Change overflow calculation to be calculated after compute_absolute_position.

Also include absolutely positioned elements in the overflow rect calculation.

Fixes #7797.

10 files changed, 75 insertions, 105 deletions

diff --git a/components/layout/block.rs b/components/layout/block.rs
index 399b3e5a9f4..06b003862b4 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -42,7 +42,6 @@ use flow::{ImmutableFlowUtils, LateAbsolutePositionInfo, MutableFlowUtils, Opaqu
 use flow::{LAYERS_NEEDED_FOR_DESCENDANTS, NEEDS_LAYER};
 use flow::{PostorderFlowTraversal, PreorderFlowTraversal, mut_base};
 use flow::{self, BaseFlow, EarlyAbsolutePositionInfo, Flow, FlowClass, ForceNonfloatedFlag};
-use flow_ref;
 use fragment::{CoordinateSystem, Fragment, FragmentBorderBoxIterator, HAS_LAYER};
 use fragment::{SpecificFragmentInfo};
 use gfx::display_list::{ClippingRegion, DisplayList};
@@ -478,45 +477,6 @@ impl<'a> PreorderFlowTraversal for AbsoluteAssignBSizesTraversal<'a> {
     }
 }
 
-/// The store-overflow traversal particular to absolute flows.
-///
-/// Propagate overflow up the Absolute flow tree and update overflow up to and
-/// not including the root of the Absolute flow tree.
-/// After that, it is up to the normal store-overflow traversal to propagate
-/// it further up.
-pub struct AbsoluteStoreOverflowTraversal<'a>{
-    pub layout_context: &'a LayoutContext<'a>,
-}
-
-impl<'a> PostorderFlowTraversal for AbsoluteStoreOverflowTraversal<'a> {
-    #[inline]
-    fn process(&self, flow: &mut Flow) {
-        {
-            // This will be taken care of by the normal store-overflow traversal.
-            let flow: &Flow = flow;
-            if flow.contains_roots_of_absolute_flow_tree() {
-                return;
-            }
-        }
-
-        flow.mutate_fragments(&mut |f: &mut Fragment| {
-            match f.specific {
-                SpecificFragmentInfo::InlineBlock(ref mut info) => {
-                    let block = flow_ref::deref_mut(&mut info.flow_ref);
-                    (block.as_mut_block() as &mut Flow).early_store_overflow(self.layout_context);
-                }
-                SpecificFragmentInfo::InlineAbsolute(ref mut info) => {
-                    let block = flow_ref::deref_mut(&mut info.flow_ref);
-                    (block.as_mut_block() as &mut Flow).early_store_overflow(self.layout_context);
-                }
-                _ => (),
-            }
-        });
-
-        flow.early_store_overflow(self.layout_context);
-    }
-}
-
 pub enum BlockType {
     Replaced,
     NonReplaced,
@@ -1016,7 +976,6 @@ impl BlockFlow {
                     relative_containing_block_size: self.fragment.content_box().size,
                     relative_containing_block_mode: self.fragment.style().writing_mode,
                 };
-                kid.late_store_overflow(layout_context)
             }
 
             if self.base.flags.contains(IS_ABSOLUTELY_POSITIONED) {
@@ -1073,11 +1032,6 @@ impl BlockFlow {
             // the block-size of its containing block, which may also be an absolute flow.
             (&mut *self as &mut Flow).traverse_preorder_absolute_flows(
                 &mut AbsoluteAssignBSizesTraversal(layout_context));
-            // Store overflow for all absolute descendants.
-            (&mut *self as &mut Flow).traverse_postorder_absolute_flows(
-                &mut AbsoluteStoreOverflowTraversal {
-                    layout_context: layout_context,
-                });
         }
 
