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layout: Disallow margins from collapsing through blocks with clearance

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per CSS 2.1 § 8.3.1.

Fixes the test failure in #10458.
This commit is contained in:
Patrick Walton 2016-04-12 14:09:29 -07:00
parent e32455f7b8
commit a3fd226341
37 changed files with 223 additions and 94 deletions
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28
components/layout/model.rs
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@ -18,7 +18,7 @@ use style::values::computed::{BorderRadiusSize, LengthOrPercentageOrAuto};
use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrNone};
/// A collapsible margin. See CSS 2.1 § 8.3.1.
#[derive(Copy, Clone)]
#[derive(Copy, Clone, Debug)]
pub struct AdjoiningMargins {
/// The value of the greatest positive margin.
pub most_positive: Au,
@ -61,7 +61,7 @@ impl AdjoiningMargins {
}
/// Represents the block-start and block-end margins of a flow with collapsible margins. See CSS 2.1 § 8.3.1.
#[derive(Copy, Clone)]
#[derive(Copy, Clone, Debug)]
pub enum CollapsibleMargins {
/// Margins may not collapse with this flow.
None(Au, Au),
@ -169,12 +169,14 @@ impl MarginCollapseInfo {
FinalMarginState::MarginsCollapseThrough => {
let advance = self.block_start_margin.collapse();
self.margin_in.union(AdjoiningMargins::from_margin(block_end_margin));
(CollapsibleMargins::Collapse(self.block_start_margin, self.margin_in), advance)
(CollapsibleMargins::Collapse(self.block_start_margin, self.margin_in),
advance)
}
FinalMarginState::BottomMarginCollapses => {
let advance = self.margin_in.collapse();
self.margin_in.union(AdjoiningMargins::from_margin(block_end_margin));
(CollapsibleMargins::Collapse(self.block_start_margin, self.margin_in), advance)
(CollapsibleMargins::Collapse(self.block_start_margin, self.margin_in),
advance)
}
}
} else {
@ -206,8 +208,14 @@ impl MarginCollapseInfo {
/// Adds the child's potentially collapsible block-start margin to the current margin state and
/// advances the Y offset by the appropriate amount to handle that margin. Returns the amount
/// that should be added to the Y offset during block layout.
pub fn advance_block_start_margin(&mut self, child_collapsible_margins: &CollapsibleMargins)
pub fn advance_block_start_margin(&mut self,
child_collapsible_margins: &CollapsibleMargins,
can_collapse_block_start_margin: bool)
-> Au {
if !can_collapse_block_start_margin {
self.state = MarginCollapseState::AccumulatingMarginIn
}
match (self.state, *child_collapsible_margins) {
(MarginCollapseState::AccumulatingCollapsibleTopMargin,
CollapsibleMargins::None(block_start, _)) => {
@ -226,14 +234,16 @@ impl MarginCollapseInfo {
self.margin_in = AdjoiningMargins::new();
previous_margin_value + block_start
}
(MarginCollapseState::AccumulatingMarginIn, CollapsibleMargins::Collapse(block_start, _)) => {
(MarginCollapseState::AccumulatingMarginIn,
CollapsibleMargins::Collapse(block_start, _)) => {
self.margin_in.union(block_start);
let margin_value = self.margin_in.collapse();
self.margin_in = AdjoiningMargins::new();
margin_value
}
(_, CollapsibleMargins::CollapseThrough(_)) => {
// For now, we ignore this; this will be handled by `advance_block-end_margin` below.
// For now, we ignore this; this will be handled by `advance_block_end_margin`
// below.
Au(0)
}
}
@ -274,9 +284,11 @@ impl MarginCollapseInfo {
}
}
#[derive(Copy, Clone)]
#[derive(Copy, Clone, Debug)]
pub enum MarginCollapseState {
/// We are accumulating margin on the logical top of this flow.
AccumulatingCollapsibleTopMargin,
/// We are accumulating margin between two blocks.
AccumulatingMarginIn,
}