Files
ladybird/Meta/Generators/generate_libweb_css_units.py

359 lines
11 KiB
Python

#!/usr/bin/env python3
# Copyright (c) 2025-2026, Sam Atkins <sam@ladybird.org>
# Copyright (c) 2026-present, the Ladybird developers.
#
# SPDX-License-Identifier: BSD-2-Clause
import argparse
import json
import sys
from pathlib import Path
from typing import TextIO
sys.path.append(str(Path(__file__).resolve().parent.parent))
from Utils.utils import snake_casify
from Utils.utils import title_casify
from Utils.utils import underlying_type_for_enum
def json_is_valid(dimensions_data: dict, json_path: str) -> bool:
is_valid = True
most_recent_dimension_name = ""
for dimension_name, units in dimensions_data.items():
# Dimensions should be in alphabetical order
if dimension_name.lower() < most_recent_dimension_name.lower():
print(
f"{json_path}: Dimension `{dimension_name}` is in the wrong position. "
"Please keep this list alphabetical!",
file=sys.stderr,
)
is_valid = False
most_recent_dimension_name = dimension_name
most_recent_unit_name = ""
canonical_unit = None
for unit_name, unit in units.items():
# Units should be in alphabetical order
if unit_name.lower() < most_recent_unit_name.lower():
print(
f"{json_path}: {dimension_name} unit `{unit_name}` is in the wrong position. "
"Please keep this list alphabetical!",
file=sys.stderr,
)
is_valid = False
most_recent_unit_name = unit_name
is_canonical_unit = unit.get("is-canonical-unit") is True
number_of_canonical_unit = unit.get("number-of-canonical-unit")
relative_to = unit.get("relative-to")
provided_count = (
(1 if is_canonical_unit else 0)
+ (1 if number_of_canonical_unit is not None else 0)
+ (1 if relative_to is not None else 0)
)
if provided_count != 1:
print(
f"{json_path}: {dimension_name} unit `{unit_name}` must have exactly 1 of "
"`is-canonical-unit: true`, `number-of-canonical-unit`, or `relative-to` provided.",
file=sys.stderr,
)
is_valid = False
if is_canonical_unit:
if canonical_unit is not None:
print(
f"{json_path}: {dimension_name} unit `{unit_name}` marked canonical, "
f"but `{canonical_unit}` was already. Must have exactly 1.",
file=sys.stderr,
)
is_valid = False
else:
canonical_unit = unit_name
if relative_to is not None:
if dimension_name == "length":
if relative_to not in ("font", "viewport"):
print(
f"{json_path}: {dimension_name} unit `{unit_name}` is marked as relative to "
f"`{relative_to}`, which is unsupported.",
file=sys.stderr,
)
is_valid = False
else:
print(
f"{json_path}: {dimension_name} unit `{unit_name}` is marked as relative, "
"but only relative length units are currently supported.",
file=sys.stderr,
)
is_valid = False
if canonical_unit is None:
print(
f"{json_path}: {dimension_name} has no unit marked as canonical. Must have exactly 1.",
file=sys.stderr,
)
is_valid = False
return is_valid
def canonical_unit_name(units: dict) -> str:
for unit_name, unit in units.items():
if unit.get("is-canonical-unit") is True:
return unit_name
raise ValueError("No canonical unit found")
def write_header_file(out: TextIO, dimensions_data: dict) -> None:
out.write("""
#pragma once
#include <AK/FlyString.h>
#include <AK/Optional.h>
namespace Web::CSS {
""")
enum_type = underlying_type_for_enum(len(dimensions_data))
out.write(f"enum class DimensionType : {enum_type} {{\n")
for name in dimensions_data:
out.write(f" {title_casify(name)},\n")
out.write("""
};
Optional<DimensionType> dimension_for_unit(StringView);
""")
for dimension_name, units in dimensions_data.items():
name_titlecase = title_casify(dimension_name)
name_snakecase = snake_casify(dimension_name)
unit_enum_type = underlying_type_for_enum(len(units))
canonical = title_casify(canonical_unit_name(units))
out.write(f"""
enum class {name_titlecase}Unit : {unit_enum_type} {{
""")
for unit_name in units:
out.write(f" {title_casify(unit_name)},\n")
out.write(f"""
}};
constexpr {name_titlecase}Unit canonical_{name_snakecase}_unit() {{ return {name_titlecase}Unit::{canonical}; }}
Optional<{name_titlecase}Unit> string_to_{name_snakecase}_unit(StringView);
FlyString to_string({name_titlecase}Unit);
bool units_are_compatible({name_titlecase}Unit, {name_titlecase}Unit);
double ratio_between_units({name_titlecase}Unit, {name_titlecase}Unit);
""")
out.write("""
bool is_absolute(LengthUnit);
bool is_font_relative(LengthUnit);
bool is_viewport_relative(LengthUnit);
inline bool is_relative(LengthUnit unit) { return !is_absolute(unit); }
}
""")
def format_ratio(value) -> str:
