Compute inline-block baselines by traversing into nested block children
to find the last in-flow line box, using correct offsets relative to the
margin box edge.
Also ensure inline-flex and inline-grid containers always derive their
baseline from content (per CSS Align), and add special handling for
<input> elements which have `overflow: clip` in the UA stylesheet but
should still align adjacent text with their internal content.
Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
Browsers such as Chrome and Firefox apply an arbitrary scale to the
current font size if `normal` is used for `line-height`. Firefox uses
1.2 while Chrome uses 1.15. Let's go with the latter for now, it's
relatively easy to change if we ever want to go back on that decision.
This also requires updating the expectations for a lot of layout tests.
The upside of this is that it's a bit easier to compare our layout
results to other browsers', especially Chrome.
When traversing the layout tree to find an appropriate box child to
derive the baseline from. Only the child's margin and offset was being
applied. Now we sum each offset on the recursive call.
This is a part of refactoring towards making the paintable tree
independent of the layout tree. Now, instead of transferring text
fragments from the layout tree to the paintable tree during the layout
commit phase, we allocate separate PaintableFragments that contain only
the information necessary for painting. Doing this also allows us to
get rid LineBoxes, as they are used only during layout.
This patch makes a few changes to the way we calculate line-height:
- `line-height: normal` is now resolved using metrics from the used
font (specifically, round(A + D + lineGap)).
- `line-height: calc(...)` is now resolved at style compute time.
- `line-height` values are now absolutized at style compute time.
As a consequence of the above, we no longer need to walk the DOM
ancestor chain looking for line-heights during style computation.
Instead, values are inherited, resolved and absolutized locally.
This is not only much faster, but also makes our line-height metrics
match those of other engines like Gecko and Blink.
This patch just adds the new root paintable and updates the tests
expectations. The next patch will move painting logic from the layout
viewport to the paint viewport.
Before this change, we always derived a box's baseline from its last
child, even if the last child didn't have any line boxes inside.
This caused baselines to slip further down vertically than expected.
There are more baseline alignment issues to fix, but this one was
responsible for a fair chunk of trouble. :^)
Using fixed-point saturated arithmetics for CSSPixels allows to avoid
accumulating floating-point errors.
This implementation is not complete yet: currently saturated
arithmetics implemented only for addition. But it is enough to not
regress any of layout tests we have :)
See https://github.com/SerenityOS/serenity/issues/18566
This patch does three things:
- Factors out the code that determines whether a box will create a new
formatting context for its children (and which type of context)
- Uses that code to mark all formatting context roots in layout tree
dumps. This makes it much easier to follow along with layout since
you can now see exactly where control is transferred to a new
formatting context.
- Rebaselines all existing layout tests, since the output format has
changed slightly.
If there is a remaining margin-bottom in margin collapsing state
tracker after laying out all boxes in the current BFC, it must be
assigned to the last in-flow child since margin collapsing cannot
occur across a formatting context boundary.
The current issue where margin-bottom may be counted twice due to
"collapse through" margins in the last in-flow child box is addressed
with this fix by excluding such boxes during the search for a box to
assign the remaining margin.
Test case coming with this fix has a layout bug with incorrectly
computed line height.
