Auto merge of #16458 - stshine:sequential-fallback, r=pcwalton,emilio

layout: Force reflow in the sequential fallback of block format context

When reflowing a block format context during the inorder traversal,
propagate restyle damage manually to its children since they were
already reflowed. Also, test the border box to see if it can fit into
floats according to CSS 2.1 § 9.5.

Improves reddit and yahoo.

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- [X] These changes fix #__ (github issue number if applicable).

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components/layout/block.rs

@@ -43,6 +43,7 @@ use flow_list::FlowList;
 use fragment::{CoordinateSystem, Fragment, FragmentBorderBoxIterator, Overflow};
 use fragment::{IS_INLINE_FLEX_ITEM, IS_BLOCK_FLEX_ITEM};
 use gfx_traits::print_tree::PrintTree;
+use incremental::RelayoutMode;
 use layout_debug;
 use model::{AdjoiningMargins, CollapsibleMargins, IntrinsicISizes, MarginCollapseInfo, MaybeAuto};
 use model::{specified, specified_or_none};
@@ -1549,7 +1550,7 @@ impl BlockFlow {
             self.assign_inline_sizes(layout_context);
             // Re-run layout on our children.
             for child in flow::mut_base(self).children.iter_mut() {
-                sequential::traverse_flow_tree_preorder(child, layout_context);
+                sequential::traverse_flow_tree_preorder(child, layout_context, RelayoutMode::Force);
             }
             // Assign our final-final block size.
             self.assign_block_size(layout_context);

components/layout/incremental.rs

@@ -7,6 +7,13 @@ use style::computed_values::float;
 use style::selector_parser::RestyleDamage;
 use style::servo::restyle_damage::{REFLOW, RECONSTRUCT_FLOW};
 
+/// Used in a flow traversal to indicate whether this re-layout should be incremental or not.
+#[derive(Clone, Copy, PartialEq)]
+pub enum RelayoutMode {
+    Incremental,
+    Force
+}
+
 bitflags! {
     pub flags SpecialRestyleDamage: u8 {
         #[doc = "If this flag is set, we need to reflow the entire document. This is more or less a \

components/layout/sequential.rs

@@ -14,8 +14,9 @@ use flow::{PostorderFlowTraversal, PreorderFlowTraversal};
 use flow::IS_ABSOLUTELY_POSITIONED;
 use fragment::FragmentBorderBoxIterator;
 use generated_content::ResolveGeneratedContent;
+use incremental::RelayoutMode;
 use servo_config::opts;
-use style::servo::restyle_damage::{REFLOW, STORE_OVERFLOW};
+use style::servo::restyle_damage::{REFLOW, REFLOW_OUT_OF_FLOW, STORE_OVERFLOW};
 use traversal::{AssignBSizes, AssignISizes, BubbleISizes, BuildDisplayList};
 
 pub use style::sequential::traverse_dom;
@@ -38,16 +39,24 @@ pub fn resolve_generated_content(root: &mut Flow, layout_context: &LayoutContext
 }
 
 pub fn traverse_flow_tree_preorder(root: &mut Flow,
-                                   layout_context: &LayoutContext) {
+                                   layout_context: &LayoutContext,
+                                   relayout_mode: RelayoutMode) {
     fn doit(flow: &mut Flow,
             assign_inline_sizes: AssignISizes,
-            assign_block_sizes: AssignBSizes) {
+            assign_block_sizes: AssignBSizes,
+            relayout_mode: RelayoutMode) {
+        // Force reflow children during this traversal. This is needed when we failed
+        // the float speculation of a block formatting context and need to fix it.
+        if relayout_mode == RelayoutMode::Force {
+            flow::mut_base(flow).restyle_damage.insert(REFLOW_OUT_OF_FLOW | REFLOW);
+        }
+
         if assign_inline_sizes.should_process(flow) {
             assign_inline_sizes.process(flow);
         }
 
         for kid in flow::child_iter_mut(flow) {
-            doit(kid, assign_inline_sizes, assign_block_sizes);
+            doit(kid, assign_inline_sizes, assign_block_sizes, relayout_mode);
         }
 
         if assign_block_sizes.should_process(flow) {
@@ -66,7 +75,7 @@ pub fn traverse_flow_tree_preorder(root: &mut Flow,
     let assign_inline_sizes = AssignISizes { layout_context: &layout_context };
     let assign_block_sizes  = AssignBSizes { layout_context: &layout_context };
 
-    doit(root, assign_inline_sizes, assign_block_sizes);
+    doit(root, assign_inline_sizes, assign_block_sizes, relayout_mode);
 }
 
 pub fn build_display_list_for_subtree<'a>(flow_root: &mut Flow,

components/layout_thread/lib.rs

@@ -60,7 +60,7 @@ use layout::context::heap_size_of_persistent_local_context;
 use layout::display_list_builder::ToGfxColor;
 use layout::flow::{self, Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
 use layout::flow_ref::FlowRef;
-use layout::incremental::{LayoutDamageComputation, REFLOW_ENTIRE_DOCUMENT};
+use layout::incremental::{LayoutDamageComputation, REFLOW_ENTIRE_DOCUMENT, RelayoutMode};
 use layout::layout_debug;
 use layout::opaque_node::OpaqueNodeMethods;
 use layout::parallel;
@@ -811,7 +811,7 @@ impl LayoutThread {
     fn solve_constraints(layout_root: &mut Flow,
                          layout_context: &LayoutContext) {
         let _scope = layout_debug_scope!("solve_constraints");
-        sequential::traverse_flow_tree_preorder(layout_root, layout_context);
+        sequential::traverse_flow_tree_preorder(layout_root, layout_context, RelayoutMode::Incremental);
     }
 
     /// Performs layout constraint solving in parallel.

tests/wpt/metadata-css/css21_dev/html4/floats-038.htm.ini

@@ -1,3 +0,0 @@
-[floats-038.htm]
-  type: reftest
-  expected: FAIL

tests/wpt/metadata-css/css21_dev/html4/floats-wrap-bfc-002-left-table.htm.ini

@@ -1,3 +0,0 @@
-[floats-wrap-bfc-002-left-table.htm]
-  type: reftest
-  expected: FAIL