# JSON ints render as ints, floats as floats (matching String::number output).
return str(value)
def write_implementation_file(out: TextIO, dimensions_data: dict) -> None:
out.write("""
#include <LibWeb/CSS/Units.h>
namespace Web::CSS {
Optional<DimensionType> dimension_for_unit(StringView unit_name)
{
""")
for dimension_name, units in dimensions_data.items():
name_titlecase = title_casify(dimension_name)
out.write(" if (")
first = True
for unit_name in units:
if first:
first = False
else:
out.write("\n || ")
out.write(f'unit_name.equals_ignoring_ascii_case("{unit_name}"sv)')
out.write(f""")
return DimensionType::{name_titlecase};
""")
out.write("""
return {};
}
""")
for dimension_name, units in dimensions_data.items():
name_titlecase = title_casify(dimension_name)
name_snakecase = snake_casify(dimension_name)
canonical = title_casify(canonical_unit_name(units))
out.write(f"""
Optional<{name_titlecase}Unit> string_to_{name_snakecase}_unit(StringView unit_name)
{{
""")
for unit_name in units:
out.write(f"""
if (unit_name.equals_ignoring_ascii_case("{unit_name}"sv))
return {name_titlecase}Unit::{title_casify(unit_name)};""")
out.write(f"""
return {{}};
}}
FlyString to_string({name_titlecase}Unit value)
{{
switch (value) {{""")
for unit_name in units:
out.write(f"""
case {name_titlecase}Unit::{title_casify(unit_name)}:
return "{unit_name}"_fly_string;""")
out.write(f"""
default:
VERIFY_NOT_REACHED();
}}
}}
bool units_are_compatible({name_titlecase}Unit a, {name_titlecase}Unit b)
{{
auto is_absolute = []({name_titlecase}Unit unit) -> bool {{
switch (unit) {{
""")
# https://drafts.csswg.org/css-values-4/#compatible-units
for unit_name, unit in units.items():
if "relative-to" in unit:
continue
out.write(f" case {name_titlecase}Unit::{title_casify(unit_name)}:\n")
out.write(f"""
return true;
default:
return false;
}}
}};
return is_absolute(a) && is_absolute(b);
}}
double ratio_between_units({name_titlecase}Unit from, {name_titlecase}Unit to)
{{
if (from == to)
return 1;
auto ratio_to_canonical_unit = []({name_titlecase}Unit unit) -> double {{
switch (unit) {{
""")
for unit_name, unit in units.items():
if "relative-to" in unit:
continue
ratio = unit.get("number-of-canonical-unit")
if ratio is not None:
ratio_str = format_ratio(ratio)
else:
# This must be the canonical unit, so the ratio is 1.
ratio_str = "1"
out.write(f"""
case {name_titlecase}Unit::{title_casify(unit_name)}:
return {ratio_str};
""")
out.write(f"""
default:
// `from` is a relative unit, so this isn't valid.
VERIFY_NOT_REACHED();
}}
}};
if (to == {name_titlecase}Unit::{canonical})
return ratio_to_canonical_unit(from);
return ratio_to_canonical_unit(from) / ratio_to_canonical_unit(to);
}}
""")
# Length-specific functions
length_units = dimensions_data["length"]
out.write("""
bool is_absolute(LengthUnit unit)
{
switch (unit) {
""")
for unit_name, unit in length_units.items():
if "relative-to" in unit:
continue
out.write(f" case LengthUnit::{title_casify(unit_name)}:\n")
out.write("""
return true;
default:
return false;
}
}
bool is_font_relative(LengthUnit unit)
{
switch (unit) {
""")
for unit_name, unit in length_units.items():
if unit.get("relative-to") != "font":
continue
out.write(f" case LengthUnit::{title_casify(unit_name)}:\n")
out.write("""
return true;
default:
return false;
}
}
bool is_viewport_relative(LengthUnit unit)
{
switch (unit) {
""")
for unit_name, unit in length_units.items():
if unit.get("relative-to") != "viewport":
continue
out.write(f" case LengthUnit::{title_casify(unit_name)}:\n")
out.write("""
return true;
default:
return false;
}
}
}
""")
def main():
parser = argparse.ArgumentParser(description="Generate CSS Units", add_help=False)
parser.add_argument("--help", action="help", help="Show this help message and exit")
parser.add_argument("-h", "--header", required=True, help="Path to the Units header file to generate")
parser.add_argument(
"-c", "--implementation", required=True, help="Path to the Units implementation file to generate"
)
parser.add_argument("-j", "--json", required=True, help="Path to the JSON file to read from")
args = parser.parse_args()
with open(args.json, "r", encoding="utf-8") as input_file:
dimensions_data = json.load(input_file)
if not json_is_valid(dimensions_data, args.json):
sys.exit(1)
with open(args.header, "w", encoding="utf-8") as output_file:
write_header_file(output_file, dimensions_data)
with open(args.implementation, "w", encoding="utf-8") as output_file:
write_implementation_file(output_file, dimensions_data)
if __name__ == "__main__":
main()