layout: Paint stacking contexts' overflow areas properly.

This was making `box-shadow` not show up in many cases, in particular,
but the effects were not limited to that.

30 files changed, 357 insertions, 179 deletions

diff --git a/components/compositing/compositor_layer.rs b/components/compositing/compositor_layer.rs
index 4c13d7fb8a0..3658172847e 100644
--- a/components/compositing/compositor_layer.rs
+++ b/components/compositing/compositor_layer.rs
@@ -283,8 +283,7 @@ impl CompositorLayer for Layer<CompositorData> {
         self.clamp_scroll_offset_and_scroll_layer(scroll_offset + delta)
     }
 
-    fn clamp_scroll_offset_and_scroll_layer(&self,
-                                            new_offset: TypedPoint2D<LayerPixel, f32>)
+    fn clamp_scroll_offset_and_scroll_layer(&self, new_offset: TypedPoint2D<LayerPixel, f32>)
                                             -> ScrollEventResult {
         let layer_size = self.bounds.borrow().size;
         let content_size = calculate_content_size_for_layer(self);
@@ -339,17 +338,14 @@ impl CompositorLayer for Layer<CompositorData> {
         let _ = chan.send_opt(ConstellationControlMsg::SendEvent(pipeline.id.clone(), message));
     }
 
-    fn scroll_layer_and_all_child_layers(&self,
-                                         new_offset: TypedPoint2D<LayerPixel, f32>)
+    fn scroll_layer_and_all_child_layers(&self, new_offset: TypedPoint2D<LayerPixel, f32>)
                                          -> bool {
         let mut result = false;
 
         // Only scroll this layer if it's not fixed-positioned.
         if self.extra_data.borrow().scroll_policy != FixedPosition {
             let new_offset = new_offset.to_untyped();
-            *self.transform.borrow_mut() = identity().translate(new_offset.x,
-                                                                 new_offset.y,
-                                                                 0.0);
+            *self.transform.borrow_mut() = identity().translate(new_offset.x, new_offset.y, 0.0);
             *self.content_offset.borrow_mut() = Point2D::from_untyped(&new_offset);
             result = true
         }
diff --git a/components/gfx/display_list/mod.rs b/components/gfx/display_list/mod.rs
index af32ffad76b..ecd7b170246 100644
--- a/components/gfx/display_list/mod.rs
+++ b/components/gfx/display_list/mod.rs
@@ -34,7 +34,7 @@ use servo_msg::compositor_msg::LayerId;
 use servo_net::image::base::Image;
 use servo_util::cursor::Cursor;
 use servo_util::dlist as servo_dlist;
-use servo_util::geometry::{mod, Au, MAX_RECT, ZERO_POINT, ZERO_RECT};
+use servo_util::geometry::{mod, Au, MAX_RECT, ZERO_RECT};
 use servo_util::range::Range;
 use servo_util::smallvec::{SmallVec, SmallVec8};
 use std::fmt;
@@ -160,9 +160,8 @@ pub struct StackingContext {
     pub layer: Option<Arc<PaintLayer>>,
     /// The position and size of this stacking context.
     pub bounds: Rect<Au>,
-    /// The clipping rect for this stacking context, in the coordinate system of the *parent*
-    /// stacking context.
-    pub clip_rect: Rect<Au>,
+    /// The overflow rect for this stacking context in its coordinate system.
+    pub overflow: Rect<Au>,
     /// The `z-index` for this stacking context.
     pub z_index: i32,
     /// The opacity of this stacking context.
@@ -171,12 +170,10 @@ pub struct StackingContext {
 
 impl StackingContext {
     /// Creates a new stacking context.
-    ///
-    /// TODO(pcwalton): Stacking contexts should not always be clipped to their bounds, to handle
-    /// overflow properly.
     #[inline]
     pub fn new(display_list: Box<DisplayList>,
-               bounds: Rect<Au>,
+               bounds: &Rect<Au>,
+               overflow: &Rect<Au>,
                z_index: i32,
                opacity: AzFloat,
                layer: Option<Arc<PaintLayer>>)
@@ -184,8 +181,8 @@ impl StackingContext {
         StackingContext {
             display_list: display_list,
             layer: layer,
-            bounds: bounds,
-            clip_rect: Rect(ZERO_POINT, bounds.size),
+            bounds: *bounds,
+            overflow: *overflow,
             z_index: z_index,
             opacity: opacity,
         }
@@ -196,7 +193,7 @@ impl StackingContext {
                                           paint_context: &mut PaintContext,
                                           tile_bounds: &Rect<AzFloat>,
                                           transform: &Matrix2D<AzFloat>,
-                                          clip_rect: Option<Rect<Au>>) {
+                                          clip_rect: Option<&Rect<Au>>) {
         let temporary_draw_target =
             paint_context.get_or_create_temporary_draw_target(self.opacity);
         {
@@ -205,7 +202,7 @@ impl StackingContext {
                 font_ctx: &mut *paint_context.font_ctx,
                 page_rect: paint_context.page_rect,
                 screen_rect: paint_context.screen_rect,
-                clip_rect: clip_rect,
+                clip_rect: clip_rect.map(|clip_rect| *clip_rect),
                 transient_clip: None,
             };
 
@@ -252,7 +249,7 @@ impl StackingContext {
                     positioned_kid.optimize_and_draw_into_context(&mut paint_subcontext,
                                                                   &new_tile_rect,
                                                                   &new_transform,
-                                                                  Some(positioned_kid.clip_rect))
+                                                                  Some(&positioned_kid.overflow))
                 }
             }
 
@@ -295,7 +292,7 @@ impl StackingContext {
                     positioned_kid.optimize_and_draw_into_context(&mut paint_subcontext,
                                                                   &new_tile_rect,
                                                                   &new_transform,
-                                                                  Some(positioned_kid.clip_rect))
+                                                                  Some(&positioned_kid.overflow))
                 }
             }
 
@@ -329,11 +326,18 @@ impl StackingContext {
             }
         };
 
