- Add explanatory comments.
- Rename some methods.
- Store the ceiling instead of relying on the first band, this allows
calling place() when current_bands is empty.
- Make current_bands_height() work when current_bands is empty.
- Add add_one_band() helper method.
- Make place() return a Rect. Follow-up patches will need to know the
size of the area shrunk by floats.
This will be useful for #30057 and #30050.
Co-authored-by: Martin Robinson <mrobinson@igalia.com>
No difference in behavior, just these changes:
- PlacementAmongFloats::new() initializes the top of the 1st band to the
ceiling, so that other methods can just refer to the former without
having to floor by the later.
- In fact, the 'ceiling' field becomes unnecessary, and is removed.
- top_of_placement_for_current_bands() is renamed to current_ceiling().
- try_place_once() is reorganized to reduce indentation.
- The condition 'len() > 0' becomes '!is_empty()'.
- The 1st band is now popped in place() instead of try_place_once(),
then it's easier to see why the loop will end.
Consumers of PlacementAmongFloats weren't handling margins properly.
They were assuming that they would either get a positive adjustment,
or zero for no-op.
However, just like the regular clearance triggered by 'clear', the
clearance added onto blocks that establish an independent FC can be
zero or negative, and the effect is different than having no clearance.
Since #29950, unit tests were only running with the legacy layout, and
there was no way to run them for layout 2020.
This patch makes './mach test-unit' run unit tests for both.
Also doing some changes so that the layout 2020 floats.rs tests compile.
* Place replaced and non-auto inline size independent FCs next to floats
The CSS2 specification says that replaced content and independent
formatting contexts should be placed next to floats. This change adds
support for that, but punts on support for independent formatting
contexts that have an auto inline size. With an auto inline size, we
which requires a much more complex layout algorithm.
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
* Fix issue with where last band was taken into account for inline size
* adjustment_from_floats should prevent margin collapse
* Properly handle elements with 0 height
---------
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
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>
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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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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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes
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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.
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.
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.
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.
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.
context, to place floats in layout 2020.
The containing block for a float is not necessarily the same as the block
formatting context the float is in per CSS 2.1 [1]:
"For other elements, if the element’s position is relative or static, the
containing block is formed by the content edge of the nearest block container
ancestor box."
This shows up in the simplest case:
<html>
<body>
<div style="float: left">Hello</div>
</body>
</html>
In this case, the `<html>` element is the block formatting context with inline
size equal to the width of the window, but the `<body>` element with nonzero
inline margins is the containing block for the float. The float placement must
respect the content box of the `<body>` element (i.e. floats must not overlap
the `<body>` element's margins), not that of the `<html>` element.
Because a single block formatting context may contain floats with different
containing blocks, the left and right "walls" of that containing block become
properties of individual floats at the time of placement, not properties of the
float context itself.
Additionally, this commit generalizes the float placement logic a bit to allow
the placement of arbitrary objects, not just floats. This is intended to
support inline layout and block formatting context placement.
This commit updates the `FloatContext` and associated tests only and doesn't
actually wire the context up to the rest of layout, so floats in pages still
aren't actually laid out.
[1]: https://drafts.csswg.org/css2/#containing-block-details
2020, not yet wired to the rest of layout.
This commit implements an object that handles the 10 rules in CSS 2.1:
https://www.w3.org/TR/CSS2/visuren.html#float-position
The implementation strategy is that of a persistent balanced binary search tree
of float bands. Binary search trees are commonly used for implementing float
positioning; e.g. by WebKit. Persistence enables each object that interacts
with floats to efficiently contain a snapshot of the float list at the time
that object was laid out. That way, incremental layout can invalidate and start
reflow at any point in a containing block.
This commit features extensive use of
[QuickCheck](https://github.com/BurntSushi/quickcheck) to ensure that the rules
of the CSS specification are followed.
Because this is not yet connected to layout, floats will not actually be laid
out in Web pages yet.
Note that unit tests as set up in Servo currently require types that they
access to be public. Therefore, some internal layout 2020 types that were
previously private have been made public. This is somewhat unfortunate.
Part of #25167.
Percentage `width` are treated as `auto` for the purpose of
min/max-content computation, so they also need to be considered
when testing “wether width is auto”
… and has a private enum for its contents.
Privacy forces the rest of the code to go through methods
rather than matching on the enum,
reducing accidental layout-mode-specific behavior.
