layout_2020: Do linebreak for atomic inline-level elements
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Properly position floats when subsequent boxes collapse margins with containing block (2)
PR #29939 tried to address this but missed various cases.
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Clearance was implemented as a Length, where zero meant no clearance.
However, having a clearance of 0px should be different than having
no clearance, since the former can still prevent margin collapse.
This patch keeps the existing behavior, so it won't be possible to get
a clearance of Some(Length::zero()), but it prepares the terrain for
a follow-up to fix calculate_clearance to return the proper thing.
Margins should be able to collapse through floats when collapsing with
parent blocks (the containing block). To properly place floats in this
situation, we need to look at these subsequent floats to find out how
much of the margin will collapse with the parent.
This initial implementation is very basic and the second step would be
to cache this in order to avoid having to constantly recalculate it.
Fixes#29915.
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
Increase BFC root height to contain floats
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Previously, final float positions were calculated when their parents
were positioned. This prevented proper positioning of absolute children
of floats with static insets, because they accumulate offsets as they
are hoisted up the tree.
This change moves the final float positioning to
`PlacementState::place_fragment` for the float itself so that it happens
before any insets are updated for hoisted descendants. In addition to
simplifying the code, this makes it a bit more efficient. Finally,
floats are taken into account when updating static insets of hoisted
boxes.
Fixes#29826.
In #29897 I did the simple naive thing, but it wasn't entirely correct.
This patch tries to address the problems. In particular:
- Clearance should prevent margins from collapsing through if it
happens between them, as opposed to on the element that owns them.
- The margins of an element with clearance can still collapse through,
and collapse with other siblings as normal, but the resulting
margin can't collapse with the bottom margin of the parent.
Simplify layout of absolutes with static insets
Absolutes with static insets need to be laid out at their ancestor containing blocks, but their position is dependent on their parent's layout. The static layout position is passed up the tree during hoisting and ancestors each add their own offset to the position until it is relative to the containing block that contains the absolute.
This is currently done with a closure and a fairly tricky "tree rank" numbering system that needs to be threaded through the entire layout. This change replaces that system.
Every time a child is laid out we create a positioning context to hold any absolute children (this can be optimized away at a later time). At each of these moments, we call a method to aggregate offsets to the static insets of hoisted absolutes. This makes the logic easier to follow and will also allow implementing this behavior for inline-blocks, which was impossible with the old system.
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Prevent margins from collapsing through when separated by clearance
This fixes#29884 and improves #29896.
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Layout 2020: Correct rendering of floated root
Fix two issues around floating a root element:
1. In the StackingContext code handle the case where a root element is a Float fragment and not a Box fragment. This fixes a debug assertion failure in the css/CSS2/float/float-root.html test.
2. When initializing the SequentialLayoutState, use the containing block width as the maximum inline float placement position instead of infinity. This fixes the rendering of css/CSS2/float/float-root.html.
Note that css/CSS2/float/float-root.html was passing before, because both the test and reference were subject to the same bug. This fixes a couple other tests as well.
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Fix two issues around floating a root element:
1. In the StackingContext code handle the case where a root element is a
Float fragment and not a Box fragment. This fixes a debug assertion
failure in the css/CSS2/float/float-root.html test.
2. When initializing the SequentialLayoutState, use the containing block
width as the maximum inline float placement position instead of
infinity. This fixes the rendering of css/CSS2/float/float-root.html.
Note that css/CSS2/float/float-root.html was passing before, because
both the test and reference were subject to the same bug. This fixes a
couple other tests as well.
Absolutes with static insets need to be laid out at their ancestor
containing blocks, but their position is dependent on their parent's
layout. The static layout position is passed up the tree during hoisting
and ancestors each add their own offset to the position until it is
relative to the containing block that contains the absolute.
This is currently done with a closure and a fairly tricky "tree rank"
numbering system that needs to be threaded through the entire layout.
This change replaces that system.
Every time a child is laid out we create a positioning context to hold
any absolute children (this can be optimized away at a later time). At
each of these moments, we call a method to aggregate offsets to the
static insets of hoisted absolutes. This makes the logic easier to
follow and will also allow implementing this behavior for inline-blocks,
which was impossible with the old system.
Typically, block-level contents are stacked vertically, so this was just
taking the maximum size among all contents. However, floats can be
stacked horizontally, so we need to sum their sizes.
Implement BlockLevelBox::inline_content_sizes for floats
This improves #29874, but `BlockContainer::inline_content_sizes` will still need more changes in order to correctly handle sequences of floats.
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Don't pass float stacking containers up to parent stacking contexts
Don't pass up float stacking containers to parent stacking contexts
Instead of passing up stacking containers created by floated content,
keep them in their original parent stacking containers. This is in in
line with specification text for stacking containers:
> To paint a stacking container, given a box root and a canvas canvas:
>
> 1. Paint a stacking context given root and canvas, treating root as
> if it created a new stacking context, but omitting any positioned
> descendants or descendants that actually create a stacking context
> (letting the parent stacking context paint them, instead).