-        let child_stacking_context_bounds = child_stacking_context.bounds.to_azure_rect();
-        let tile_subrect = tile_bounds.intersection(&child_stacking_context_bounds)
+        // Translate the child's overflow region into our coordinate system.
+        let child_stacking_context_overflow =
+            child_stacking_context.overflow.translate(&child_stacking_context.bounds.origin)
+                                           .to_azure_rect();
+
+        // Intersect that with the current tile boundaries to find the tile boundaries that the
+        // child covers.
+        let tile_subrect = tile_bounds.intersection(&child_stacking_context_overflow)
                                       .unwrap_or(ZERO_AZURE_RECT);
-        let offset = tile_subrect.origin - child_stacking_context_bounds.origin;
-        Rect(offset, tile_subrect.size)
+
+        // Translate the resulting rect into the child's coordinate system.
+        tile_subrect.translate(&-child_stacking_context.bounds.to_azure_rect().origin)
     }
 
     /// Places all nodes containing the point of interest into `result`, topmost first. If
diff --git a/components/gfx/display_list/optimizer.rs b/components/gfx/display_list/optimizer.rs
index c0dac718c51..1b7998f86c9 100644
--- a/components/gfx/display_list/optimizer.rs
+++ b/components/gfx/display_list/optimizer.rs
@@ -59,7 +59,8 @@ impl DisplayListOptimizer {
                                              mut stacking_contexts: I)
                                              where I: Iterator<&'a Arc<StackingContext>> {
         for stacking_context in stacking_contexts {
-            if self.visible_rect.intersects(&stacking_context.bounds) {
+            let overflow = stacking_context.overflow.translate(&stacking_context.bounds.origin);
+            if self.visible_rect.intersects(&overflow) {
                 result_list.push_back((*stacking_context).clone())
             }
         }
diff --git a/components/gfx/paint_task.rs b/components/gfx/paint_task.rs
index 1210c34627b..5fdacfa838d 100644
--- a/components/gfx/paint_task.rs
+++ b/components/gfx/paint_task.rs
@@ -148,20 +148,21 @@ fn initialize_layers<C>(compositor: &mut C,
              stacking_context: &StackingContext,
              page_position: &Point2D<Au>) {
         let page_position = stacking_context.bounds.origin + *page_position;
-        match stacking_context.layer {
-            None => {}
-            Some(ref paint_layer) => {
-                metadata.push(LayerMetadata {
-                    id: paint_layer.id,
-                    position:
-                        Rect(Point2D(page_position.x.to_nearest_px() as uint,
-                                     page_position.y.to_nearest_px() as uint),
-                             Size2D(stacking_context.bounds.size.width.to_nearest_px() as uint,
-                                    stacking_context.bounds.size.height.to_nearest_px() as uint)),
-                    background_color: paint_layer.background_color,
-                    scroll_policy: paint_layer.scroll_policy,
-                })
-            }
+        if let Some(ref paint_layer) = stacking_context.layer {
+            // Layers start at the top left of their overflow rect, as far as the info we give to
+            // the compositor is concerned.
+            let overflow_relative_page_position = page_position + stacking_context.overflow.origin;
+            let layer_position =
+                Rect(Point2D(overflow_relative_page_position.x.to_nearest_px() as i32,
+                             overflow_relative_page_position.y.to_nearest_px() as i32),
+                     Size2D(stacking_context.overflow.size.width.to_nearest_px() as i32,
+                            stacking_context.overflow.size.height.to_nearest_px() as i32));
+            metadata.push(LayerMetadata {
+                id: paint_layer.id,
+                position: layer_position,
+                background_color: paint_layer.background_color,
+                scroll_policy: paint_layer.scroll_policy,
+            })
         }
 
         for kid in stacking_context.display_list.children.iter() {
@@ -384,15 +385,14 @@ impl<C> PaintTask<C> where C: PaintListener + Send {
               layer_id: LayerId) {
         profile(TimeProfilerCategory::Painting, None, self.time_profiler_chan.clone(), || {
             // Bail out if there is no appropriate stacking context.
-            let stacking_context = match self.root_stacking_context {
-                Some(ref stacking_context) => {
-                    match display_list::find_stacking_context_with_layer_id(stacking_context,
-                                                                            layer_id) {
-                        Some(stacking_context) => stacking_context,
-                        None => return,
-                    }
+            let stacking_context = if let Some(ref stacking_context) = self.root_stacking_context {
+                match display_list::find_stacking_context_with_layer_id(stacking_context,
+                                                                        layer_id) {
+                    Some(stacking_context) => stacking_context,
+                    None => return,
                 }
-                None => return,
+            } else {
+                return
             };
 
             // Divide up the layer into tiles and distribute them to workers via a simple round-
@@ -547,8 +547,13 @@ impl WorkerThread {
                 transient_clip: None,
             };
 
+            // Apply a translation to start at the boundaries of the stacking context, since the
+            // layer's origin starts at its overflow rect's origin.
+            let tile_bounds = tile.page_rect.translate(
+                &Point2D(stacking_context.overflow.origin.x.to_subpx() as AzFloat,
+                         stacking_context.overflow.origin.y.to_subpx() as AzFloat));
+
             // Apply the translation to paint the tile we want.
-            let tile_bounds = tile.page_rect;
             let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
             let matrix = matrix.scale(scale as AzFloat, scale as AzFloat);
             let matrix = matrix.translate(-tile_bounds.origin.x as AzFloat,
@@ -561,7 +566,7 @@ impl WorkerThread {
             profile(TimeProfilerCategory::PaintingPerTile, None,
                     self.time_profiler_sender.clone(), || {
                 stacking_context.optimize_and_draw_into_context(&mut paint_context,
-                                                                &tile.page_rect,
+                                                                &tile_bounds,
                                                                 &matrix,
                                                                 None);
                 paint_context.draw_target.flush();
diff --git a/components/layout/block.rs b/components/layout/block.rs
index 02b58ce463e..eec1f945d1c 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -41,7 +41,7 @@ use flow::{LAYERS_NEEDED_FOR_DESCENDANTS, NEEDS_LAYER};
 use flow::{IS_ABSOLUTELY_POSITIONED};
 use flow::{CLEARS_LEFT, CLEARS_RIGHT};
 use flow;
-use fragment::{Fragment, FragmentBoundsIterator, SpecificFragmentInfo};
+use fragment::{Fragment, FragmentOverflowIterator, SpecificFragmentInfo};
 use incremental::{REFLOW, REFLOW_OUT_OF_FLOW};
 use layout_debug;
 use model::{IntrinsicISizes, MarginCollapseInfo};
@@ -49,7 +49,7 @@ use model::{MaybeAuto, CollapsibleMargins, specified, specified_or_none};
 use table::ColumnComputedInlineSize;
 use wrapper::ThreadSafeLayoutNode;
 
