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layout: Rewrite clipping to be a two-phase process that takes physical

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border box positions and transforms into account.

Clipping region computation now follows a simple process: (1) in the
parent's coordinate system, parents store appropriate clipping regions
into children; (2) each child moves its clipping region to its own
coordinate system if necessary.

Because clipping region computation is now based on stacking-relative
border box positions and the `transform_rect` method, it can handle
`position: relative` offsets and more types of transforms, such as
scaling.

Improves etsy.com.

Closes #13753.
This commit is contained in:
Patrick Walton 2016-10-13 14:48:30 -07:00 • committed by Michael Howell
parent 759185abe0
commit 7df456e8ac
9 changed files with 251 additions and 162 deletions
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88
components/layout/block.rs
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@ -47,8 +47,8 @@ use gfx::display_list::{ClippingRegion, StackingContext};
use gfx_traits::LayerId;
use gfx_traits::print_tree::PrintTree;
use layout_debug;
use model::{self, IntrinsicISizes, MarginCollapseInfo};
use model::{CollapsibleMargins, MaybeAuto, specified, specified_or_none};
use model::{CollapsibleMargins, IntrinsicISizes, MarginCollapseInfo, MaybeAuto};
use model::{specified, specified_or_none};
use rustc_serialize::{Encodable, Encoder};
use script_layout_interface::restyle_damage::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW};
use script_layout_interface::restyle_damage::REPOSITION;
@ -57,7 +57,7 @@ use std::cmp::{max, min};
use std::fmt;
use std::sync::Arc;
use style::computed_values::{border_collapse, box_sizing, display, float, overflow_x, overflow_y};
use style::computed_values::{position, text_align, transform, transform_style};
use style::computed_values::{position, text_align, transform_style};
use style::context::{SharedStyleContext, StyleContext};
use style::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize, WritingMode};
use style::properties::ServoComputedValues;
@ -2070,12 +2070,9 @@ impl Flow for BlockFlow {
self.base.position.size.to_physical(self.base.writing_mode);
// Compute the origin and clipping rectangle for children.
//
// `clip` is in the child coordinate system.
let mut clip;
let origin_for_children;
let relative_offset = relative_offset.to_physical(self.base.writing_mode);
let is_stacking_context = self.fragment.establishes_stacking_context();
if is_stacking_context {
let origin_for_children = if is_stacking_context {
// We establish a stacking context, so the position of our children is vertically
// correct, but has to be adjusted to accommodate horizontal margins. (Note the
// calculation involving `position` below and recall that inline-direction flow
@ -2083,13 +2080,10 @@ impl Flow for BlockFlow {
//
// FIXME(pcwalton): Is this vertical-writing-direction-safe?
let margin = self.fragment.margin.to_physical(self.base.writing_mode);
origin_for_children = Point2D::new(-margin.left, Au(0));
clip = self.base.clip.translate(&-self.base.stacking_relative_position);
Point2D::new(-margin.left, Au(0))
} else {
let relative_offset = relative_offset.to_physical(self.base.writing_mode);
origin_for_children = self.base.stacking_relative_position + relative_offset;
clip = self.base.clip.clone();
}
self.base.stacking_relative_position + relative_offset
};
let stacking_relative_position_of_display_port_for_children =
if is_stacking_context || self.is_root() {
@ -2120,9 +2114,17 @@ impl Flow for BlockFlow {
.early_absolute_position_info
.relative_containing_block_mode,
CoordinateSystem::Own);
self.fragment.adjust_clipping_region_for_children(
&mut clip,
&stacking_relative_border_box);
// Our parent set our `clip` field to the clipping region in its coordinate system. Change
// it to our coordinate system.
self.switch_coordinate_system_if_necessary();
self.fragment.adjust_clip_for_style(&mut self.base.clip, &stacking_relative_border_box);
// Compute the clipping region for children, taking our `overflow` properties and so forth
// into account.
let mut clip_for_children = self.base.clip.clone();
self.fragment.adjust_clipping_region_for_children(&mut clip_for_children,
&stacking_relative_border_box);
// Process children.
for kid in self.base.child_iter_mut() {
@ -2166,50 +2168,18 @@ impl Flow for BlockFlow {
flow::mut_base(kid).late_absolute_position_info =
late_absolute_position_info_for_children;
let clip = if kid.is_block_like() {
let mut clip = clip.clone();
let kid = kid.as_block();
// TODO(notriddle): To properly support transformations, we either need
// non-rectangular clipping regions in display lists, or clipping
// regions in terms of the parent coordinate system instead of the
// child coordinate system.
//
// This is a workaround for a common idiom of transform: translate().
if let Some(ref operations) = kid.fragment.style().get_effects().transform.0 {
for operation in operations {
match *operation {
transform::ComputedOperation::Translate(tx, ty, _) => {
// N.B. When the clipping value comes from us, it
// shouldn't be transformed.
let tx = if let overflow_x::T::hidden = kid.fragment.style().get_box()
.overflow_x {
Au(0)
} else {
model::specified(tx, kid.base.block_container_inline_size)
};
let ty = if let overflow_x::T::hidden = kid.fragment.style().get_box()
.overflow_y.0 {
Au(0)
} else {
model::specified(
ty,
kid.base.block_container_explicit_block_size.unwrap_or(Au(0))
)
};
let off = Point2D::new(tx, ty);
clip = clip.translate(&-off);
}
_ => {}
};
}
}
clip
} else {
clip.clone()
};
flow::mut_base(kid).clip = clip;
flow::mut_base(kid).stacking_relative_position_of_display_port =
stacking_relative_position_of_display_port_for_children;
// This clipping region is in our coordinate system. The child will fix it up to be in
// its own coordinate system by itself if necessary.
//
// Rationale: If the child is absolutely positioned, it hasn't been positioned at this
// point (as absolutely-positioned flows position themselves in
// `compute_absolute_position()`). Therefore, we don't always know what the child's
// coordinate system is here. So we store the clipping region in our coordinate system
// for now; the child will move it later if needed.
flow::mut_base(kid).clip = clip_for_children.clone()
}
self.base.restyle_damage.remove(REPOSITION)