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Instead of passing up stacking containers created by floated content,
keep them in their original parent stacking containers. This is in in
line with specification text for stacking containers:
> To paint a stacking container, given a box root and a canvas canvas:
>
> 1. Paint a stacking context given root and canvas, treating root as
> if it created a new stacking context, but omitting any positioned
> descendants or descendants that actually create a stacking context
> (letting the parent stacking context paint them, instead).
Fix some rustdoc comments which won't process properly unless they start
with three '/' characters. In addition, improve the name of a function
and add some missing documentation.
Layout 2020: Properly handle negative margins in floats
If a float has negative block margins, it should be pushed upward, but shouldn't affect the positioning of any floats that came before it. It should lower the ceiling though when it still has some non-negative block contribution. In order to implement this behavior, we should only place the float considering its non-negative block length contribution. If the float is pushed up completely past it's "natural" position, it should be placed like a float with zero block size.
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If a float has negative block margins, it should be pushed upward, but
shouldn't affect the positioning of any floats that came before it. It
should lower the ceiling though when it still has some non-negative
block contribution. In order to implement this behavior, we should only
place the float considering its non-negative block length contribution. If
the float is pushed up completely past it's "natural" position, it
should be placed like a float with zero block size.
Fix infinite loop in flexbox algorithm
Only apply step 5c of "resolve flexible lengths" if sum of scaled flexible shrink factors > 0
Probably fixes#29852 (but speculative as I can't get mach to run).
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According to https://drafts.csswg.org/css2/#collapsing-margins, bottom
margins should only collapse with the last child if `height` is `auto`.
Also, the note mentions `min-height: 0`, but the normative text doesn't
have such requirement, so I'm dropping it, matching WebKit.
The previous logic is moved into the case of collapsing the top and
bottom margins of the same element, since this can happen either with
`height: auto` or `height: 0`, and requires `min-height: 0`.
Layout 2020: Move all Fragment code to the `fragment_tree` directory
This is a simple code organization change with no behavior change with the idea of making Layout 2020 easier to understand by new folks to the project. The idea is that we will have a cleaner separation between the different parts of layout ie one directory for the fragment tree and one (currently multiple) directory for the box tree.
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This is a simple code organization change with no behavior change with
the idea of making Layout 2020 easier to understand by new folks to the
project. The idea is that we will have a cleaner separation between the
different parts of layout ie one directory for the fragment tree and one
(currently multiple) directory for the box tree.
Lay out floats and handle clearance in layout 2020, but don't flow text around them yet
This is a crude rebase of #27539
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layout_2020: Implement automatic minimum size of flex items
Implement the algorithm described in
https://drafts.csswg.org/css-flexbox/#min-size-auto.
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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 puts floats behind the `layout.floats.enabled` pref, because of the
following issues and unimplemented features:
* Inline formatting contexts don't take floats into account, so text doesn't
flow around the floats yet.
* Non-floated block formatting contexts don't take floats into account, so BFCs
can overlap floats.
* Block formatting contexts that contain floats don't expand vertically to
contain all the floats. That is, floats can stick out the bottom of BFCs,
contra spec.
Clear PositioningContext for speculative layouts
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Developed in collaboration with @mrobinson
`try_layout` is used for laying out absolutely positioned descendants multiple times when min/max-{width, height} properties are set. When the same PositioningContext instance is used between successive attempts without clearing the accumulated descendants, we will generate multiple fragments which reference the same box, which then will lead to a double borrow error when layout is performed in parallel.
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layout_2020: Only count for content size for height of non-replaced inline elements
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Accorinding to https://drafts.csswg.org/css2/#inline-non-replaced, The vertical padding, border and margin of an inline, non-replaced box start at the top and bottom of the content area, and has nothing to do with the line-height. But only the line-height is used when calculating the height of the line box.
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`try_layout` is used for laying out absolutely positioned
descendants multiple times when min/max-{width, height}
properties are set. When the same PositioningContext instance
is used between successive attempts without clearing the accumulated
descendants, we will generate multiple fragments which reference
the same box, which then will lead to a double borrow error
when layout is performed in parallel.
Signed-off-by: Mukilan Thiyagarajan <me@mukilan.in>
layout_2020: Specify the used cross size when replaced item is stretched
According to spec, if the flex item has [align-self: stretch](https://drafts.csswg.org/css-flexbox/#propdef-align-self), redo layout for its contents, treating this used size as its definite cross size so that percentage-sized children can be resolved.
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inline elements
Accorinding to https://drafts.csswg.org/css2/#inline-non-replaced, The
vertical padding, border and margin of an inline, non-replaced box
start at the top and bottom of the content area, and has nothing to do
with the line-height. But only the line-height is used when
calculating the height of the line box.
If the flex item has align-self: stretch, redo layout for its
contents, reating this used size as its definite cross size so that
percentage-sized children can be resolved.
