Add optional tracing that prints a tree visualization of formatting
context `run()` invocations. This is useful for debugging layout issues
where you need to understand the nesting and order of layout passes,
or why a box receives unexpected available space.
Example output:
```
├─ BFC <Viewport<#document>> run(definite(800) x definite(600))
│ ├─ BFC <BlockContainer<HTML>> run(definite(800) x indefinite)
│ │ ├─ IFC <BlockContainer(anonymous)> run(definite(800) x indefinite)
│ │ ├─ GFC <Box<DIV.grid>> run(definite(800) x indefinite)
│ │ │ ├─ BFC <BlockContainer<DIV.item>> run(definite(400) x indefinite)
```
For grid items with auto preferred size, stretch/normal alignment, and
no auto margins, the final size is simply the containing block size
minus margin box sizes. We can compute this directly without calling
`calculate_fit_content_width/height`, which triggers expensive intrinsic
sizing layout passes.
Previously, GridFormattingContext handled its own min-height constraints
internally, which caused infinite recursion when min-height was an
intrinsic sizing keyword (e.g., min-height: max-content).
This change moves the responsibility to the parent formatting context
(BFC). When any box establishing an independent formatting context has
auto height but non-auto min-height:
1. BFC measures content height using a throwaway LayoutState
2. If content height < min-height, BFC passes min-height as definite
available height to the child formatting context
3. Child FC runs once with correct constraints, unaware of min-height
Fixes https://github.com/LadybirdBrowser/ladybird/issues/4261 which
is corresponding to stack overflow on https://claude.ai/
When an item is placed with an unpositioned start and a positioned end
(e.g., `grid-row: auto / 1`), allow the start position to be negative.
This correctly creates implicit tracks before the explicit grid.
When distributing item contributions among flexible tracks with
intrinsic min sizing functions, we were skipping distribution entirely
when total_flex == 0. However, tracks like `0fr` (equivalent to
minmax(auto, 0fr)) should still receive the item's contribution
distributed equally among them.
Now we count intrinsic flexible tracks separately and distribute
equally when all flex factors are zero.
This commit includes two interdependent changes that must be applied
together:
- Treat `fit-content()` tracks as having an intrinsic min sizing
function when the limit resolves to zero.
- When clamping growth limit to fit-content limit, use `max(base_size,
fit_content_limit)` instead of just `fit_content_limit` to preserve
intrinsic sizing contributions.
These changes are coupled because the first change causes
`fit-content(0)` tracks to participate in intrinsic sizing, while the
second ensures the base size from that sizing is not discarded during
clamping.
Rewrite
`increase_sizes_to_accommodate_spanning_items_crossing_flexible_tracks`
to follow spec steps more closely:
1. Process all items spanning flexible tracks together (not grouped by
span size), taking the maximum contribution per track
2. Distribute item contributions proportionally to flex factors
3. Subtract non-flexible tracks existing sizes from item contribution
before distributing to flexible tracks
When resolving grid placement like `grid-column: 1 / a`, the start
position from the line number was being incorrectly overwritten when
processing the end identifier. Now we only set start from end if the
start placement doesn't already have a line number.
No tests are affected by the change itself, but combined with the
upcoming commits it's going to result in the progress for
`grid-flex-track-intrinsic-sizes-002.html`.
This patch fixes an issue where grid items using `grid-area: <name>`
with no matching named grid area or lines would be incorrectly placed
at position 0.
According to https://www.w3.org/TR/css-grid-1/#line-placement:
1. When a `<custom-ident>` doesn't match any named line, placement
should fall back to the first implicit grid line
2. When the same `<custom-ident>` is given for both `grid-*-start` and
`grid-*-end` (which happens with `grid-area: name`), and both fall
back to the same implicit line, the resulting span is 1
Previously, the fallback values were hardcoded to 0 and 1, which placed
items in track 0. The fix changes the fallback to use
`m_explicit_line_count` (the first implicit line index) for both start
and end identifiers. When both reference the same line (start == end),
the existing "both positioned" logic now handles this by setting span=1
and adjusting end accordingly.
Use `calculate_inner_height()` and `calculate_inner_width()`, which
account for box-sizing, to resolve the item's size in max-content
contribution calculations.
Not every user of this requires an `auto` state, but most do.
This has quite a big diff but most of that is mechanical:
LengthPercentageOrAuto has `resolved_or_auto()` instead of `resolved()`,
and `to_px_or_zero()` instead of `to_px()`, to make their output
clearer.