         // Don't remove the dirty bits yet if we're absolutely-positioned, since our final size
@@ -1795,7 +1749,6 @@ impl Flow for BlockFlow {
             self.base.thread_id = parent_thread_id;
             if self.base.restyle_damage.intersects(REFLOW_OUT_OF_FLOW | REFLOW) {
                 self.assign_block_size(layout_context);
-                (self as &mut Flow).early_store_overflow(layout_context);
                 // Don't remove the restyle damage; `assign_block_size` decides whether that is
                 // appropriate (which in the case of e.g. absolutely-positioned flows, it is not).
             }
diff --git a/components/layout/flow.rs b/components/layout/flow.rs
index 5be4533dc6a..baaf450e92b 100644
--- a/components/layout/flow.rs
+++ b/components/layout/flow.rs
@@ -220,11 +220,6 @@ pub trait Flow: fmt::Debug + Sync + Send + 'static {
         if impacted {
             mut_base(self).thread_id = parent_thread_id;
             self.assign_block_size(layout_context);
-            // FIXME(pcwalton): Should use `early_store_overflow()` here but that fails due to a
-            // compiler bug (`Self` does not have a constant size).
-            if !self.contains_relatively_positioned_fragments() {
-                self.store_overflow(layout_context)
-            }
             mut_base(self).restyle_damage.remove(REFLOW_OUT_OF_FLOW | REFLOW);
         }
         impacted
@@ -252,9 +247,6 @@ pub trait Flow: fmt::Debug + Sync + Send + 'static {
                 // FIXME(#2795): Get the real container size.
                 let container_size = Size2D::zero();
                 for kid in mut_base(self).children.iter_mut() {
-                    if base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
-                        continue
-                    }
                     let kid_overflow = base(kid).overflow;
                     let kid_position = base(kid).position.to_physical(base(kid).writing_mode,
                                                                       container_size);
@@ -461,11 +453,6 @@ pub trait ImmutableFlowUtils {
     /// Returns true if this flow is an inline flow.
     fn is_inline_flow(self) -> bool;
 
-    /// Returns true if this flow can have its overflow area calculated early (during its
-    /// block-size assignment) or false if it must have its overflow area calculated late (during
-    /// its parent's block-size assignment).
-    fn can_calculate_overflow_area_early(self) -> bool;
-
     /// Dumps the flow tree for debugging.
     fn dump(self);
 
@@ -502,12 +489,6 @@ pub trait MutableFlowUtils {
     /// Calls `repair_style` and `bubble_inline_sizes`. You should use this method instead of
     /// calling them individually, since there is no reason not to perform both operations.
     fn repair_style_and_bubble_inline_sizes(self, style: &Arc<ComputedValues>);
-
-    /// Calls `store_overflow()` if the overflow can be calculated early.
-    fn early_store_overflow(self, layout_context: &LayoutContext);
-
-    /// Calls `store_overflow()` if the overflow cannot be calculated early.
-    fn late_store_overflow(self, layout_context: &LayoutContext);
 }
 
 pub trait MutableOwnedFlowUtils {
@@ -1310,13 +1291,6 @@ impl<'a> ImmutableFlowUtils for &'a Flow {
         }
     }
 
-    /// Returns true if this flow can have its overflow area calculated early (during its
-    /// block-size assignment) or false if it must have its overflow area calculated late (during
-    /// its parent's block-size assignment).
-    fn can_calculate_overflow_area_early(self) -> bool {
-        !self.contains_relatively_positioned_fragments()
-    }
-
     /// Dumps the flow tree for debugging.
     fn dump(self) {
         self.dump_with_level(0)
@@ -1395,20 +1369,6 @@ impl<'a> MutableFlowUtils for &'a mut Flow {
 
         traversal.process(*self)
     }
-
-    /// Calls `store_overflow()` if the overflow can be calculated early.
-    fn early_store_overflow(self, layout_context: &LayoutContext) {
-        if self.can_calculate_overflow_area_early() {
-            self.store_overflow(layout_context)
-        }
-    }
-
-    /// Calls `store_overflow()` if the overflow cannot be calculated early.
-    fn late_store_overflow(self, layout_context: &LayoutContext) {
-        if !self.can_calculate_overflow_area_early() {
-            self.store_overflow(layout_context)
-        }
-    }
 }
 
 impl MutableOwnedFlowUtils for FlowRef {
diff --git a/components/layout/inline.rs b/components/layout/inline.rs
index 8711881ffaf..fe798496e11 100644
--- a/components/layout/inline.rs
+++ b/components/layout/inline.rs
@@ -5,7 +5,7 @@
 #![deny(unsafe_code)]
 
