Normally we don't layout position:absolute elements until after the
parent formatting context has assigned dimensions to the current
formatting context's root box.
However, some of our parent contexts (especially FFC) don't do this
reliably, which makes position:absolute children have 0x0 dimensions.
Hack this for now by making ~BFC() pretend that the parent assigned
dimensions if it hadn't done it already.
Nobody makes undefined Lengths now, (although actually removing
Undefined will come in a later commit) so we can remove this parameter,
and `resolved_or_auto()`/`resolved_or_zero()`.
Until now, some formatting contexts (BFC in particular) have been
assigning size to the root box. This is really the responsibility of the
parent formatting context, so let's stop doing it.
To keep position:absolute working, parent formatting contexts now notify
child contexts when the child's root box has been sized. (Note that the
important thing here is for the child root to have its final used height
before it's able to place bottom-relative boxes.)
This breaks flexbox layout in some ways, but we'll have to address those
by improving the spec compliance of FFC.)
BFC currently has a number of architectural issues due to it being
responsible for setting the dimensions of the BFC root.
This patch moves the logic for setting up the ICB from BFC to Document.
This property represents the CSS content size, so let's reduce ambiguity
by using the spec terminology.
We also bring a bunch of related functions along for the ride.
Most of the time, we cannot resolve a `calc()` expression until we go to
use it. Since any `<length-percentage>` can legally be a `calc
()`, let's store it in `LengthPercentage` rather than make every single
user care about this distinction.
Block placement is now divided into a vertical and horizontal step. The
vertical step runs before formatting boxes internally. The horizontal
step still runs after (since we may need the final width value.)
This solves a long-standing architectural problem where IFC didn't know
its origin Y position within the BFC root box. This is required for
figuring out how to flow around floating objects. (Floating objects are
always relative to the BFC root.)
If we run out of horizontal space when placing floating objects,
we now perform a "break" and continue with a new line of floats
below the bottommost margin edge of the current line.
This is definitely not 100% to-spec yet, but a huge improvement
on ACID1 already. :^)
This patch adds a BFC::FloatSideData struct so we can contain left and
right floating object layout state in a struct. This is preparation for
adding more per-side state.
Despite looking like it was still needed, it was only used for passing
to other calls to Length::resolved() recursively. This makes the
various `foo.resolved().resolved()` calls a lot less awkward.
(Though, still quite awkward.)
I think we'd need to separate calculated lengths out to properly tidy
these calls up, but one yak at a time. :^)
A lot of this is quite ugly, but it should only be so until I remove
Length::Type::Percentage entirely. (Which should happen later in this
PR, otherwise, yell at me!) For now, a lot of things have to be
resolved twice, first from a LengthPercentage to a Length, and then
from a Length to a pixel one.
This was a hack to percentages within tables relative to the nearest
table-row ancestor instead of the nearest table container.
That didn't actually make sense, so this patch simply removes the hack
in favor of containing_block()->width().
We're using the outermost right and bottom child edges to determine the
width and height of the ICB. However, since these edges are *within* the
respective child's rectangle, we have to add 1 when turning them into
width and height values.
This fixes an issue where scrolling a document would shrink its viewport
rect by 1 pixel (on both axes) on every scroll step.
Per spec, the initial containing block (ICB) should have the size of the
viewport. We have only done this for the width until now, since we had
no way to express scrollable overflow.
This patch adds Layout::Box::m_overflow_data, an optional struct that
can hold on to information about a box's overflow. Then we have BFC
set the ICB up with some scrollable overflow instead of sizing it to fit
its content vertically.
This fixes a number of broken layouts where correctness depends on
having the appropriate ICB height.
Per the spec, only a BlockContainer" can have line boxes, so let's not
clutter up every Layout::Box with line boxes.
This also allows us to establish an invariant that BFC and IFC always
operate on a Layout::BlockContainer.
Note that if BlockContainer has all block-level children, its line boxes
are not used for anything. They are only used in the all inline-level
children scenario.
There's a subtle difference here. A "block box" in the spec is a
block-level box, while a "block container" is a box whose children are
either all inline-level boxes in an IFC, or all block-level boxes
participating in a BFC.
Notably, an "inline-block" box is a "block container" but not a "block
box" since it is itself inline-level.
The CSS spec uses the name "block formatting context root" when talking
about a box that establishes a BFC. So let's call it BFC::root() in our
code as well, instead of the less specific BFC::context_box().
Negative margins are a headache anyways, and allowing them to be
negative lead to weird behavior.
This patch avoids vasty wrong height-calculations by limiting the
allowed margins to positive numbers when evaluating the height of a
block.
Our "frame" concept very closely matches what the web specs call a
"browsing context", so let's rename it to that. :^)
The "main frame" becomes the "top-level browsing context",
and "sub-frames" are now "nested browsing contexts".
When computing the y-position of a clearing element, use the height of
the border box of the associated floating elements.
This also extracts this block of code to a helper lambda since it is
used twice.
This commit unifies methods and method/param names between the above
classes, as well as adds [[nodiscard]] and ALWAYS_INLINE where
appropriate. It also renamed the various move_by methods to
translate_by, as that more closely matches the transformation
terminology.
Now we use min-height for calculating the height of block boxes.
Besides, now we check if min-height/max-height are percentage values
and don't use them if parent's height isn't explicitly set (CSS 2.1
section 10.7).
Now we set margins, borders and paddings for floating boxes and include
them into calculating floating box positions by using margin_box() and
margin_box_as_relative_rect().
Height computation algorithm is actually
different for absolutely positioned boxes
and block formatting contexts (where it doesn't include floats)
Fixes#6408
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This commit fixes algorithm for computing auto height (CSS 2.2 10.6.7)
by including floating boxes into computation and implements one of the cases
for computing the height of absolutely positioned, non-replaced elements (10.6.4 rule 3)
Turns out compute_position should be invoked before placing the element
in normal flow. Otherwise, the position isn't set on the first layout.
The effect was that the block would "jump" into place on a secondary
layout.
This is a follow-up to commit:
deda7c8995
