auto merge of #3809 : mrobinson/servo/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.

3 files changed, 7 insertions, 5 deletions

diff --git a/components/layout/block.rs b/components/layout/block.rs
index 8835682644d..baf80f6ca3f 100644
--- a/components/layout/block.rs
+++ b/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);
diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index 4a6da7b514b..ae2984f8091 100644
--- a/components/layout/display_list_builder.rs
+++ b/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() {
diff --git a/components/layout/layout_task.rs b/components/layout/layout_task.rs
index 1ed51197db2..e1e918251cd 100644
--- a/components/layout/layout_task.rs
+++ b/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 => {