-use geom::Size2D;
+use geom::{Rect, Size2D};
 use gfx::display_list::{ClippingRegion, DisplayList};
 use serialize::{Encoder, Encodable};
 use servo_msg::compositor_msg::LayerId;
@@ -1797,13 +1797,6 @@ impl Flow for BlockFlow {
         self.flags.insert(IS_ROOT)
     }
 
-    /// Return true if store overflow is delayed for this flow.
-    ///
-    /// Currently happens only for absolutely positioned flows.
-    fn is_store_overflow_delayed(&mut self) -> bool {
-        self.base.flags.contains(IS_ABSOLUTELY_POSITIONED)
-    }
-
     fn is_root(&self) -> bool {
         self.flags.contains(IS_ROOT)
     }
@@ -1864,12 +1857,13 @@ impl Flow for BlockFlow {
         self.fragment.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.fragment.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
         if iterator.should_process(&self.fragment) {
-            let fragment_origin =
-                self.base.stacking_relative_position_of_child_fragment(&self.fragment);
-            iterator.process(&self.fragment,
-                             self.fragment.stacking_relative_bounds(&fragment_origin));
+            iterator.process(&self.fragment, self.fragment.compute_overflow());
         }
     }
 }
@@ -2455,11 +2449,14 @@ impl ISizeAndMarginsComputer for AbsoluteReplaced {
         MaybeAuto::Specified(fragment.content_inline_size())
     }
 
-    fn containing_block_inline_size(&self, block: &mut BlockFlow, _: Au, ctx: &LayoutContext) -> Au {
+    fn containing_block_inline_size(&self, block: &mut BlockFlow, _: Au, ctx: &LayoutContext)
+                                    -> Au {
         block.containing_block_size(ctx.shared.screen_size).inline
     }
 
-    fn set_flow_x_coord_if_necessary(&self, block: &mut BlockFlow, solution: ISizeConstraintSolution) {
+    fn set_flow_x_coord_if_necessary(&self,
+                                     block: &mut BlockFlow,
+                                     solution: ISizeConstraintSolution) {
         // Set the x-coordinate of the absolute flow wrt to its containing block.
         block.base.position.start.i = solution.inline_start;
     }
diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index a9ca6d5f547..2696bcc3dc5 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -1103,7 +1103,8 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
                                                background_border_level);
 
         self.base.display_list_building_result = if self.fragment.establishes_stacking_context() {
-            DisplayListBuildingResult::StackingContext(self.create_stacking_context(display_list, None))
+            DisplayListBuildingResult::StackingContext(self.create_stacking_context(display_list,
+                                                                                    None))
         } else {
             DisplayListBuildingResult::Normal(display_list)
         }
@@ -1120,7 +1121,9 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
                 !self.base.flags.contains(NEEDS_LAYER) {
             // We didn't need a layer.
             self.base.display_list_building_result =
-                DisplayListBuildingResult::StackingContext(self.create_stacking_context(display_list, None));
+                DisplayListBuildingResult::StackingContext(self.create_stacking_context(
+                        display_list,
+                        None));
             return
         }
 
@@ -1137,7 +1140,8 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
                                          Some(Arc::new(PaintLayer::new(self.layer_id(0),
                                                                        transparent,
                                                                        scroll_policy))));
-        self.base.display_list_building_result = DisplayListBuildingResult::StackingContext(stacking_context)
+        self.base.display_list_building_result =
+            DisplayListBuildingResult::StackingContext(stacking_context)
     }
 
     fn build_display_list_for_floating_block(&mut self,
@@ -1149,7 +1153,8 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
         display_list.form_float_pseudo_stacking_context();
 
         self.base.display_list_building_result = if self.fragment.establishes_stacking_context() {
-            DisplayListBuildingResult::StackingContext(self.create_stacking_context(display_list, None))
+            DisplayListBuildingResult::StackingContext(self.create_stacking_context(display_list,
+                                                                                    None))
         } else {
             DisplayListBuildingResult::Normal(display_list)
         }
@@ -1165,7 +1170,9 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
         } else if self.base.flags.contains(IS_ABSOLUTELY_POSITIONED) {
             self.build_display_list_for_absolutely_positioned_block(display_list, layout_context)
         } else {
-            self.build_display_list_for_static_block(display_list, layout_context, BackgroundAndBorderLevel::Block)
+            self.build_display_list_for_static_block(display_list,
+                                                     layout_context,
+                                                     BackgroundAndBorderLevel::Block)
         }
     }
 
@@ -1173,11 +1180,16 @@ impl BlockFlowDisplayListBuilding for BlockFlow {
                                display_list: Box<DisplayList>,
                                layer: Option<Arc<PaintLayer>>)
                                -> Arc<StackingContext> {
-        let bounds = Rect(self.base.stacking_relative_position,
-                          self.base.overflow.size.to_physical(self.base.writing_mode));
+        let size = self.base.position.size.to_physical(self.base.writing_mode);
+        let bounds = Rect(self.base.stacking_relative_position, size);
         let z_index = self.fragment.style().get_box().z_index.number_or_zero();
         let opacity = self.fragment.style().get_effects().opacity as f32;
-        Arc::new(StackingContext::new(display_list, bounds, z_index, opacity, layer))
+        Arc::new(StackingContext::new(display_list,
+                                      &bounds,
+                                      &self.base.overflow,
+                                      z_index,
+                                      opacity,
+                                      layer))
     }
 }
 
diff --git a/components/layout/flow.rs b/components/layout/flow.rs
index a36fca0df0a..f20d5a0c128 100644
--- a/components/layout/flow.rs
+++ b/components/layout/flow.rs
@@ -32,7 +32,7 @@ use display_list_builder::DisplayListBuildingResult;
 use floats::Floats;
 use flow_list::{FlowList, FlowListIterator, MutFlowListIterator};
 use flow_ref::FlowRef;
-use fragment::{Fragment, FragmentBoundsIterator, SpecificFragmentInfo};
+use fragment::{Fragment, FragmentOverflowIterator, SpecificFragmentInfo};
 use incremental::{RECONSTRUCT_FLOW, REFLOW, REFLOW_OUT_OF_FLOW, RestyleDamage};
 use inline::InlineFlow;
 use model::{CollapsibleMargins, IntrinsicISizes, MarginCollapseInfo};
@@ -50,7 +50,7 @@ use geom::{Point2D, Rect, Size2D};
 use gfx::display_list::ClippingRegion;
 use serialize::{Encoder, Encodable};
 use servo_msg::compositor_msg::LayerId;
-use servo_util::geometry::Au;
+use servo_util::geometry::{Au, ZERO_RECT};
 use servo_util::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
 use std::mem;
 use std::fmt;
@@ -220,8 +220,11 @@ pub trait Flow: fmt::Show + ToString + Sync {
     /// Phase 5 of reflow: builds display lists.
     fn build_display_list(&mut self, layout_context: &LayoutContext);
 
