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Do not hoist floated fragments

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Instead of hoisting floated fragments to be siblings of the fragment
created by their containing block formatting context, keep them in
"normal" fragment tree position and adjust their positioning to be
relative to the containing block. This means that float fragments follow
the existing invariants of the fragment tree and properly handle hit
testing, painting order, and relative positioning.

The tradeoff here is more complexity tracking the containing block
offsets from the block formatting context (including handling collapsed
margins), but less complexity dealing with hoisting / shared ownership
in addition to the correctness benefits.

Some tests are failing now because this change revealed some additional
shortcomings with clearing block formatting context content size past
the end of their contained floats. This will be fixed in a followup
change.

Co-authored-by: Oriol Brufau <obrufau@igalia.com>
This commit is contained in:
Martin Robinson 2023-05-25 13:12:22 +02:00 • committed by Oriol Brufau
parent cdec48328e
commit 25f6cc04a2
22 changed files with 250 additions and 296 deletions
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116
components/layout_2020/flow/mod.rs
View file

@ -4,9 +4,11 @@
//! Flow layout, also known as block-and-inline layout.
use std::ops::DerefMut;
use crate::cell::ArcRefCell;
use crate::context::LayoutContext;
use crate::flow::float::{ClearSide, FloatBox, SequentialLayoutState};
use crate::flow::float::{ClearSide, ContainingBlockPositionInfo, FloatBox, SequentialLayoutState};
use crate::flow::inline::InlineFormattingContext;
use crate::formatting_contexts::{
IndependentFormattingContext, IndependentLayout, NonReplacedFormattingContext,
@ -82,7 +84,7 @@ impl BlockFormattingContext {
None
};
let mut flow_layout = self.contents.layout(
let flow_layout = self.contents.layout(
layout_context,
positioning_context,
containing_block,
@ -96,11 +98,6 @@ impl BlockFormattingContext {
.collapsed_through
);
// FIXME(pcwalton): Relative positioning of ancestors should affect descendant floats.
if let Some(ref sequential_layout_state) = sequential_layout_state {
sequential_layout_state.add_float_fragments_to_list(&mut flow_layout.fragments);
}
IndependentLayout {
fragments: flow_layout.fragments,
content_block_size: flow_layout.content_block_size +
@ -267,7 +264,10 @@ fn layout_block_level_children_sequentially(
tree_rank,
Some(&mut *sequential_layout_state),
);
placement_state.place_fragment(&mut fragment);
placement_state
.adjust_positions_of_float_children(&mut fragment, sequential_layout_state);
fragment
})
.collect()
@ -364,15 +364,12 @@ impl BlockLevelBox {
positioning_context.push(hoisted_box);
Fragment::AbsoluteOrFixedPositioned(hoisted_fragment)
},
BlockLevelBox::OutOfFlowFloatBox(box_) => {
box_.layout(
layout_context,
positioning_context,
containing_block,
sequential_layout_state,
);
Fragment::Float
},
BlockLevelBox::OutOfFlowFloatBox(box_) => box_.layout(
layout_context,
positioning_context,
containing_block,
sequential_layout_state,
),
}
}
@ -489,9 +486,9 @@ fn layout_in_flow_non_replaced_block_level(
min_box_size.block == Length::zero();
let mut clearance = Length::zero();
let old_inline_walls;
let parent_containing_block_position_info;
match sequential_layout_state {
None => old_inline_walls = None,
None => parent_containing_block_position_info = None,
Some(ref mut sequential_layout_state) => {
sequential_layout_state.adjoin_assign(&CollapsedMargin::new(margin.block_start));
if !start_margin_can_collapse_with_children {
@ -508,12 +505,26 @@ fn layout_in_flow_non_replaced_block_level(
pbm.padding.block_start + pbm.border.block_start + clearance,
);
// Store our old inline walls so we can reset them later.
old_inline_walls = Some(sequential_layout_state.floats.walls);
sequential_layout_state.floats.walls.left +=
pbm.padding.inline_start + pbm.border.inline_start + margin.inline_start;
sequential_layout_state.floats.walls.right =
sequential_layout_state.floats.walls.left + inline_size;
// We are about to lay out children. Update the offset between the block formatting
// context and the containing block that we create for them. This offset is used to
// ajust BFC relative coordinates to coordinates that are relative to our content box.
// Our content box establishes the containing block for non-abspos children, including
// floats.
let inline_start = sequential_layout_state
.floats
.containing_block_info
.inline_start +
pbm.padding.inline_start +
pbm.border.inline_start +
margin.inline_start;
let new_cb_offsets = ContainingBlockPositionInfo {
block_start: sequential_layout_state.bfc_relative_block_position,
block_start_margins_not_collapsed: sequential_layout_state.current_margin,
inline_start,
inline_end: inline_start + inline_size,
};
parent_containing_block_position_info =
Some(sequential_layout_state.update_all_containing_block_offsets(new_cb_offsets));
},
};
@ -579,8 +590,10 @@ fn layout_in_flow_non_replaced_block_level(
});
if let Some(ref mut sequential_layout_state) = sequential_layout_state {
// Now that we're done laying out our children, we can restore the old inline walls.
sequential_layout_state.floats.walls = old_inline_walls.unwrap();
// Now that we're done laying out our children, we can restore the
// parent's containing block position information.
sequential_layout_state
.update_all_containing_block_offsets(parent_containing_block_position_info.unwrap());
// Account for padding and border. We also might have to readjust the
// `bfc_relative_block_position` if it was different from the content size (i.e. was
@ -749,7 +762,7 @@ impl PlacementState {
};
fragment.borrow_mut().adjust_offsets(offset);
},
Fragment::Anonymous(_) | Fragment::Float => {},
Fragment::Anonymous(_) | Fragment::Float(_) => {},
_ => unreachable!(),
}
}
@ -761,4 +774,53 @@ impl PlacementState {
end: self.current_margin,
}
}
/// When Float fragments are created in block flows, they are positioned
/// relative to the float containing independent block formatting context.
/// Once we place a float's containing block, this function can be used to
/// fix up the float position to be relative to the containing block.
fn adjust_positions_of_float_children(
&self,
fragment: &mut Fragment,
sequential_layout_state: &mut SequentialLayoutState,
) {
let fragment = match fragment {
Fragment::Box(ref mut fragment) => fragment,
_ => return,
};
// TODO(mrobinson): Will these margins be accurate if this fragment
// collapses through. Can a fragment collapse through when it has a
// non-zero sized float inside? The float won't be positioned correctly
// anyway (see the comment in `floats.rs` about margin collapse), but
// this might make the result even worse.
let collapsed_margins = self.collapsible_margins_in_children().start.adjoin(
&sequential_layout_state
.floats
.containing_block_info
.block_start_margins_not_collapsed,
);
let parent_fragment_offset_in_cb = &fragment.content_rect.start_corner;
let parent_fragment_offset_in_formatting_context = Vec2 {
inline: sequential_layout_state
.floats
.containing_block_info
.inline_start +
parent_fragment_offset_in_cb.inline,
block: sequential_layout_state
.floats
.containing_block_info
.block_start +
collapsed_margins.solve() +
parent_fragment_offset_in_cb.block,
};
for child_fragment in fragment.children.iter_mut() {
if let Fragment::Float(box_fragment) = child_fragment.borrow_mut().deref_mut() {
box_fragment.content_rect.start_corner = &box_fragment.content_rect.start_corner -
&parent_fragment_offset_in_formatting_context;
}
}
}
}