We could skip doing item's intrinsic min-content layout if we know for
sure that there's no tracks with intrinsic sizing function to distribute
the min-content size to.
Now elements with position `absolute` properly resolve their position
inside parent elements with `grid`. I also imported some WPT tests
related to that topic.
Part 2 of resolving issues on https://hack4krak.pl
Fixes bug when we didn't use `tracks_to_grow_beyond_limits` and instead
distributed extra space to all affected tracks. Also implements missing
"when accommodating max-content" part.
...by another GFC. When searching for grid item that contains an
abspos box positioned relative to GFC, it's incorrect to assume that the
closest ancestor box whose parent establishes GFC is always the one we
are looking for, because there may be non-positioned GFC in between.
Fixes regression introduced in 80c8e78.
Before this change, `layout_absolutely_positioned_element()` in GFC
had an assumption that all contained by grid container abspos boxes were
also direct children of the grid container. This change adds handling
for the cases when it's not true and, in order to identify grid area
abspos box belongs to, we have to find ancestor grid item.
CSS grid specification states that for grid items with a replaced
element and a percentage preferred size or maximum size, the percentage
should be resolved against 0 during content-based minimum size
calculation. This makes sense, as it prevents replaced items from
overshooting their grid track while intrinsic track sizes are
calculated, and allows later track size resolution steps to scale
replaced items to fit their grid track.
FFC expects parent formatting context to mark size as definite if that's
the case, because otherwise it cannot figure cross line size correctly.
Fixes incorrect alignment when FFC is nested in GFC.
Progress on https://web.telegram.org/a/ layout.
This brings parsing of grid-row-* and grid-column-* properties (and
their associated shorthands) more inline with spec.
Changes:
- Only set omitted properties for combined-value shorthands (e.g.
`grid-row: a` rather than `grid-row: a / b`) if the single value is
`<custom-ident>`.
- `[ [ <integer [-∞,-1]> | <integer [1,∞]> ] && <custom-ident>? ]`:
- Properly resolve `calc`s for `<integer>` that rely on compute-time
information.
- `[ span && [ <integer [1,∞]> || <custom-ident> ] ]`
- Allow `calc`s for `<integer>`
- Allow `<custom-ident>`
There is still work to be done to properly use these parsed values.
Gains us 46 WPT tests.
`collapse_auto_fit_tracks_if_needed()` had a check that does collapsing
only if auto-fit is used like
`grid-template-columns: repeat(auto-fit, 1px);`, and it didn't work for
valid cases when `repeat(auto-fit)` is placed in the middle of
definition like `grid-template-columns: 1px repeat(auto-fit, 1px) 1px;`.
Spec says that definite grid container size should be used as free space
so there's no need to use `get_free_space()` that does iteration over
tracks and subtracts definite sizes from available space.
`getComputedStyle()` for grid tracks returns style value produced during
layout. This is needed to return resolved track sizes values which are
thrown away after layout is done. Now GFC produces more correct style
value by not ignoring grid line names.
Reimplements `grid`, `grid-template`, `grid-template-rows`, and
`grid-template-columns` in a way that uses a separate function for each
grammar rule defined in the specification. This change results in many
additional passing tests from the already imported WPT suite. Most of
the remaining test failures are related to incorrect serialization of
grid properties.
It was annoying to maintain two separate but almost identical functions
that gradually accumulated small differences over time. This change
replaces them with a single function that resolves either width or
height, depending on the specified dimension.
With this change we no longer stretch "width: auto" for replaced
elements and also use "width calculation rules for block-level replaced
elements", like suggested by the spec.
positioned element is a descendant of inline-block
Sets inline block offsets in InlineFormattingContext.cpp, but this is
not enough. When static position rect is calculated during layout,
not all ancestors of abspos box may have their offsets calculated yet
(more info here: https://github.com/LadybirdBrowser/ladybird/pull/2583#issuecomment-2507140272).
So now static position rect is calculated relative to static containing
block during layout and calculation relative to actual containing block
is done later in
FormattingContext::layout_absolutely_positioned_element.
Fixes wpt/css/CSS2/abspos/static-inside-inline-block.html
Instead of directly invoking `to_px()`,
`calculate_min_content_contribution()` needs to use
`calculate_inner_width()` and `calculate_inner_height()`, which are
aware of how to correctly handle `min-content` and `max-content` values.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/3469
