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LibWeb: Express intrinsic size layout via size constraints

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Previously, we had three layout modes:

- Normal:
    - Everything uses the computed values from CSS.

- MinContent:
    - Containing blocks act as if they have 0 width.
    - All line breaking opportunities are taken.

- MaxContent:
    - Containing blocks act as if they have infinite width.
    - Only forced line breaks are accepted.

The above was based on a set of misunderstandings of CSS sizing.
A major problem with the above was that *all* containing blocks
behaved differently during intrinsic size layout, not just the
relevant one.

With this patch there are only two layout modes:

- Normal:
    - Everything uses the computed values from CSS.

- IntrinsicSizeDetermination:
    - One or more boxes have size constraints applied.

There are two size constraints per layout box, set here:

- FormattingState::NodeState::width_constraint
- FormattingState::NodeState::height_constraint

They are of type SizeConstraint and can be one of None, MinContent,
or MaxContent. The default is None.

When performing an IntrinsicSizeDetermination layout, we now assign
a size constraint to the box we're trying to determine the intrinsic
size of, which is then honored by using two new helpers to query
the dimensions of containing blocks:

- FormattingContext::containing_block_width_for(Box)
- FormattingContext::containing_block_height_for(Box)

If there's a relevant constraint in effect on the Box, the size of
its containing block is adjusted accordingly.

This is essentially an implementation of the "available space"
constraints from CSS-SIZING-3. I'm sure some things will break from
this, and we'll have to deal with that separately.

Spec: https://drafts.csswg.org/css-sizing-3/#available
This commit is contained in:
Andreas Kling 2022-07-09 15:17:47 +02:00
parent 66d08d2417
commit 64959a8504
13 changed files with 213 additions and 174 deletions
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6
Userland/Libraries/LibWeb/Layout/LineBuilder.h
View file

@ -23,9 +23,9 @@ public:
void append_text_chunk(TextNode const&, size_t offset_in_node, size_t length_in_node, float leading_size, float trailing_size, float leading_margin, float trailing_margin, float content_width, float content_height);
// Returns whether a line break occurred.
bool break_if_needed(LayoutMode layout_mode, float next_item_width)
bool break_if_needed(float next_item_width)
{
if (should_break(layout_mode, next_item_width)) {
if (should_break(next_item_width)) {
break_line();
return true;
}
@ -45,7 +45,7 @@ public:
private:
void begin_new_line(bool increment_y);
bool should_break(LayoutMode, float next_item_width);
bool should_break(float next_item_width);
LineBox& ensure_last_line_box();