 use app_units::Au;
-use block::{AbsoluteAssignBSizesTraversal, AbsoluteStoreOverflowTraversal};
+use block::AbsoluteAssignBSizesTraversal;
 use context::LayoutContext;
 use display_list_builder::{FragmentDisplayListBuilding, InlineFlowDisplayListBuilding};
 use euclid::{Point2D, Rect, Size2D};
@@ -1598,11 +1598,6 @@ impl Flow for InlineFlow {
             // the block-size of its containing block, which may also be an absolute flow.
             (&mut *self as &mut Flow).traverse_preorder_absolute_flows(
                 &mut AbsoluteAssignBSizesTraversal(layout_context));
-            // Store overflow for all absolute descendants.
-            (&mut *self as &mut Flow).traverse_postorder_absolute_flows(
-                &mut AbsoluteStoreOverflowTraversal {
-                    layout_context: layout_context,
-                });
         }
 
         self.base.position.size.block = match self.lines.last() {
@@ -1627,7 +1622,6 @@ impl Flow for InlineFlow {
                         relative_containing_block_size: containing_block_size,
                         relative_containing_block_mode: writing_mode,
                     };
-                    (block.as_mut_block() as &mut Flow).late_store_overflow(layout_context);
                 }
                 SpecificFragmentInfo::InlineAbsolute(ref mut info) => {
                     let block = flow_ref::deref_mut(&mut info.flow_ref);
@@ -1635,7 +1629,6 @@ impl Flow for InlineFlow {
                         relative_containing_block_size: containing_block_size,
                         relative_containing_block_mode: writing_mode,
                     };
-                    (block.as_mut_block() as &mut Flow).late_store_overflow(layout_context);
                 }
                 _ => (),
             }
diff --git a/components/layout/parallel.rs b/components/layout/parallel.rs
index 1ea9bffeb51..eddac889c50 100644
--- a/components/layout/parallel.rs
+++ b/components/layout/parallel.rs
@@ -484,9 +484,6 @@ pub fn traverse_flow_tree_preorder(
             })
         });
     }, shared_layout_context);
-
-    let layout_context = LayoutContext::new(shared_layout_context);
-    flow_ref::deref_mut(root).late_store_overflow(&layout_context);
 }
 
 pub fn build_display_list_for_subtree(
diff --git a/components/layout/sequential.rs b/components/layout/sequential.rs
index 75f121ca2cc..9202ef2ea8a 100644
--- a/components/layout/sequential.rs
+++ b/components/layout/sequential.rs
@@ -98,8 +98,6 @@ pub fn traverse_flow_tree_preorder(root: &mut FlowRef,
     let assign_block_sizes  = AssignBSizesAndStoreOverflow { layout_context: &layout_context };
 
     doit(root, assign_inline_sizes, assign_block_sizes);
-
-    root.late_store_overflow(&layout_context);
 }
 
 pub fn build_display_list_for_subtree(root: &mut FlowRef,
diff --git a/components/layout/table.rs b/components/layout/table.rs
index 62b8807de07..c3d7ec137d9 100644
--- a/components/layout/table.rs
+++ b/components/layout/table.rs
@@ -12,7 +12,7 @@ use block::{self, BlockFlow, CandidateBSizeIterator, ISizeAndMarginsComputer};
 use context::LayoutContext;
 use display_list_builder::{BlockFlowDisplayListBuilding, BorderPaintingMode};
 use euclid::{Point2D, Rect};
-use flow::{IMPACTED_BY_RIGHT_FLOATS, ImmutableFlowUtils, MutableFlowUtils, OpaqueFlow};
+use flow::{IMPACTED_BY_RIGHT_FLOATS, ImmutableFlowUtils, OpaqueFlow};
 use flow::{self, EarlyAbsolutePositionInfo, Flow, FlowClass, IMPACTED_BY_LEFT_FLOATS};
 use fragment::{Fragment, FragmentBorderBoxIterator};
 use gfx::display_list::DisplayList;
@@ -762,7 +762,7 @@ pub trait TableLikeFlow {
 