-    /// Perform an iteration of fragment bounds on this flow.
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator);
+    /// Returns the union of all overflow rects of all of this flow's fragments.
+    fn compute_overflow(&self) -> Rect<Au>;
+
+    /// Iterates through overflow rects of all of this flow's fragments.
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator);
 
     fn compute_collapsible_block_start_margin(&mut self,
                                               _layout_context: &mut LayoutContext,
@@ -718,7 +721,7 @@ pub struct BaseFlow {
 
     /// The amount of overflow of this flow, relative to the containing block. Must include all the
     /// pixels of all the display list items for correct invalidation.
-    pub overflow: LogicalRect<Au>,
+    pub overflow: Rect<Au>,
 
     /// Data used during parallel traversals.
     ///
@@ -894,7 +897,7 @@ impl BaseFlow {
             children: FlowList::new(),
             intrinsic_inline_sizes: IntrinsicISizes::new(),
             position: LogicalRect::zero(writing_mode),
-            overflow: LogicalRect::zero(writing_mode),
+            overflow: ZERO_RECT,
             parallel: FlowParallelInfo::new(),
             floats: Floats::new(writing_mode),
             collapsible_margins: CollapsibleMargins::new(),
@@ -929,10 +932,12 @@ impl BaseFlow {
     /// Ensures that all display list items generated by this flow are within the flow's overflow
     /// rect. This should only be used for debugging.
     pub fn validate_display_list_geometry(&self) {
-        let position_with_overflow = self.position.union(&self.overflow);
-        let bounds = Rect(self.stacking_relative_position,
-                          Size2D(position_with_overflow.size.inline,
-                                 position_with_overflow.size.block));
+        // FIXME(pcwalton, #2795): Get the real container size.
+        let container_size = Size2D::zero();
+        let position_with_overflow = self.position
+                                         .to_physical(self.writing_mode, container_size)
+                                         .union(&self.overflow);
+        let bounds = Rect(self.stacking_relative_position, position_with_overflow.size);
 
         let all_items = match self.display_list_building_result {
             DisplayListBuildingResult::None => Vec::new(),
@@ -1175,40 +1180,29 @@ impl<'a> MutableFlowUtils for &'a mut Flow + 'a {
     /// already been set.
     /// Assumption: Absolute descendants have had their overflow calculated.
     fn store_overflow(self, _: &LayoutContext) {
-        let my_position = mut_base(self).position;
-
-        // FIXME(pcwalton): We should calculate overflow on a per-fragment basis, because their
-        // styles can affect overflow regions. Consider `box-shadow`, `outline`, etc.--anything
-        // that can draw outside the border box. For now we assume overflow is the border box, but
-        // that is wrong.
-        let mut overflow = my_position;
-
+        // Calculate overflow on a per-fragment basis.
+        let mut overflow = self.compute_overflow();
         if self.is_block_container() {
-            let writing_mode = base(self).writing_mode;
-            // FIXME(#2795): Get the real container size
+            // FIXME(#2795): Get the real container size.
             let container_size = Size2D::zero();
             for kid in child_iter(self) {
-                if kid.is_store_overflow_delayed() {
-                    // Absolute flows will be handled by their CB. If we are
-                    // their CB, they will show up in `abs_descendants`.
-                    continue;
+                if base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
+                    continue
                 }
-                let kid_base = base(kid);
-                let mut kid_overflow = kid_base.overflow.convert(
-                    kid_base.writing_mode, writing_mode, container_size);
-                kid_overflow = kid_overflow.translate(&my_position.start);
-                overflow = overflow.union(&kid_overflow)
+                let kid_overflow = base(kid).overflow;
+                let kid_position = base(kid).position.to_physical(base(kid).writing_mode,
+                                                                  container_size);
+                overflow = overflow.union(&kid_overflow.translate(&kid_position.origin))
             }
 
-            // FIXME(#2004, pcwalton): This is wrong for `position: fixed`.
-            for descendant_link in mut_base(self).abs_descendants.iter() {
-                let kid_base = base(descendant_link);
-                let mut kid_overflow = kid_base.overflow.convert(
-                    kid_base.writing_mode, writing_mode, container_size);
-                kid_overflow = kid_overflow.translate(&my_position.start);
-                overflow = overflow.union(&kid_overflow)
+            for kid in mut_base(self).abs_descendants.iter() {
+                let kid_overflow = base(kid).overflow;
+                let kid_position = base(kid).position.to_physical(base(kid).writing_mode,
+                                                                  container_size);
+                overflow = overflow.union(&kid_overflow.translate(&kid_position.origin))
             }
         }
+
         mut_base(self).overflow = overflow;
     }
 
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index b50f484f8d9..c66087364ed 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -23,7 +23,7 @@ use util::OpaqueNodeMethods;
 use wrapper::{TLayoutNode, ThreadSafeLayoutNode};
 
 use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::OpaqueNode;
+use gfx::display_list::{BOX_SHADOW_INFLATION_FACTOR, OpaqueNode};
 use gfx::text::glyph::CharIndex;
 use gfx::text::text_run::{TextRun, TextRunSlice};
 use script_traits::UntrustedNodeAddress;
@@ -531,8 +531,9 @@ impl Fragment {
         //         Foo
         //     </div>
         //
-        // Anonymous table fragments, SpecificFragmentInfo::TableRow and SpecificFragmentInfo::TableCell, are generated around
-        // `Foo`, but they shouldn't inherit the border.
+        // Anonymous table fragments, SpecificFragmentInfo::TableRow and
+        // SpecificFragmentInfo::TableCell, are generated around `Foo`, but they shouldn't inherit
+        // the border.
 
         let node_style = cascade_anonymous(&**node.style());
         let writing_mode = node_style.writing_mode;
@@ -647,7 +648,10 @@ impl Fragment {
     fn quantities_included_in_intrinsic_inline_size(&self)
                                                     -> QuantitiesIncludedInIntrinsicInlineSizes {
         match self.specific {
-            SpecificFragmentInfo::Generic | SpecificFragmentInfo::Iframe(_) | SpecificFragmentInfo::Image(_) | SpecificFragmentInfo::InlineBlock(_) => {
+            SpecificFragmentInfo::Generic |
+            SpecificFragmentInfo::Iframe(_) |
+            SpecificFragmentInfo::Image(_) |
+            SpecificFragmentInfo::InlineBlock(_) => {
                 QuantitiesIncludedInIntrinsicInlineSizes::all()
             }
             SpecificFragmentInfo::Table | SpecificFragmentInfo::TableCell => {
@@ -836,9 +840,7 @@ impl Fragment {
     }
 
     // Return offset from original position because of `position: relative`.
-    pub fn relative_position(&self,
-                             containing_block_size: &LogicalSize<Au>)
-                             -> LogicalSize<Au> {
+    pub fn relative_position(&self, containing_block_size: &LogicalSize<Au>) -> LogicalSize<Au> {
         fn from_style(style: &ComputedValues, container_size: &LogicalSize<Au>)
                       -> LogicalSize<Au> {
             let offsets = style.logical_position();
@@ -1567,6 +1569,41 @@ impl Fragment {
             }
         }
     }
+
+    /// Computes the overflow rect of this fragment relative to the start of the flow.
+    pub fn compute_overflow(&self) -> Rect<Au> {
+        // FIXME(pcwalton, #2795): Get the real container size.
+        let container_size = Size2D::zero();
+        let mut border_box = self.border_box.to_physical(self.style.writing_mode, container_size);
+
+        // Relative position can cause us to draw outside our border box.
+        //
+        // FIXME(pcwalton): I'm not a fan of the way this makes us crawl though so many styles all
+        // the time. Can't we handle relative positioning by just adjusting `border_box`?
+        let relative_position =
+            self.relative_position(&LogicalSize::zero(self.style.writing_mode));
+        border_box =
+            border_box.translate_by_size(&relative_position.to_physical(self.style.writing_mode));
+        let mut overflow = border_box;
+
+        // Box shadows cause us to draw outside our border box.
+        for box_shadow in self.style().get_effects().box_shadow.iter() {
+            let offset = Point2D(box_shadow.offset_x, box_shadow.offset_y);
+            let inflation = box_shadow.spread_radius +
+                box_shadow.blur_radius * BOX_SHADOW_INFLATION_FACTOR;
+            overflow = overflow.union(&border_box.translate(&offset).inflate(inflation, inflation))
+        }
+
+        // Outlines cause us to draw outside our border box.
+        let outline_width = self.style.get_outline().outline_width;
+        if outline_width != Au(0) {
+            overflow = overflow.union(&border_box.inflate(outline_width, outline_width))
+        }
+
+        // FIXME(pcwalton): Sometimes excessively fancy glyphs can make us draw outside our border
+        // box too.
+        overflow
+    }
 }
 
 impl fmt::Show for Fragment {
@@ -1600,10 +1637,10 @@ bitflags! {
     }
 }
 
-/// A top-down fragment bounds iteration handler.
-pub trait FragmentBoundsIterator {
+/// A top-down fragment overflow region iteration handler.
+pub trait FragmentOverflowIterator {
     /// The operation to perform.
-    fn process(&mut self, fragment: &Fragment, bounds: Rect<Au>);
+    fn process(&mut self, fragment: &Fragment, overflow: Rect<Au>);
 
     /// Returns true if this fragment must be processed in-order. If this returns false,
     /// we skip the operation for this fragment, but continue processing siblings.
diff --git a/components/layout/inline.rs b/components/layout/inline.rs
index 2230fb3e823..f8a19708d1e 100644
--- a/components/layout/inline.rs
+++ b/components/layout/inline.rs
@@ -12,7 +12,7 @@ use flow::{BaseFlow, FlowClass, Flow, MutableFlowUtils, ForceNonfloatedFlag};
 use flow::{IS_ABSOLUTELY_POSITIONED};
 use flow;
 use fragment::{Fragment, SpecificFragmentInfo};
-use fragment::{FragmentBoundsIterator, ScannedTextFragmentInfo};
+use fragment::{FragmentOverflowIterator, ScannedTextFragmentInfo};
 use fragment::SplitInfo;
 use incremental::{REFLOW, REFLOW_OUT_OF_FLOW};
 use layout_debug;
@@ -20,12 +20,12 @@ use model::IntrinsicISizesContribution;
 use text;
 
 use collections::{RingBuf};
-use geom::Size2D;
+use geom::{Rect, Size2D};
 use gfx::display_list::DisplayList;
 use gfx::font::FontMetrics;
 use gfx::font_context::FontContext;
 use gfx::text::glyph::CharIndex;
-use servo_util::geometry::Au;
+use servo_util::geometry::{Au, ZERO_RECT};
 use servo_util::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
 use servo_util::opts;
 use servo_util::range::{Range, RangeIndex};
@@ -1271,7 +1271,15 @@ impl Flow for InlineFlow {
 
