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layout: Rewrite the block formatting context/float inline-size

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speculation code.

The old code tried to do the speculation as a single bottom-up pass
after intrinsic inline-size calculation, which was unable to handle
cases like this:

    <div>
        <div style="float: left">Foo</div>
    </div>
    <div>
        <div style="overflow: hidden">Bar</div>
    </div>

No single bottom-up pass could possibly handle this case, because the
inline-size of the float flowing out of the "Foo" block could never make
it down to the "Bar" block, where it is needed for speculation.

On the pages I tried, this regresses layout performance by 1%-2%.

I first noticed this breaking some pages, like the Google SERPs, several
months ago.
This commit is contained in:
Patrick Walton 2016-03-18 15:23:08 -07:00
parent 9b2ae3a62f
commit b29719e36b
15 changed files with 346 additions and 184 deletions
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18
components/layout/flex.rs
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@ -17,7 +17,6 @@ use flow::INLINE_POSITION_IS_STATIC;
use flow::IS_ABSOLUTELY_POSITIONED;
use flow::ImmutableFlowUtils;
use flow::{Flow, FlowClass, OpaqueFlow};
use flow::{HAS_LEFT_FLOATED_DESCENDANTS, HAS_RIGHT_FLOATED_DESCENDANTS};
use fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
use gfx::display_list::{StackingContext, StackingContextId};
use incremental::{REFLOW, REFLOW_OUT_OF_FLOW};
@ -26,7 +25,7 @@ use model::MaybeAuto;
use model::{IntrinsicISizes};
use std::cmp::max;
use std::sync::Arc;
use style::computed_values::{flex_direction, float};
use style::computed_values::flex_direction;
use style::logical_geometry::LogicalSize;
use style::properties::style_structs;
use style::properties::{ComputedValues, TComputedValues};
@ -324,25 +323,10 @@ impl Flow for FlexFlow {
// TODO(zentner): We need to re-order the items at some point. However, all the operations
// here ignore order, so we can afford to do it later, if necessary.
// `flex item`s (our children) cannot be floated. Furthermore, they all establish BFC's.
// Therefore, we do not have to handle any floats here.
let mut flags = self.block_flow.base.flags;
flags.remove(HAS_LEFT_FLOATED_DESCENDANTS);
flags.remove(HAS_RIGHT_FLOATED_DESCENDANTS);
match self.main_mode {
Mode::Inline => self.inline_mode_bubble_inline_sizes(),
Mode::Block => self.block_mode_bubble_inline_sizes()
}
// Although our children can't be floated, we can.
match self.block_flow.fragment.style().get_box().float {
float::T::none => {}
float::T::left => flags.insert(HAS_LEFT_FLOATED_DESCENDANTS),
float::T::right => flags.insert(HAS_RIGHT_FLOATED_DESCENDANTS),
}
self.block_flow.base.flags = flags
}
fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {