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layout: Implement proper absolute child position for flexbox (#33346)
This implements the requirements outlined in the [flexbox specification] about how to position absolute children of flex containers. We must establish a static position rectangle (to use if all insets are auto) and also align the child into that rectangle. [flebox specification]: https://drafts.csswg.org/css-flexbox/#abspos-items Signed-off-by: Martin Robinson <mrobinson@igalia.com> Co-authored-by: Oriol Brufau <obrufau@igalia.com>
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20 changed files with 678 additions and 724 deletions
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@ -4,11 +4,11 @@
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use app_units::Au;
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use serde::Serialize;
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use style::values::computed::LengthPercentage;
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use style::values::specified::align::AlignFlags;
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use super::Fragment;
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use crate::cell::ArcRefCell;
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use crate::geom::LogicalVec2;
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use crate::geom::{LogicalVec2, PhysicalRect, PhysicalVec};
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/// A reference to a Fragment which is shared between `HoistedAbsolutelyPositionedBox`
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/// and its placeholder `AbsoluteOrFixedPositionedFragment` in the original tree position.
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@ -16,53 +16,35 @@ use crate::geom::LogicalVec2;
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#[derive(Serialize)]
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pub(crate) struct HoistedSharedFragment {
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pub fragment: Option<ArcRefCell<Fragment>>,
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pub box_offsets: LogicalVec2<AbsoluteBoxOffsets>,
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/// The "static-position rect" of this absolutely positioned box. This is defined by the
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/// layout mode from which the box originates.
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///
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/// See <https://drafts.csswg.org/css-position-3/#staticpos-rect>
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pub static_position_rect: PhysicalRect<Au>,
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/// The resolved alignment values used for aligning this absolutely positioned element
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/// if the "static-position rect" ends up being the "inset-modified containing block".
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/// These values are dependent on the layout mode (currently only interesting for
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/// flexbox).
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pub resolved_alignment: LogicalVec2<AlignFlags>,
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}
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impl HoistedSharedFragment {
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pub(crate) fn new(box_offsets: LogicalVec2<AbsoluteBoxOffsets>) -> Self {
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pub(crate) fn new(
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static_position_rect: PhysicalRect<Au>,
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resolved_alignment: LogicalVec2<AlignFlags>,
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) -> Self {
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HoistedSharedFragment {
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fragment: None,
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box_offsets,
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static_position_rect,
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resolved_alignment,
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}
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}
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}
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impl HoistedSharedFragment {
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/// In some cases `inset: auto`-positioned elements do not know their precise
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/// position until after they're hoisted. This lets us adjust auto values
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/// after the fact.
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pub(crate) fn adjust_offsets(&mut self, offsets: LogicalVec2<Au>) {
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self.box_offsets.inline.adjust_offset(offsets.inline);
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self.box_offsets.block.adjust_offset(offsets.block);
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}
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}
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#[derive(Clone, Debug, Serialize)]
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pub(crate) enum AbsoluteBoxOffsets {
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StaticStart {
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start: Au,
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},
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Start {
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start: LengthPercentage,
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},
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End {
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end: LengthPercentage,
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},
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Both {
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start: LengthPercentage,
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end: LengthPercentage,
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},
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}
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impl AbsoluteBoxOffsets {
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pub(crate) fn both_specified(&self) -> bool {
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matches!(self, AbsoluteBoxOffsets::Both { .. })
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}
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pub(crate) fn adjust_offset(&mut self, new_offset: Au) {
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if let AbsoluteBoxOffsets::StaticStart { ref mut start } = *self {
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*start = new_offset
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}
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/// `inset: auto`-positioned elements do not know their precise position until after
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/// they're hoisted. This lets us adjust auto values after the fact.
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pub(crate) fn adjust_offsets(&mut self, offset: &PhysicalVec<Au>) {
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self.static_position_rect = self.static_position_rect.translate(*offset);
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}
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}
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