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layout: Adjust the position of block formatting contexts based on float

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placement.

Improves Reddit considerably.

Closes #3456.
This commit is contained in:
Patrick Walton 2014-09-22 17:34:29 -07:00
parent a6ff0479d9
commit 3bb4020ff8
5 changed files with 58 additions and 3 deletions
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43
components/layout/block.rs
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@ -16,7 +16,7 @@
use construct::FlowConstructor;
use context::LayoutContext;
use floats::{ClearBoth, ClearLeft, ClearRight, FloatKind, Floats, PlacementInfo};
use floats::{ClearBoth, ClearLeft, ClearRight, FloatKind, FloatLeft, Floats, PlacementInfo};
use flow::{BaseFlow, BlockFlowClass, FlowClass, Flow, ImmutableFlowUtils};
use flow::{MutableFlowUtils, PreorderFlowTraversal, PostorderFlowTraversal, mut_base};
use flow;
@ -37,7 +37,7 @@ use gfx::display_list::{FloatStackingLevel, PositionedDescendantStackingLevel};
use gfx::display_list::{RootOfStackingContextLevel};
use gfx::render_task::RenderLayer;
use servo_msg::compositor_msg::{FixedPosition, LayerId, Scrollable};
use servo_util::geometry::Au;
use servo_util::geometry::{Au, MAX_AU};
use servo_util::logical_geometry::WritingMode;
use servo_util::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize};
use std::cmp::{max, min};
@ -1463,6 +1463,39 @@ impl BlockFlow {
_ => NonformattingContext,
}
}
/// Per CSS 2.1 § 9.5, block formatting contexts' inline widths and positions are affected by
/// the presence of floats. This is the part of the assign-heights traversal that computes
/// the final inline position and width for such flows.
///
/// Note that this is part of the assign-block-sizes traversal, not the assign-inline-sizes
/// traversal as one might expect. That is because, in general, float placement cannot occur
/// until heights are assigned. To work around this unfortunate circular dependency, by the
/// time we get here we have already estimated the width of the block formatting context based
/// on the floats we could see at the time of inline-size assignment. The job of this function,
/// therefore, is not only to assign the final size but also to perform the layout again for
/// this block formatting context if our speculation was wrong.
fn assign_inline_position_for_formatting_context(&mut self) {
debug_assert!(self.formatting_context_type() != NonformattingContext);
let info = PlacementInfo {
size: LogicalSize::new(
self.fragment.style.writing_mode,
self.base.position.size.inline + self.fragment.margin.inline_start_end() +
self.fragment.border_padding.inline_start_end(),
self.fragment.border_box.size.block),
ceiling: self.base.position.start.b,
max_inline_size: MAX_AU,
kind: FloatLeft,
};
// Offset our position by whatever displacement is needed to not impact the floats.
let rect = self.base.floats.place_between_floats(&info);
self.base.position.start.i = self.base.position.start.i + rect.start.i;
// TODO(pcwalton): If the inline-size of this flow is different from the size we estimated
// earlier, lay it out again.
}
}
impl Flow for BlockFlow {
@ -1626,7 +1659,7 @@ impl Flow for BlockFlow {
}
}
// Move in from the inline-start border edge
// Move in from the inline-start border edge.
let inline_start_content_edge = self.fragment.border_box.start.i + self.fragment.border_padding.inline_start;
let padding_and_borders = self.fragment.border_padding.inline_start_end();
let content_inline_size = self.fragment.border_box.size.inline - padding_and_borders;
@ -1652,6 +1685,10 @@ impl Flow for BlockFlow {
return true
}
if self.formatting_context_type() != NonformattingContext {
self.assign_inline_position_for_formatting_context();
}
let impacted = self.base.flags.impacted_by_floats();
if impacted {
self.assign_block_size(layout_context);