     fn repair_style(&mut self, _: &Arc<ComputedValues>) {}
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
+    fn compute_overflow(&self) -> Rect<Au> {
+        let mut overflow = ZERO_RECT;
+        for fragment in self.fragments.fragments.iter() {
+            overflow = overflow.union(&fragment.compute_overflow())
+        }
+        overflow
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
         for fragment in self.fragments.fragments.iter() {
             if iterator.should_process(fragment) {
                 let fragment_origin =
diff --git a/components/layout/layout_task.rs b/components/layout/layout_task.rs
index 090b51cee70..22e00904c75 100644
--- a/components/layout/layout_task.rs
+++ b/components/layout/layout_task.rs
@@ -10,7 +10,7 @@ use construct::ConstructionResult;
 use context::SharedLayoutContext;
 use flow::{mod, Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
 use flow_ref::FlowRef;
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use incremental::{LayoutDamageComputation, REFLOW, REFLOW_ENTIRE_DOCUMENT, REPAINT};
 use layout_debug;
 use parallel::{mod, UnsafeFlow};
@@ -604,7 +604,7 @@ impl LayoutTask {
         // FIXME(pcwalton): This has not been updated to handle the stacking context relative
         // stuff. So the position is wrong in most cases.
         let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node);
-        let mut iterator = UnioningFragmentBoundsIterator::new(requested_node);
+        let mut iterator = UnioningFragmentOverflowIterator::new(requested_node);
         sequential::iterate_through_flow_tree_fragment_bounds(layout_root, &mut iterator);
         rw_data.content_box_response = iterator.rect;
     }
@@ -616,7 +616,7 @@ impl LayoutTask {
         // FIXME(pcwalton): This has not been updated to handle the stacking context relative
         // stuff. So the position is wrong in most cases.
         let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node);
-        let mut iterator = CollectingFragmentBoundsIterator::new(requested_node);
+        let mut iterator = CollectingFragmentOverflowIterator::new(requested_node);
         sequential::iterate_through_flow_tree_fragment_bounds(layout_root, &mut iterator);
         rw_data.content_boxes_response = iterator.rects;
     }
@@ -689,11 +689,12 @@ impl LayoutTask {
             flow::mut_base(layout_root.deref_mut()).display_list_building_result
                                                    .add_to(&mut *display_list);
             let paint_layer = Arc::new(PaintLayer::new(layout_root.layer_id(0),
-                                                         color,
-                                                         Scrollable));
+                                                       color,
+                                                       Scrollable));
             let origin = Rect(Point2D(Au(0), Au(0)), root_size);
             let stacking_context = Arc::new(StackingContext::new(display_list,
-                                                                 origin,
+                                                                 &origin,
+                                                                 &origin,
                                                                  0,
                                                                  1.0,
                                                                  Some(paint_layer)));
@@ -1016,21 +1017,21 @@ impl LayoutRPC for LayoutRPCImpl {
     }
 }
 
-struct UnioningFragmentBoundsIterator {
+struct UnioningFragmentOverflowIterator {
     node_address: OpaqueNode,
     rect: Rect<Au>,
 }
 
-impl UnioningFragmentBoundsIterator {
-    fn new(node_address: OpaqueNode) -> UnioningFragmentBoundsIterator {
-        UnioningFragmentBoundsIterator {
+impl UnioningFragmentOverflowIterator {
+    fn new(node_address: OpaqueNode) -> UnioningFragmentOverflowIterator {
+        UnioningFragmentOverflowIterator {
             node_address: node_address,
             rect: Rect::zero(),
         }
     }
 }
 
-impl FragmentBoundsIterator for UnioningFragmentBoundsIterator {
+impl FragmentOverflowIterator for UnioningFragmentOverflowIterator {
     fn process(&mut self, _: &Fragment, bounds: Rect<Au>) {
         if self.rect.is_empty() {
             self.rect = bounds;
@@ -1044,21 +1045,21 @@ impl FragmentBoundsIterator for UnioningFragmentBoundsIterator {
     }
 }
 
-struct CollectingFragmentBoundsIterator {
+struct CollectingFragmentOverflowIterator {
     node_address: OpaqueNode,
     rects: Vec<Rect<Au>>,
 }
 
-impl CollectingFragmentBoundsIterator {
-    fn new(node_address: OpaqueNode) -> CollectingFragmentBoundsIterator {
-        CollectingFragmentBoundsIterator {
+impl CollectingFragmentOverflowIterator {
+    fn new(node_address: OpaqueNode) -> CollectingFragmentOverflowIterator {
+        CollectingFragmentOverflowIterator {
             node_address: node_address,
             rects: Vec::new(),
         }
     }
 }
 
-impl FragmentBoundsIterator for CollectingFragmentBoundsIterator {
+impl FragmentOverflowIterator for CollectingFragmentOverflowIterator {
     fn process(&mut self, _: &Fragment, bounds: Rect<Au>) {
         self.rects.push(bounds);
     }
diff --git a/components/layout/list_item.rs b/components/layout/list_item.rs
index 3b31d1fdc44..0d0c71d526c 100644
--- a/components/layout/list_item.rs
+++ b/components/layout/list_item.rs
@@ -12,9 +12,10 @@ use construct::FlowConstructor;
 use context::LayoutContext;
 use display_list_builder::ListItemFlowDisplayListBuilding;
 use flow::{Flow, FlowClass};
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use gfx::display_list::DisplayList;
 use servo_util::geometry::Au;
 use servo_util::opts;
@@ -111,8 +112,12 @@ impl Flow for ListItemFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/sequential.rs b/components/layout/sequential.rs
index 4636fa9c3eb..01ba0c098ed 100644
--- a/components/layout/sequential.rs
+++ b/components/layout/sequential.rs
@@ -8,7 +8,7 @@ use context::{LayoutContext, SharedLayoutContext};
 use flow::{Flow, MutableFlowUtils, PreorderFlowTraversal, PostorderFlowTraversal};
 use flow;
 use flow_ref::FlowRef;
-use fragment::FragmentBoundsIterator;
+use fragment::FragmentOverflowIterator;
 use servo_util::opts;
 use traversal::{BubbleISizes, RecalcStyleForNode, ConstructFlows};
 use traversal::{AssignBSizesAndStoreOverflow, AssignISizes};
@@ -95,9 +95,9 @@ pub fn build_display_list_for_subtree(root: &mut FlowRef,
 }
 
 pub fn iterate_through_flow_tree_fragment_bounds(root: &mut FlowRef,
-                                                 iterator: &mut FragmentBoundsIterator) {
-    fn doit(flow: &mut Flow, iterator: &mut FragmentBoundsIterator) {
-        flow.iterate_through_fragment_bounds(iterator);
+                                                 iterator: &mut FragmentOverflowIterator) {
+    fn doit(flow: &mut Flow, iterator: &mut FragmentOverflowIterator) {
+        flow.iterate_through_fragment_overflow(iterator);
 
         for kid in flow::mut_base(flow).child_iter() {
             doit(kid, iterator);
diff --git a/components/layout/table.rs b/components/layout/table.rs
index 8f46ef868ff..81c9f40d43d 100644
--- a/components/layout/table.rs
+++ b/components/layout/table.rs
@@ -13,13 +13,14 @@ use context::LayoutContext;
 use floats::FloatKind;
 use flow::{mod, Flow, FlowClass, IMPACTED_BY_LEFT_FLOATS, IMPACTED_BY_RIGHT_FLOATS};
 use flow::ImmutableFlowUtils;
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use layout_debug;
 use model::{IntrinsicISizes, IntrinsicISizesContribution};
 use table_row::CellIntrinsicInlineSize;
 use table_wrapper::TableLayout;
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use servo_util::logical_geometry::LogicalRect;
 use std::cmp::max;
@@ -384,8 +385,12 @@ impl Flow for TableFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/table_caption.rs b/components/layout/table_caption.rs
index 65493e2c24a..4864e49096a 100644
--- a/components/layout/table_caption.rs
+++ b/components/layout/table_caption.rs
@@ -10,9 +10,10 @@ use block::BlockFlow;
 use construct::FlowConstructor;
 use context::LayoutContext;
 use flow::{FlowClass, Flow};
-use fragment::FragmentBoundsIterator;
+use fragment::FragmentOverflowIterator;
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use std::fmt;
 use style::ComputedValues;
@@ -81,8 +82,12 @@ impl Flow for TableCaptionFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/table_cell.rs b/components/layout/table_cell.rs
index 3d1f1fd54e3..583c328f315 100644
--- a/components/layout/table_cell.rs
+++ b/components/layout/table_cell.rs
@@ -9,12 +9,13 @@
 use block::{BlockFlow, ISizeAndMarginsComputer, MarginsMayCollapseFlag};
 use context::LayoutContext;
 use flow::{Flow, FlowClass};
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use model::{MaybeAuto};
 use layout_debug;
 use table::InternalTable;
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use std::fmt;
 use style::{UnsignedIntegerAttribute, ComputedValues};
@@ -162,8 +163,12 @@ impl Flow for TableCellFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/table_colgroup.rs b/components/layout/table_colgroup.rs
index 5ce9f559268..4eb1cae8022 100644
--- a/components/layout/table_colgroup.rs
+++ b/components/layout/table_colgroup.rs
@@ -9,11 +9,12 @@
 use context::LayoutContext;
 use css::node_style::StyledNode;
 use flow::{BaseFlow, FlowClass, Flow, ForceNonfloatedFlag};
-use fragment::{Fragment, FragmentBoundsIterator, SpecificFragmentInfo};
+use fragment::{Fragment, FragmentOverflowIterator, SpecificFragmentInfo};
 use layout_debug;
 use wrapper::ThreadSafeLayoutNode;
 
-use servo_util::geometry::Au;
+use geom::Rect;
+use servo_util::geometry::{Au, ZERO_RECT};
 use std::cmp::max;
 use std::fmt;
 use style::computed_values::LengthOrPercentageOrAuto;
@@ -96,7 +97,11 @@ impl Flow for TableColGroupFlow {
 
     fn repair_style(&mut self, _: &Arc<ComputedValues>) {}
 
-    fn iterate_through_fragment_bounds(&self, _: &mut FragmentBoundsIterator) {
+    fn compute_overflow(&self) -> Rect<Au> {
+        ZERO_RECT
+    }
+
+    fn iterate_through_fragment_overflow(&self, _: &mut FragmentOverflowIterator) {
     }
 }
 
diff --git a/components/layout/table_row.rs b/components/layout/table_row.rs
index d4979de8800..d27d7d1ffb4 100644
--- a/components/layout/table_row.rs
+++ b/components/layout/table_row.rs
@@ -12,12 +12,13 @@ use construct::FlowConstructor;
 use context::LayoutContext;
 use flow::{FlowClass, Flow, ImmutableFlowUtils};
 use flow;
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use layout_debug;
 use table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize, InternalTable};
 use model::MaybeAuto;
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use std::cmp::max;
 use std::fmt;
@@ -315,8 +316,12 @@ impl Flow for TableRowFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/table_rowgroup.rs b/components/layout/table_rowgroup.rs
index e004890c53d..5d3673c1612 100644
--- a/components/layout/table_rowgroup.rs
+++ b/components/layout/table_rowgroup.rs
@@ -10,11 +10,12 @@ use block::{BlockFlow, ISizeAndMarginsComputer, MarginsMayCollapseFlag};
 use construct::FlowConstructor;
 use context::LayoutContext;
 use flow::{FlowClass, Flow};
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use layout_debug;
 use table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize, InternalTable};
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use std::fmt;
 use style::ComputedValues;
@@ -150,8 +151,12 @@ impl Flow for TableRowGroupFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/table_wrapper.rs b/components/layout/table_wrapper.rs
index e3d6433a36f..fa8497c46d7 100644
--- a/components/layout/table_wrapper.rs
+++ b/components/layout/table_wrapper.rs
@@ -19,10 +19,11 @@ use context::LayoutContext;
 use floats::FloatKind;
 use flow::{FlowClass, Flow, ImmutableFlowUtils};
 use flow::{IMPACTED_BY_LEFT_FLOATS, IMPACTED_BY_RIGHT_FLOATS};
-use fragment::{Fragment, FragmentBoundsIterator};
+use fragment::{Fragment, FragmentOverflowIterator};
 use table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize};
 use wrapper::ThreadSafeLayoutNode;
 
+use geom::Rect;
 use servo_util::geometry::Au;
 use std::cmp::{max, min};
 use std::fmt;
@@ -358,8 +359,12 @@ impl Flow for TableWrapperFlow {
         self.block_flow.repair_style(new_style)
     }
 
-    fn iterate_through_fragment_bounds(&self, iterator: &mut FragmentBoundsIterator) {
-        self.block_flow.iterate_through_fragment_bounds(iterator);
+    fn compute_overflow(&self) -> Rect<Au> {
+        self.block_flow.compute_overflow()
+    }
+
+    fn iterate_through_fragment_overflow(&self, iterator: &mut FragmentOverflowIterator) {
+        self.block_flow.iterate_through_fragment_overflow(iterator);
     }
 }
 
diff --git a/components/layout/traversal.rs b/components/layout/traversal.rs
index 4b824160902..df56254c066 100644
--- a/components/layout/traversal.rs
+++ b/components/layout/traversal.rs
@@ -332,12 +332,7 @@ impl<'a> PostorderFlowTraversal for AssignBSizesAndStoreOverflow<'a> {
         }
 
         flow.assign_block_size(self.layout_context);
-
-        // Skip store-overflow for absolutely positioned flows. That will be
-        // done in a separate traversal.
-        if !flow.is_store_overflow_delayed() {
-            flow.store_overflow(self.layout_context);
-        }
+        flow.store_overflow(self.layout_context);
     }
 
