsg, AttachLayoutMsg, LoadMsg, SendEventMsg, ResizeInactiveMsg};
-use script_traits::{ExitPipelineMsg, NewLayoutInfo, OpaqueScriptLayoutChannel, ScriptControlChan};
-use script_traits::{ReflowCompleteMsg, UntrustedNodeAddress};
+use script_traits::{ResizeMsg, AttachLayoutMsg, LoadMsg, ViewportMsg, SendEventMsg};
+use script_traits::{ResizeInactiveMsg, ExitPipelineMsg, NewLayoutInfo, OpaqueScriptLayoutChannel};
+use script_traits::{ScriptControlChan, ReflowCompleteMsg, UntrustedNodeAddress};
 use servo_msg::compositor_msg::{FinishedLoading, LayerId, Loading};
 use servo_msg::compositor_msg::{ScriptListener};
 use servo_msg::constellation_msg::{ConstellationChan, LoadCompleteMsg, LoadUrlMsg, NavigationDirection};
@@ -495,6 +495,13 @@ impl ScriptTask {
                     pending.push_all_move(node_addresses);
                     needs_reflow.insert(id);
                 }
+                FromConstellation(ViewportMsg(id, rect)) => {
+                    let mut page = self.page.borrow_mut();
+                    let inner_page = page.find(id).expect("Page rect message sent to nonexistent pipeline");
+                    if inner_page.set_page_clip_rect_with_new_viewport(rect) {
+                        needs_reflow.insert(id);
+                    }
+                }
                 _ => {
                     sequential.push(event);
                 }
@@ -530,6 +537,7 @@ impl ScriptTask {
                 FromConstellation(ReflowCompleteMsg(id, reflow_id)) => self.handle_reflow_complete_msg(id, reflow_id),
                 FromConstellation(ResizeInactiveMsg(id, new_size)) => self.handle_resize_inactive_msg(id, new_size),
                 FromConstellation(ExitPipelineMsg(id)) => if self.handle_exit_pipeline_msg(id) { return false },
+                FromConstellation(ViewportMsg(..)) => fail!("should have handled ViewportMsg already"),
                 FromScript(ExitWindowMsg(id)) => self.handle_exit_window_msg(id),
                 FromConstellation(ResizeMsg(..)) => fail!("should have handled ResizeMsg already"),
                 FromScript(XHRProgressMsg(addr, progress)) => XMLHttpRequest::handle_progress(addr, progress),

servo/components/script_traits/lib.rs

@@ -32,6 +32,7 @@ use servo_util::smallvec::SmallVec1;
 use std::any::Any;
 
 use geom::point::Point2D;
+use geom::rect::Rect;
 
 use serialize::{Encodable, Encoder};
 
@@ -62,6 +63,7 @@ pub enum ConstellationControlMsg {
     SendEventMsg(PipelineId, CompositorEvent),
     /// Notifies script that reflow is finished.
     ReflowCompleteMsg(PipelineId, uint),
+    ViewportMsg(PipelineId, Rect<f32>),
 }
 
 /// Events from the compositor that the script task needs to know about

servo/ports/cef/Cargo.lock

@@ -184,7 +184,7 @@ source = "git+https://github.com/servo/libfreetype2#5b6499164106f094937565595c7b
 [[package]]
 name = "geom"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-geom#b001a76e907befaae1d0d6dd259418a22092da86"
+source = "git+https://github.com/servo/rust-geom#e5e74911ac6d3201009879b72499d6c681302611"
 
 [[package]]
 name = "gfx"