 impl TableLikeFlow for BlockFlow {
     fn assign_block_size_for_table_like_flow<'a>(&mut self,
-                                                 layout_context: &'a LayoutContext<'a>,
+                                                 _: &'a LayoutContext<'a>,
                                                  block_direction_spacing: Au) {
         debug_assert!(self.fragment.style.get_inheritedtable().border_collapse ==
                       border_collapse::T::separate || block_direction_spacing == Au(0));
@@ -842,7 +842,6 @@ impl TableLikeFlow for BlockFlow {
                     relative_containing_block_size: self.fragment.content_box().size,
                     relative_containing_block_mode: self.fragment.style().writing_mode,
                 };
-                kid.late_store_overflow(layout_context)
             }
         }
 
diff --git a/components/layout/traversal.rs b/components/layout/traversal.rs
index d833c240d63..34427b9d8d9 100644
--- a/components/layout/traversal.rs
+++ b/components/layout/traversal.rs
@@ -7,7 +7,7 @@
 use construct::FlowConstructor;
 use context::LayoutContext;
 use css::matching::{ApplicableDeclarations, ElementMatchMethods, MatchMethods, StyleSharingResult};
-use flow::{MutableFlowUtils, PostorderFlowTraversal, PreorderFlowTraversal};
+use flow::{PostorderFlowTraversal, PreorderFlowTraversal};
 use flow::{self, Flow};
 use gfx::display_list::OpaqueNode;
 use incremental::{self, BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW, RestyleDamage};
@@ -360,7 +360,6 @@ impl<'a> PostorderFlowTraversal for AssignBSizesAndStoreOverflow<'a> {
         }
 
         flow.assign_block_size(self.layout_context);
-        flow.early_store_overflow(self.layout_context);
     }
 
     #[inline]
@@ -378,6 +377,7 @@ impl<'a> PreorderFlowTraversal for ComputeAbsolutePositions<'a> {
     #[inline]
     fn process(&self, flow: &mut Flow) {
         flow.compute_absolute_position(self.layout_context);
+        flow.store_overflow(self.layout_context);
     }
 }
 
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 10980937d89..da05b5bcb77 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -15,6 +15,18 @@
     "deleted": [],
     "items": {
       "reftest": {
+        "css/abs-overflow-stackingcontext.html": [
+          {
+            "path": "css/abs-overflow-stackingcontext.html",
+            "references": [
+              [
+                "/_mozilla/css/abs-overflow-stackingcontext_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/abs-overflow-stackingcontext.html"
+          }
+        ],
         "css/abs_float_pref_width.html": [
           {
             "path": "css/abs_float_pref_width.html",
@@ -4750,6 +4762,18 @@
       }
     },
     "reftest_nodes": {
+      "css/abs-overflow-stackingcontext.html": [
+        {
+          "path": "css/abs-overflow-stackingcontext.html",
+          "references": [
+            [
+              "/_mozilla/css/abs-overflow-stackingcontext_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/abs-overflow-stackingcontext.html"
+        }
+      ],
       "css/abs_float_pref_width.html": [
         {
           "path": "css/abs_float_pref_width.html",
diff --git a/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext.html b/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext.html
new file mode 100644
index 00000000000..264df01aa64
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <link rel='match' href='abs-overflow-stackingcontext_ref.html'>
+        <style>
+            html, body {
+                margin: 0;
+                perspective: 1000px;
+            }
+
+            div {
+                position: absolute;
+                top: 25vh;
+                left: 25vw;
+                width: 50vw;
+                height: 50vh;
+                background-color: green;
+            }
+        </style>
+    </head>
+    <body>
+        <div></div>
+    </body>
+</html>
diff --git a/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext_ref.html b/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext_ref.html
new file mode 100644
index 00000000000..f779e5a4233
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/abs-overflow-stackingcontext_ref.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <style>
+            html, body {
+                margin: 0;
+            }
+
+            div {
+                position: absolute;
+                top: 25vh;
+                left: 25vw;
+                width: 50vw;
+                height: 50vh;
+                background-color: green;
+            }
+        </style>
+    </head>
+    <body>
+        <div></div>
+    </body>
+</html>