     #[inline]
diff --git a/components/msg/compositor_msg.rs b/components/msg/compositor_msg.rs
index 284e40b53af..9d280cef673 100644
--- a/components/msg/compositor_msg.rs
+++ b/components/msg/compositor_msg.rs
@@ -75,7 +75,7 @@ pub struct LayerMetadata {
     /// An opaque ID. This is usually the address of the flow and index of the box within it.
     pub id: LayerId,
     /// The position and size of the layer in pixels.
-    pub position: Rect<uint>,
+    pub position: Rect<i32>,
     /// The background color of the layer.
     pub background_color: Color,
     /// The scrolling policy of this layer.
diff --git a/components/servo/Cargo.lock b/components/servo/Cargo.lock
index e3662c1a3c4..b92f7ea77ce 100644
--- a/components/servo/Cargo.lock
+++ b/components/servo/Cargo.lock
@@ -248,7 +248,7 @@ source = "git+https://github.com/alexcrichton/gcc-rs#903e8f8a2e3766ad3d514404d45
 [[package]]
 name = "geom"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-geom#da6b4a36a5549cf78bf702f0b9387b5c8cf61498"
+source = "git+https://github.com/servo/rust-geom#0f77c6ad116748b7e6bedbf2414d4ceea17debc2"
 
 [[package]]
 name = "gfx"
diff --git a/ports/cef/Cargo.lock b/ports/cef/Cargo.lock
index 3ebeef17673..e203988b28b 100644
--- a/ports/cef/Cargo.lock
+++ b/ports/cef/Cargo.lock
@@ -244,7 +244,7 @@ source = "git+https://github.com/alexcrichton/gcc-rs#903e8f8a2e3766ad3d514404d45
 [[package]]
 name = "geom"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-geom#da6b4a36a5549cf78bf702f0b9387b5c8cf61498"
+source = "git+https://github.com/servo/rust-geom#0f77c6ad116748b7e6bedbf2414d4ceea17debc2"
 
 [[package]]
 name = "gfx"
diff --git a/ports/gonk/Cargo.lock b/ports/gonk/Cargo.lock
index 19641c7399c..6be4f9e4535 100644
--- a/ports/gonk/Cargo.lock
+++ b/ports/gonk/Cargo.lock
@@ -227,7 +227,7 @@ source = "git+https://github.com/alexcrichton/gcc-rs#903e8f8a2e3766ad3d514404d45
 [[package]]
 name = "geom"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-geom#da6b4a36a5549cf78bf702f0b9387b5c8cf61498"
+source = "git+https://github.com/servo/rust-geom#0f77c6ad116748b7e6bedbf2414d4ceea17debc2"
 
 [[package]]
 name = "gfx"
diff --git a/tests/ref/basic.list b/tests/ref/basic.list
index 29ad0825f00..67e6300969f 100644
--- a/tests/ref/basic.list
+++ b/tests/ref/basic.list
@@ -222,3 +222,5 @@ fragment=top != ../html/acid2.html acid2_ref.html
 != inset_blackborder.html blackborder_ref.html
 != outset_blackborder.html blackborder_ref.html
 == border_radius_clip_a.html border_radius_clip_ref.html
+== stacking_context_overflow_a.html stacking_context_overflow_ref.html
+== stacking_context_overflow_relative_outline_a.html stacking_context_overflow_relative_outline_ref.html
diff --git a/tests/ref/position_fixed_tile_edge_3.html b/tests/ref/position_fixed_tile_edge_3.html
index dcf2341c170..60e20fb22b0 100644
--- a/tests/ref/position_fixed_tile_edge_3.html
+++ b/tests/ref/position_fixed_tile_edge_3.html
@@ -1,7 +1,7 @@
 <html>
   <body>
     <div style="position: absolute; top: 0px; left: 0px;">
-        <div style="position: absolute; background: green; margin-left: 512px; width: 20px; height: 20px;"></div>
+        <div style="position: absolute; background: green; top: 0; margin-left: 512px; width: 20px; height: 20px;"></div>
 
         <!-- This position:fixed sibling should force its sibling to be layerized. -->
         <div style="position: fixed;"></div>
diff --git a/tests/ref/stacking_context_overflow_a.html b/tests/ref/stacking_context_overflow_a.html
new file mode 100644
index 00000000000..ea87a5dba55
--- /dev/null
+++ b/tests/ref/stacking_context_overflow_a.html
@@ -0,0 +1,22 @@
+<html>
+<head>
+<!-- Tests that stacking contexts display overflow. -->
+<style>
+body {
+    margin: 0;
+}
+section {
+    position: absolute;
+    z-index: 1;
+    width: 72px;
+    height: 72px;
+    border: solid black 2px;
+    font: 24px Arial;
+}
+</style>
+</head>
+<body>
+<section>CSS IS AWESOME</section>
+</body>
+</html>
+
diff --git a/tests/ref/stacking_context_overflow_ref.html b/tests/ref/stacking_context_overflow_ref.html
new file mode 100644
index 00000000000..49991c449ab
--- /dev/null
+++ b/tests/ref/stacking_context_overflow_ref.html
@@ -0,0 +1,21 @@
+<html>
+<head>
+<!-- Tests that stacking contexts display overflow. -->
+<style>
+body {
+    margin: 0;
+}
+section {
+    width: 72px;
+    height: 72px;
+    border: solid black 2px;
+    font: 24px Arial;
+}
+</style>
+</head>
+<body>
+<section>CSS IS AWESOME</section>
+</body>
+</html>
+
+
diff --git a/tests/ref/stacking_context_overflow_relative_outline_a.html b/tests/ref/stacking_context_overflow_relative_outline_a.html
new file mode 100644
index 00000000000..64b965063fc
--- /dev/null
+++ b/tests/ref/stacking_context_overflow_relative_outline_a.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<style>
+section {
+    position: absolute;
+    top: 100px;
+    left: 100px;
+    width: 10px;
+    height: 10px;
+}
+h1 {
+    position: relative;
+    top: -50px;
+    left: -50px;
+    width: 200px;
+    height: 200px;
+    margin: 0;
+    outline: solid 10px green;
+}
+</style>
+<body>
+<section><h1></h1></section>
+</body>
+</html>
+
diff --git a/tests/ref/stacking_context_overflow_relative_outline_ref.html b/tests/ref/stacking_context_overflow_relative_outline_ref.html
new file mode 100644
index 00000000000..6117d76ff8f
--- /dev/null
+++ b/tests/ref/stacking_context_overflow_relative_outline_ref.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+<style>
+section {
+    position: absolute;
+    top: 40px;
+    left: 40px;
+    width: 200px;
+    height: 200px;
+    border: solid 10px green;
+}
+</style>
+<body>
+<section></section>
+</body>
+</html>
+
+