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serenity/Userland/Libraries/LibWeb/Layout/LineBuilder.h
Andreas Kling 64959a8504 LibWeb: Express intrinsic size layout via size constraints
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
2022-07-11 18:57:45 +02:00

63 lines
1.8 KiB
C++

/*
* Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibWeb/Layout/InlineFormattingContext.h>
namespace Web::Layout {
class LineBuilder {
AK_MAKE_NONCOPYABLE(LineBuilder);
AK_MAKE_NONMOVABLE(LineBuilder);
public:
LineBuilder(InlineFormattingContext&, FormattingState&, LayoutMode);
~LineBuilder();
void break_line();
void append_box(Box const&, float leading_size, float trailing_size, float leading_margin, float trailing_margin);
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(float next_item_width)
{
if (should_break(next_item_width)) {
break_line();
return true;
}
return false;
}
float available_width_for_current_line() const { return m_available_width_for_current_line; }
void update_last_line();
void remove_last_line_if_empty();
float current_y() const { return m_current_y; }
void adjust_last_line_after_inserting_floating_box(Badge<BlockFormattingContext>, CSS::Float, float space_used_by_float);
private:
void begin_new_line(bool increment_y);
bool should_break(float next_item_width);
LineBox& ensure_last_line_box();
InlineFormattingContext& m_context;
FormattingState& m_formatting_state;
FormattingState::NodeState& m_containing_block_state;
LayoutMode m_layout_mode {};
float m_available_width_for_current_line { 0 };
float m_current_y { 0 };
float m_max_height_on_current_line { 0 };
bool m_last_line_needs_update { false };
};
}